Conservation of Wall Painting Department COURTAULD...

Conservat ion o f Wal l Paint ing Department

COURTAULD I N STITUTE OF ART

Somerset House, Strand, London WC2R 0RN Telephone +44 (0)20 7848-2848 [email protected]

This is a dissertation accepted for a Postgraduate Diploma in the

Conservation of Wall Painting in the Conservation of Wall Painting Department, Courtauld Institute of Art, University of London.

It is unpublished and

copyright is held by the author. No quotations or information derived from it

may be published without the prior written consent of the author,

who may be contacted through the address above.

AN INVESTIGATION OF THE USE OF SOLVENT GELS FOR

THE REMOVAL OF WAX-RASED COATINGS FROM WALL PAINTINGS

TOBIT CURTEIS

Courtauld Institute ofArt/Getty Conservation Institute,

Conservation of Wall Paintings Department.

July 1991

CONTENTS

Acknowledgements.

1. Summary.

2. Introduction.

3. Solvent Gel Principles.

4. Gel Components.

4.1 Carbopol

4.1.1 Thickening mechanisms of Carbopol.

4.1.2 Amines for Neutralisation.

4.1.3 Surfactants.

4.1.4 Clearance.

4.1.5 Possible drawbacks with Carbopol.

4.2 Pemulen.

4.2.1 Thickening mechanisms of Pemulen.

4.2.2 Drawbacks of Pemulen.

4.3 Cellulose materials

5. Desiderata for Test Sites.

6. Test Methodology and Procedure.

6.1 Examination and Analysis.

6.2 Preparation of Carbopol gels.

6.3 Test Procedure.

6.4 Clearance Tests.

7. Holcot Church.

7.1 Introduction.

7.2 Painting Condition.

7.3 Cross-section analysis and SEM.

7.4 FTIR and Thermomicroscopy.

7.5 Solvency parameter tests.

7.6 Solvent gel tests.

8. The Holy Sepulchre Chapel,

Winchester Cathedral.

8.1 Introduction.

8.2 Technique.

8.3 Conservation History.



8.6 FITR and Thermomicroscopy.



9. Westminster Abbey Chapter House.

9.1 Introduction.

9.2 Technique.

9.3 Conservation History.

9.3.1 G. G. Scott.

9.3.2 Prof A. H. Church

9.3.3 H. M. Office of Works.

9.3.4 English Heritage.



9.5.1 Binding Media.

9.6 FTIR and Thermomicroscopy.



10. Analysis for Residual Materials.

11. Conclusion and Further Research.

12. Bibliography.

13. Appendices.

1. Recipes for wax and wax resin

preservatives advocated byProfessors Church and Tristram.

2. Solvent Gel formulas.

3. Teas Chart showing the solvency

parameters of the most effective

solvent gels in relation to the

solubility region of beeswax.

4. Solvent Gel Tests,Summary of

results reported in the proformas.

5. Fourier Transform Infrared Spectra.

6. Nitromors paint stripper.

7. Solvent Gel Tests Carried out in the

Chapel Of Our lady Undercroft,

Canterbury Cathedral.

8. Site proformas.

14. Plates.

Acknowledgements

For permission to examine and sample the paintings at the four sites studied I am

grateful to the Dean and Chapter of Canterbury Cathedral and to Mr. Wolfgang

Gartner of the Wallpaintings Workshop; the Dean and Chapter of Winchester

Cathedral and especially to Mr. John Hardacre for his help and advice, the Parish

Council of Holcot Church and the Rev. Anthony Watkins; and to Mr. Jan Keevil,

Head of the English Heritage Conservation Studio, for Westminster Abbey Chapter

House.

For technical information on materials and for product samples I would like to

thank Mr. G. Stead and Mr. John Gallagher of B. F. Goodrich and Mr. C. Drake of

AKZO Chemicals. Ms. Zahira Veliz, Mr. Alan Phenix (Courtauld Institute) and Ms.

Lucia Scalisi (Victoria and Albert Museum) gave much helpful advice on

formulation of the gels.

I am particularly grateful to Ms. Marianne Odlyha of Birkbeck College for her

constant help and valuable advice especially in regard to the analysis including

Fl'lK, DSC and Thermomicroscopy. I am also very grateful for the help of Mr.

Raymond White, Scientific Department, National Gallery, particularly in the area of

interpretation of IR spectra.

For their advice and support throughout and in all areas of this research I would

especially like to thank my two supervisors Ms. Aviva Burnstock, Scientific

Department, National Gallery, who also carried out the SEM and EDX analysis,

and Ms. Katherine Powell of the Courtauld Institute.

Finally I would like to thank Mr David Park and Ms. Sharon Cather of the

Courtauld Institute for their continual help during the course of this work.

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Summarv

The effects of the preservative' coatings commonly applied to wall paintings in the19th and first half of the 20th centuries, have been both damaging and disfiguring in

the longer term. Typically these coatings consist of either pure beeswax or a mixture

of beeswax and a natural resin applied to the painting surface. The penetration of

the coatings due to the porosity of wall paintings and the fragile nature of many ofthe paint surfaces, when treated, has made the removal of such materials extremely

difficult.

The solvent gels formulated for this study were intended to have very specific

solvency parameters allowing them to dissolve a particular material, without

endangering the other vulnerable components of the paint surface. The system was

not be intended as an all-encompassing solvent mixture for the removal of all

coatings on the paint surface. If there were more than one coating of a different

nature, for instance a varnish layer covered by a wax resin coating, it would be

necessary to use two different gels, each tailored by their solvent mixtures to the

specific problem of each layer.

The complete removal from the painting of all components of the gel system, forms

an integral part of gel cleaning process. The long-term effects of the non-volatile

components and their interaction with the materials of wall paintings are not fully

understood and to ensure that no damage is caused by these materials the

implementation of an adequate system of clearance must be undertaken.

The investigations into the feasibility of such a cleaning system drew heavily on the

work of Richard Wolbers who was responsible for developing the theory andformulating a range of organic solvent gel systems for particular cleaning problems

in the field of easel painting conservation. The formulas developed by him providedthe starting point for the development of a series of solvent gels that were applicableto the problems faced in wall paintings.

Materials were chosen that had a known history of usage in general conservation,

although some of these had not been applied to wall painting conservation. Much ofthe initial work was theoretical, involved with the chemistry of producing a gelsystem with the necessary attributes. The main gelling agent, a high molecular

weight polyacrylic acid, Carbopol, was chosen due to its ability to effect very viscousgels at relatively low percentages. Due to the high wax component of the coatings itwas necessary to produce a series of highly aromatic solvent gels. A program of tests

was undertaken on a number of wall paintings that had been treated with a wax or

wax/resin coating in order to evaluate both the cleaning effect of the gels and theirsubsequent clearance. The possibility of conducting the tests on laboratory modelswas evaluated, but despite the complications caused by the lack of chemical controlon actual paintings, it was felt that due to the problems of reproducing the necessaryconditions on a model, the results obtained from actual paintings would of be morevalue in examining the effects of the gels.

Cross-sections were taken to establish the stratigraphy of both the coatings and thepainting. This enabled the characterisation of differing surface coatings and thetheir relative thickness to be established in order to make a comparison with the

situation after cleaning. These samples were examined both on the surface and incross-section using visible and ultra-violet microscopy and scanning electronmicroscopy. Samples of the surface coating were analysed using FTIR in order toestablish the exact nature of the material. This was necessary so that the solvent

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component of the gel could be prepared to dissolve that particular material.

After the cleaning and clearance tests had been carried out, further samples weretaken in order to evaluate the effects of the gels as well as to check for possible

residues. Examination was carried out using visible, ultra violet and scanningelectron microscopy. In order to examine the problem of clearance more fully,controlled tests were carried out on a laboratory model, allowing a more detailed

series of experiments to take place.

The results of the project were extremely encouraging indicating that it is possible to

produce a solvent gel system with the necessary solvency parameters to remove thecommonly encountered wax coatings. No residues of the material from the cleaningsystem were detected with FTIR or SEM after clearence had taken place. This latterresult must however be qualified. A negative result such as this means simply thatno residue has so far been found, it is not a guarantee that no trace of the material ispresent and further more sensitive analysis should be carried out to ensure this.

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2. Introduction

During the nineteenth and the first half of this century, wax and resin based

treatments were commonly believed to be the most effective method for the

'preservation' of wall paintings. The original premise behind the application of such

coatings lay in the mistaken belief that classical Roman paintings were executed in

encaustic technique, thus leading to the conclusion that wax was responsible for

their longevity and survival. The writings of both Pliny and Vitruvius appeared to

confirm that the use of wax was advantageous in protecting fresco paintings.1

The saturation of the painting with such coatings was seen as a general cure for the

various types of damage encountered and with the active involvement of respected

men such as Professors E. W. Tristram and A. H. Church, who were regarded as

authorities on such matters, became the accepted treatment for almost all wall

paintings. An application of such a coating effectively restored cohesion to

powdering surfaces, and was equally effective at readhesion of flaking layers.

Perhaps the effect which was initially most apparent was the immediate visual

change caused by the saturation of the paint layer. The result was to change wall

paintings from damaged'and apparently faded objects into bright, sound decorative

elements more in keeping with the contemporary aesthetic.

Such effects were relatively short term, and it soon became apparent that the use of

wax and resin coatings was the major cause of the damage that began to appear on

paintings. Serious discoloration and flaking were seen to occur. This damage fell

broadly into two categories, aesthetic and structural. The aesthetic alteration

brought about by such coatings are often the most noticeable forms of damage. Pure

beeswax is a very stable polymer, that does not discolor or break down with age. The

main reason beeswax coatings appear to darken is that at room temperatures the

1 Cather & Howard 1986

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wax is relatively soft,2 and will absorb atmospheric dirt that settles on it, including

the byproducts of the burning of fuels such as oil and coal (commonly used in the

past to fuel heating systems in parish churches), which will remain fixed to the

surface of the wax, thereby obscuring the painting. A further reason for the

discoloration is that some of the preservative coatings consisted of a mixture of wax

and a natural resin such as copal.3 During the oxidization and aging process of

natural resins darkening occurs, thus further obscuring the paint surface.

The main reason for the physical damage caused by these coatings relates to the

porous nature of lime-based wall paintings. This porosity allows moisture and water-

soluble materials such as salts to move freely through the structure of the painting.

If this porosity is significantly reduced by the application of an impermeable coating

over the surface of the painting the effect will be to set up internal stresses within

and below the paint layer. Soluble salts that would have crystallised on the surface

of the painting causing little or no physical damage will now crystallise in the

restricted space of the pores below the surface. The expansion of volume that occurs

in the process of crystallisation will cause the pores to break and thus disrupt the

paint surface causing both decohesion and delamination. The application of wax

based coatings to oil or secco paintings was in some ways potentially less damaging.

Due to the nature of the medium, such paintings were far less porous than lime-

based wall paintings, and therefore a coating of wax would not considerably alter the

rate of penetration of moisture. The damage caused in these cases is aesthetic with

the darkening of the coating, described above, obscuring the paint surface.

It was not until 1953 when the committee set up by the Council for the Care of

Churches (CCC) to examine the practices employed in the conservation of wall

2 The glass transition temperature of beeswax is

3 Appendix 8.

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paintings, published a letter in the Times denouncing the use of '....Wax or any other

surface coating which may impeded the free evaporation of any moisture...' that the

damage caused by the practice was generally acknowledged.4 In 1959 the CCC

published a full report on the subject setting out the damaging effects caused by

such 'preservative' treatments and advising against their use.5

Traditional methods for the removal of these coating have relied on the use of

strongly acting organic solvents which aim to remove all components of the surface

coatings through the application of a single type of cleaning agent. The advantages

of organic solvents supported in a gel system rather than as free and highly volatile

agents have long been apparent to conservators.6 The most commonly used cleaning

system in recent years has been Nitromors, a commercially available paint stripper.

The formula for this product has changed a number of times since it was first

introduced in the early 1940s, but its main components have altered little and have

always been based on a mixture of methanol and dichloromethane supported in a

gelling medium containing both paraffin wax and a small component of cellulose.7

The disadvantages of such a material are twofold. The first is that a commercial

paint stripper such as this is intended to encompass the removal of as wide a range

of organic material possible. The structures of wall paintings can be very complex

with a number of delicate and soluble layers. Such a material will not only dissolve

the wax and resin coatings, but also any other vulnerable organic components such

as surface glazes and medium found in secco wall paintings. The second

disadvantage lies with the components of the material themselves. For a long period

of time, Nitromors has been used without a full knowledge of its chemical

4 The Times, 21st February 1953.5 Central Council for the Care of Churches, 1959.6 The use of gels in wall painting conservation is not limited to organic solvents. The use of AB 57, acombination of sodium and ammonium bicarbonates in a cellulose gelling medium, is a well

established treatment for the removal of insoluble salts. Mora, Mora and Philippot 1984. pp.342.

7 Appendix 6.

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components or the possible effects of chemical decomposition that may occur in the

longer term if any of the material is left on the painting. A commercially available

paint stripper would tend to be concerned with the short-term effects of the material

and not the longer term that would be of concern to the conservator.

3. Solvent Gel Principles

The principles behind the use of a gel system to alter the working properties of

organic solvents has clear advantages in areas of conservation. The gel support

reduces the rate of evaporation and diffusion of the solvent mixture in which it is

dissolved by increasing the viscosity of the system thus enabling an increased contact

period in a discrete localised area of the surface of the object. The result of this

reduction in solvent volatility is to 'concentrate' the effect of the solvent, increasing

the ability to more effectively dissolve the material on which it is working. There is

no evidence that the use of a gel support alters the solubility parameters of the

solvent, simply that within those parameters the action of the solvent appears to be

enhanced. The direct application of this phenomenon is that where a 'strong' free

solvent (a solvent with a solubility parameter in the center of the region of the

solute), would be required the same effect could be achieved using a ^weaker'

solvent (one with a solubility parameter towards the edge of the of the region of the

solute) supported in a gel system. Containing the solvent in such a way might also

reduce the amount of undercutting, as discussed by Burnstock and White,8 that can

occur when there is no control over the penetration of a free solvent. This is of

course an advantage when dealing with complex layer structures of soluble organic

materials as it allows far more specific solubility to be achieved, more readily

allowing the removal of individual layers with potentially less 'strong' and hazardous

solvents.

8 Burnstock and White 1990.

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Recently significant advances have been made with the application of such gels to

cleaning problems encountered on easel paintings through the work of Richard

Wolbers. His use of an acrylic acid polymer, Carbopol, as a gelling agent for organic

solvents marked a significant advance on the use of the cellulose materials more

commonly used.9 Carbopol had the advantage of producing a thixotropic viscous gel

at a very low percentage due to its high swelling ability and could more easily be

used in conjunction with a wide range of solvents. Wolbers developed the rationale

for the use of such gel systems with very specific parameters to work on individual

parts of a particular cleaning case, rather than on the case as a whole.

The application of these principles to the removal of wax and wax/resin coatings

from wall paintings was clearly desirable as the problems associated with the

removal of soluble materials encountered in this field of conservation are complex.

The most important difference between easel paintings and wall paintings in terms

of surface is the high level of porosity and topography of many wall paintings. The

effect of this is that at the interface with the paint surface, there is no longer the

relatively discrete separation between coating and pigment layer encountered on

easel paintings, but with a coating that penetrates the surface to various depths,

becoming an almost integral part or the matrix of pigment and binder. The degree

to which this occurs depends on the nature of the painting technique and its

condition. In cases where there is decohesion occurring within the paint layers this

situation is further complicated. The problem is further complicated by the method

in which the coating was applied. In many cases this was carried out using heat

treatments in order to drive the material deep into the painting in the belief that the

greater the penetration, the more stable the treatment.10

9 HPMC is used by Wolbers as a support for resin soaps and enzyme cleaning systems.10 Appendix 1.

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The ability to finely control solvency parameters offered by gels has a number of

further advantages which apply in all fields of painting conservation, but are

particularly important in the field of wall paintings. First among these is the scope

for a reduction in toxicity of the solvents used. In many cases when free solvents are

used it has been necessary to use those with relatively high levels of toxicity to gain

the solvency parameters required. The use of large quantities of dichloromethane

with a MEL of 350 mg/m3 and LD 50 of 2136 mg/kg oral, ratn both free and in

Nitromors paint stripper, is the standard method for the removal of wax coatings

from English wall paintings.12 Using solvents in a gel system a similar area of

solvency can often be achieved with a less toxic solvent. The toxic effect on the

conservator would also be limited due to the reduction in evaporation rate of the

solvent caused by the gel.

A further advantage in the use of solvent gels is the reduction in mechanical action

on the paint layer from that caused by continual swab rolling with free solvents.

Solvent gels are applied to the wall with a swab and then gently moved, until they

area removed with a second swab. Contact between the surface of the painting and

the swab is minimal. Such mechanical action as there is can be further reduced by

the use of an intervention layer of a permeable material such as Japanese tissue

between the gel and the paint layer, thus reducing the risk of damage when working

on a damaged or delicate surface. The use of an intervention layer also acts as a

considerable aid in the removal of the majority of the gel from the surface of the

painting.

An essential part of the cleaning process using solvent gels is the clearance

11BDH Hazard Data Sheets. MEL or Maximum Exposure Limit is taken from the HSE guidance

note EH40, 'Occupational Exposure Limits', and is an indication of the maximum amount of thematerial that it is considered acceptable to be exposed to. LD or Lethal Dose indicates the toxicityof a material on a rat or mouse (as stated) as a guide to its toxic effect on humans.

12Ballantyneetal. 1988

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procedure that must be undertaken in order to remove all residues of the gel from

the painting. Although a number of recent studies have examined the possible

effects of some residual materials,13 the long-term effects of many of the gel

components and any interaction with the materials of the painting have not been

fully examined. The complete removal of residual material must therefore form an

integral part of the overall cleaning method.

4. Gel Components

The two basic components necessary for a solvent gel are the gelling agent and the

solvents themselves. Further components are subsidiary to these in that they are

specific to a particular gelling agent (or solvent) and are intended either to make

the solvent and the gelling agent compatible, or to alter the effect of the gel on the

solute. Into this secondary category can be placed surfactants, pH buffers and

neutralising mechanisms. It is principally, therefore, the choice of gelling agent

which dictates the nature of other components in the solvent gel.

4.1 Carbopol™

Carbopol resins are long-chain acrylic acid polymers cross-linked with a polyalkenyl

polyether (carboxy polymethylene), with pH of 2.5-3.0 in a 1% water dispersion.14

Carbopol in its undissolved state is a white powder consisting of tightly coiled long-

chain molecule. When it undergoes certain reactions, the molecule uncoils, thus

causing the viscosity of the solution to rise. It is available in a wide range of

molecular weights ranging from approximately 450,000 (Carbopol 907) to 4,000,000

(Carbopol 940).15 The molecular weight affects the surface tension and viscosity of

the final product therefore it is important that the most suitable one is chosen to

13 Wolbers 1990A, Burnstock and White 1990.14 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio.15 Molecular weights given by the manufacturers are approximate. Carbopol 907 = 450,000,Carbopol 910 = 750,000, Carbopol 941 = 1,250,000, Carbopol 934 = 3,000,000, Carbopol 940 =4,000,000. (Carbopol 954 mw 3,000,000 is no longer widely available.)

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achieve optimum performance for the solvent gels.16

Carbopol 934 or 940 were chosen as the most suitable gelling agents for the gels

tested in this project due particularly to their ability to produce the necessary high

levels of viscosity at very low percentages. They were also adaptable to all the

solvent mixtures required, both polar and non-polar, for the cleaning of wall

paintings.

Fig.l. Structural Formula of Carbopol

4.1.1 Thickening Mechanisms of Carbopol.

Although Carbopol resins are predominantly hydrophilic they can also be used in

non-aqueous solvent systems. There are two basic methods for using Carbopol as a

thickening agent. The first, the hydrogen bonding method, can only be employed in

polar systems, while the second, the neutralisation method, is suitable for both polar

and non-polar systems.

Hydrogen Bonding.

This system requires the use of a solvent capable of donating an hydroxyl group. The

resulting hydrogen bonds between the carboxyl groups of the Carbopol and the

hydroxyl groups of the solvent donor will cause the molecule to uncoil and

thickening to occur. The solvents capable of this are limited to polyhydroxy, and

polyethoxy solvents such as diols, triols and polyols. This process is far slower than

16 Carbopol 934 and 940 were found to be the most efficient in terms of the low percentage

required to produce the desired viscosity for the solvent gels.

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the neutralisation method and it may take a number of hours for full thickening to

occur. Empirical observation through experimentation undertaken in the course of

this work has shown that this process does not achieve the viscosity of neutralised

systems using the same percentage volume of Carbopol. A further problem for this

study is that the use of the necessary hydroxyl donor solvents may adversely effect

the solubility parameters required for the particular gel.

Fig.2. Schematic Depiction of a Molecule of Carbopol in its

uncoiled state with hydrogen bonding.

V

Neutralisation.

For this method the resin is neutralised by the use of a base to produce a salt

soluble in the required solvents. In an aqueous or polar solution this can be

achieved using a base such as ammonium or sodium hydroxide. A 3% aqueous

solution of Carbopol can produce a viscosity of 30,000 to 40,000 cP without

neutralisation. A level of viscosity from 40,000 to 60,000 can be produced by a 0.5%

solution of Carbopol in water after neutralisation to pH 7 - 7.8 with sodium

hydroxide.17 In a non-polar solvent system (such as those considered in these tests)

or in one where the use of these bases is undesirable the resin can be neutralised in

the same way with an amine.18

17 Goodrich B.F. CARBOPOL Water Soluble Resins. Technical data. Ohio, pp 13-1418 The use of sodium hydroxide as part of a cleaning system for wall paintings is consideredundesirable as the free sodium ions introduced into the wall will readily react with other free ions

producing highly soluble salts which are inherently dangerous to wall paintings. Ammonium

hydroxide is sometimes used for cleaning wall paintings, and it is possible that it could also be use

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The pH of the overall gel is not only important for the effect it may have on the

paint surface, but also for the stability of the gel.19 It was possible that during the

cleaning process the dissolved material from the surface of the painting may cause

the pH of the gel to alter to an extent that it would break down. The use of a pH

buffer was considered to counter this effect. Buffers are solutions that will enable

the main solution to retain a constant pH when small quantities of acids or bases are

added. Empirical experiments were carried out to establish whether the pH of the

gel was altered, during its application, to an extent where the use of a buffer solution

would become necessary.20 The results showed that the alteration in the pH of the

gel was negligible. It remained physically stable throughout the test, even when

applied to a volume of wax far greater than that which would be encountered in the

field.

Fig.3. Schematic Depiction of a Molecule of Carbopol in its

uncoiled state after neutralisation with ammonium hydroxide.

4.1.2 Amines for Neutralisation.

For the purposes of this study it was necessary to work with aromatic and aliphatic

as the neutralising agent in a polar solvent gel, without risk to the paintings.19 The pH of the gels formulated for this work was approximately 7.5.20 The pH of the solvent gel was tested in its fresh state. A given quantity of beeswax was thendissolved in the gel and a second test for pH was made. These were found to be the same.

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hydrocarbon solvents in order to obtain the required solvency parameters to remove

wax-based materials. The use of a neutralising mechanism offered the most

adaptable and viscous gel, and the non-polar solvents were not suitable for

hydrogen bonding. It was therefore necessary to use an amine that would produce a

Carbopol salt soluble in aromatic and aliphatic hydrocarbon solvents.

A wide range of amines were examined and/or tested as possible neutralising agents

for the gels.21 Ethomeen C-25, (polyoxyethylene(15)cocoamine) and Ethomeen C-

12, (Cocobis(2-hydroxethyl)amine) appeared to offer the most efficient

neutralisation enabling the Carbopol to be dissolved in the required aromatic

solvents22. However after extensive testing Ethomeen C-12 proved to be the most

effective of the two at the lowest percentages.23 Virtually insoluble in water, it is

readily dissolved in aromatic solvents, and has a relatively low cationic surfactant

HLB value of 10 compared to that of 19 for Ethomeen C-25.24 It also has the added

advantage of relatively low toxicity with an LD 50 of 1500 mg/kg.25

Fig.4. Structural Formula of Ethomeen C-12

CH2.CH2.OH

R-N (R = Coco alkyl)

CH2.CH2.OH

The fact that Ethomeen C-12 is not only an amine but also a surfactant, albeit a

21 Those considered included Ethomeen C-12, Ethomeen C-25, Armeen-OD (products ofAKZOChemicals), Dodecylamine & Triethanolamine.

22 xylene and White Spirit.23 Tests using Ethomeen C-12 to gel Carbopol with aromatic systems have already been carried outby a several easel painting conservators, showing successful results had depended on the use of very

exact amounts. (Pers. comm. Lucia Scalisi and Alan Phenix)

24 Hydrophile/Lipophile Balance value. The HLB value is a scale used to compare the relativeemulsifying properties of surfactants. It runs from 0 to 40 (0 is the weakest) and is established by

either experimental or mathematical methods.

25 AKZO Chemicals.

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mild one, is of concern due to the possible problems of clearance that might be

presented.

4.1.3 Surfactants.

By forming bonds between polar and non-polar materials surfactants reduce the

surface tension between the gel and the solute increasing the intimate surface

contact (Vetting') and thereby increasing both the homogeneity and the potency of

the cleaning action.26 This same action could also cause greater penetration of the

substrate resulting in problems of clearance. The inclusion of a suitable surfactant in

a gel can also allow the addition of a solvent that is not miscible with the main

solvent, thus permitting a fine manipulation of the solubility parameters of the

overall system, however the surfactant may itself alter the solubility parameters of

the gel.

The possible problems involved with the use of surfactants in painting conservation

have been the subject of a number of recent discussions.27 All of these have

concentrated on the effect of surfactants on easel paintings, and while many of these

also occur on wall paintings, there are further complications associated with wall

paintings. Most important of these are the effects of the surfactant on the irregular

topography and porous substrate typical of wall paintings. Due to the ability of

surfactants to reduce surface tension there is a greatly increased tendency to

penetrate the painting to some depth. The danger that this could result in the

surfactant remaining within the substrate, avoiding the clearance procedure, is

present in all paintings, however the open structure of wall paintings makes it all the

more acute. The long-term results of this are unclear and it appears probable that

the presence of a residual surfactant could increase the hydrophilic tendency of the

26 This effect will vary in relation to the polar/non-polar nature of both the gel and the solute.

27 Southall 1990, Wolbers 1990A, Burnstock and White 1990.

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painting. This would encourage increased penetration of moisture commonly

present in an uncontrolled atmosphere, which in turn could effect the movement of

soluble salts and other water-related damage mechanisms in a way that would

clearly be detrimental to the painting as a whole. The possibility in the long term of

damaging interaction between any residual surfactant and the materials of the wall

painting is an area that is as yet unclear and requires further investigation. It is

therefore of the utmost importance that if surfactants are used as part of a cleaning

system, they are completely removed afterwards.

4.1.4 Clearance.

As the solvents are volatile they do not present a direct clearance problem, however

the two non-volatile components, the Carbopol and the Ethomeen C-12, are the

materials that must be considered. Ethomeen C-12 is virtually insoluble in water,

however it can be dissolved in aromatic solvents. This is also true of most of the

Carbopol which will have been converted by the amine to a salt. There is a

possibility that some of the Carbopol may not have reacted to form a salt and in this

form will be insoluble in aromatics but readily water-soluble. Although this would

represent only a tiny proportion of the overall volume of the Carbopol, it is

necessary to deal with it at this stage, because once it has been allowed to dry, it

becomes far more difficult to redissolve.28

Clearance is further complicated be the physical nature of the surface of many wall

paintings. As well as the porosity associated with medium-thin secco or buon fresco

technique there are the complications caused by the very uneven surfaces commonly

encountered on wall paintings. The particular hazard associated with the clearance

of solvent gels is the tendency of the deep interstices to retain relatively large

28 Pers.comm. G.Stead. The reason for this is not a change in the chemical structure of theCarbopol, but rather the physical structure that occurs when it dries and reforms into larger lumps.

This reduces the ability of the water to gain the surface contact with the individual grains required

for the quick dissolution.

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amounts of the gel.

The clearance procedure must therefore involve both aqueous and aromatic

solvents. In order to avoid increasing the risk to soluble components of the painting,

the aromatic solvent used should the same that contained in the gel. The same

caution exercised when applying the gels should be continued here as the solvency

parameters of other soluble materials of the painting may coincide with those of the

material removed by the gel. This should be followed by aqueous clearance which

requires further caution. The gel itself contains very low concentrations of water, so

it is possible to use it with minimal risk over a water-sensitive surface that may be

put at risk by this stage of the clearing. Both clearance solvents are applied using

cotton wool swabs, in order to absorb the dissolved residues.

4.1.5 Possible drawbacks with Carbopol

A possible disadvantage with the use of Carbopol as the gelling medium is its

tendency to react with certain of the materials commonly found in wall paintings.

The polyacrylic acid produces COO" ions which can complex certain bivalent and

trivalent ions such as calcium and magnesium. Such a reaction would be of serious

concern in the field of wall painting conservation due to the presence of large

amounts of both these ions either as part of the original material or in the form of

soluble salts. Once this reaction has taken place the Carbopol becomes insoluble in

water and could present a serious clearance problem. It is possible that once the

Carbopol is formed into an amine salt during gelling, less reactive sites will be

available for the complexing to occur, thus reducing the possibility of a reaction. No

hard data is available on the exact nature of these reactions, however certain

empirical tests have been carried out which indicate that in its unneutralised state

the Carbopol reacts swiftly with the metal ions to become insoluble.29

29 Pers. comm. G.Stead. 14.3.91. Empirical tests were carried out with Carbopol and cement in

order to test the complexing of ions present in the mixture. Dry Carbopol was added to dry cement

which was then mixed with water. At first the result was viscous, but in a matter of minutes it

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42 Pemulen™

Pemulen, a product of B.F.Goodrich, is described by the manufacturers as a

^polymeric emulsifier'. It consists of a polyacrylic acid backbone similar to Carbopol,

copolymerised with fatty comonomers (the nature of which is proprietary

information). The polyacrylic acid part of the molecule is hydrophilic while the

comonomer is lipophilic resulting in a molecule with amphipathic or surfactant

properties. The effect of this is that the molecule is soluble in both polar and non-

polar solvents and is able to act both as a thickening and emulsifying agent.

4.2.1 Thickening mechanism of Pemulen.

The method recommended by the manufacturers of thickening a solution with

Pemulen (pH 2.5-3.0 at 1% in H2O) is by neutralisation using a base such as sodium

hydroxide. It would also be possible to thicken an aqueous solution by adding

Pemulen directly to it, however without neutralisation, the solution would remain

strongly acidic.

4.2.2 Drawbacks of Pemulen.

As with Carbopol, the polyacrylic acid will produce COO- ions able to complex

bivalent and trivalent ions such as calcium or magnesium.30 The copolymer is

considered to be very stable and this reaction would not cause it to break up,

however the reaction does cause the molecule, like Carbopol, to become

thinned to a liquid. This was thought to be due to the Carbopol chelating the calcium ions of the

lime in the cement and thus becoming insoluble in the water and thus inactive. A second

experiment was carried out neutralising Carbopol with sodium hydroxide in order to fill all the

reaction sites and inhibit the reaction with the calcium ions. This was then mixed with the cement

that had already been mixed with water. The result was a stable viscous mixture which did not break

down, suggesting that in its salt form the sites on the Carbopol were not free to complex other ions.

30 It is possible that the occurrence of complexing would be reduced by the process of neutralisationin much the same way as was proposed for Carbopol.

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insoluble.31 Apart from the obvious undesirability of leaving foreign materials on

the wall painting there is the possibility of further complications caused by the

amphipathic properties of the molecule, (discussed in section 4.1.4 on clearance),

resulting in ionic bonding of the surfactant molecule to the painting.

4.3 Cellulose Materials

Cellulose gelling agents such as carboxymethyl cellulose or hydroxypropylmethyl

cellulose have commonly been used as thickening agents in certain areas of

conservation.32 The principle by which they work is one of bulking out the system

into which they are introduced. When in aqueous solution the tightly packed long

cellulose chains are swollen by hydrogen bonding of the water. The gelling efficiency

is relatively low in terms of percentage weight to viscosity, and the amount needed

to achieve the degree of gelling required for this work would be extremely high

compared to a system based on a swelling material such as a polyacrylic acid

polymer. A further problem with the use of cellulose gelling agents on wall paintings

is one of clearance. Carboxymethyl cellulose is hygroscopic with an equilibrium

moisture content of approximately 18% at 60% R.H.33 Were some of the material

to become trapped in the porous substrate, it would provide nutrition for the

microbiological growth common in an uncontrolled environment. It is also known to

contract on drying which could present the danger of flaking of the paint layer.

5. Desiderata for Test Sites.

It was decided that the majority of the tests would be carried out on actual paintings

as opposed to specially prepared models. The main problem with such models is

that of aging and reproduction of the widely ranging contaminants. The alteration of

31 pers.comm., Mr C.Drake 21.2.91.32 CMC is used as the gelling agent for AB 57 and HPMC in Wolbers resin soaps and enzyme

cleaning systems. Wolbers 1990B. pp.148.

33 Hone 1987, pp.129.

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the solubility of aged materials is well documented for easel paintings,34 however

little or no work has been carried out in the field of wall paintings. The physical

problems of the solubility of aged polymers would almost certainly be complicated

by the intimate contact with the dense crystalline matrix encountered with a porous

wall painting. To simulate such a situation on a model would be extremely difficult.

The major disadvantage encountered carrying out the tests on actual paintings is the

reduced level of chemical control that can be exercised due to the complex nature of

the painting itself. The interaction of materials on a wall painting that has

undergone restoration is difficult to understand without a full knowledge of the

constituent parts of both painting and previous treatment. For this study sufficient

knowledge of the present state of these materials was needed to clearly define the

effects of the gel tests. To overcome this problem it was necessary to carry out

detailed analysis of the paintings in their present state, before any tests were begun.

The choice of paintings was intended to encompass a sufficiently wide range of

dates, techniques, and previous restoration treatments in order that the project

should give a representative view of how the gels perform in a range of different

situations. The decision to carry out the tests on a number of such sites introduced

an additional series of variables, such as state of conservation and interaction

between multiple previous treatments, that should be considered when examining

the results of each individual series of tests.

The three sites chosen ranged in date from the 12th to the early 15th centuries and

varied in painting technique with both organic and inorganic media.

34 Mills and White, 1987.

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6. Test Methodology and Procedure*

The intention of using the solvent gels was to dissolve a single specific layer of

material on the painting. In order that the components of the gel were tailored to

this layer it was necessary to have a certain knowledge of the nature of the

particular material to be dissolved.

6.1 Examination and Analysis

Initial examination of the surface coating was carried out on site under low

magnification using normal and ultra violet illumination. Under UV by examining

the colour and intensity of the fluorescence, it was possible to distinguish in detail

the variations in nature and thickness of the coating. Such information was

important in establishing where samples were to be taken, and in identifying any

anomalies that might occur during the examination of particular samples.

Two types of samples were taken. Cross-sections of the painting were taken for

examination with optical microscopy, scanning electron microscopy (SEM) and

energy dispersive X-ray analysis (EDX).35 Samples of the individual surface coatings

and samples of pure materials to act as controls36 were taken for analysis by Fourier

transform infrared reflectography (FTIR)37 and Thermomicroscopy.38

In order to establish the solubility parameters of the surface coatings, standard

solvent tests were carried out using free solvents. This established broadly, the types

of gels that should be tested on each site.

35 Cambridge Stereoscan 200.36 Spectra were obtained from Ethomeen C-12, Carbopol 934 and 940, and BDH bleached beeswax.

37 Tests were carried out on a Perkin Elmer 1710 FTIR.

All FTIR analysis for this study was carried out in the Diffuse Reflectance Mode.38 Analysis was carried out on a Mettler FP800 hot stage, and samples were examined at a

magnification of xlOO.

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6.2 Preparation of Carbopol Gels.

To prepare the gels used in the tests the first stage was to calculate the solvency

parameters required to dissolve the coating. In order to do this a Teas chart was

prepared with the solvency parameters of both the major solvents and the solutes

plotted over each other.39 The overall solvency parameters of each solvent mixture

was then plotted, giving a clear visual representation of the areas in which the work

was to take place, allowing fine tuning of particular gels to be undertaken with

greater ease.

The two main criteria for the gels are the viscosity and the solvency parameters of

the solvent mixture. A neutralising amine should be chosen that forms a salt with

the Carbopol that is soluble in a solvent with the required solubility parameters.

Certain further solvents can be added at a later stage in order to adjust the overall

solvency parameters of the gel. The order in which the materials are combined was

established through a series of empirical tests and is an important to achieve a

successful gel.

1. principal solvent.

2. Carbopol.

3. Amine.

4. Polar solvent.

5. Secondary solvents.

During the whole process there should be constant agitation of the mixture to

ensure that the individual materials are sufficiently dispersed throughout the system.

First the Carbopol is evenly dispersed in the principal solvent. Then the amine is

added to form the salt necessary for the uncoiling of the Carbopol. Initial gelling

occurs at this stage. Since sufficient viscosity is an important property of the cleaning

agent extensive testing was undertaken to examine how the degree of viscosity could

be enhanced. Increasing the amount of Carbopol had little effect apart from bulking

39 The nature of the solutes had first been determined by analytical means. (See below under 6.2).

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out the solution. However the addition of small quantities of a polar solvent was

particularly effective. Therefore on the basis of empirical observation the procedure

was modified to include the addition of a polar solvent (normally water) at this

stage. This produced a suitably viscous gel to which could be added the secondary

solvents necessary to achieve the correct solvency parameters.

The addition of the secondary solvents after the initial gelling had occurred was

found to be of utmost importance. If the secondary solvents were mixed with the

principal solvent before the addition of the Carbopol it was observed that the gelling

process often failed to occur. This appeared to be due to the fact that the salt

formed by the Carbopol and the amine has been specificly chosen for its solubility in

the principal solvent. The addition of the secondary solvent at this point may have

altered the solubility parameters of the mixture so that the dissolution of the

Carbopol would be partially or totally inhibited.

The following materials were examined for their suitability as gelling agents for non-

polar solvent systems, but were considered to be less suitable than Carbopol.

6.3 Test Procedure

The procedure for the gel test was the same at each site. The gel was applied by

cotton wool swab and left static on the surface for a recorded period of time. After

this it was gently moved around with the swab in order both to remove swollen

material from the gel/surface interface and to move fresh gel into contact with the

surface. At the end of this period the gel was removed with a dry swab and the area

of the test was thoroughly swabbed with the aromatic solvent base of the gel (white

spirit or xylene) in order to clear any residues of the gel. Finally the area was

swabbed with deionised water to remove any remaining residues. The area was

allowed to dry before further samples were taken in order to asses the level and

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effect of cleaning. In some cases an intervention layer of Japanese tissue was used

during the tests. This was removed before clearance was carried out. The result of

each test was used to determine which gel was used for the following tests.40

6.4 Clearance Tests

Analysis to establish whether the clearance procedure was successful in removing all

residues of the gels was carried out in two stages. Initially all samples taken after

clearance were examined with normal light and UV microscopy and SEM to see if

any deposits of residue could be identified. In order to undertake more detailed

tests it was considered most expedient to use a model rather than carry out the tests

on actual paintings. This was necessary primarily due to the relatively large size and

controlled nature of the sample required. It was expected that if a residue was

present, its volume would be extremely limited compared to the that of the overall

sample and FTIR analysis would be further complicated by the interference of high

background 'noise' from the inorganic material from the surface of the painting that

would make up the major component of the sample. To take samples of the

necessary size from actual paintings would be nether justified or practical.

40 Appendices 1 & 5.

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7.0 St. Marv and All Saints Church. Holcot.41

7.1 Introduction

There are a number of different painting schemes in the church, all of which were

coated with wax, possibly by E.W.Tristram42 who describes them in his 14th-century

volume.43 The area selected for the tests was part of the immense area of painting

(54 x 12ft) on the north wall of the north aisle said by Tristram to depict 'six

Apostles, one probably StJohn, bearing the cup, and another St.Bartholomew with

the knife;'.44 Although the paint layer is flaking in certain areas, apparently due to

the activity of soluble salts, a suitably sound and accessible area was found on the

lower part of the painting. The painting is simple and linear in style, and probably

dates from the early 14th-century.45 It is very medium thin but probably painted

with a combination of organic and lime media.46

7.2 Painting Condition

Initial examination of the painting on the North wall showed that the surface was

coated with a relatively thick homogeneous layer of a translucent waxy material.

This was covered with a large amount of what appeared to be surface dirt. UV

examination showed that the coating had a weak fluorescence, and losses due to

damage showed clearly. The condition of the paint layer varied considerably, with

some areas suffering severe flaking and loss. Much of this damage appeared to be

due to the decohesion of the upper part of the substrate causing the surface layer to

break up. This may well have been due to the movement and crystallisation of the

soluble salts within the wall rather than on the surface, due to the impermeable wax

coating. However, much of the painting was sound, and it was in such an area that

41 Appendix 8.42 The beeswax-based material found on the wall is consistent with Tristram's recipe of c.1926.

Appendix 1.

43 Tristram 1955, p.181

44 Ibid.45 Ibid.46 See section 7.3

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the tests were carried out.

7.3 Cross-Section Analysis and SEM.

The thickness of the coating varied in some areas, but it appeared that there was

only a single coating present. In cross-section under both UV and normal

illumination this appeared to be the case (PI. 1). On top of this coating there

appeared to be a thin layer of crystaline material, which was discrete from the

coating and did not penetrate it. Under SEM this material could be seen on the

surface of the sample over the soft coating that covered the paint layer in a thick

unbroken layer (PL 12). At a higher magnification of xl380 the material appears to

be some form of effluorescence over the surface of the coating (PI. 13). It was

however easily removed with a soft sable brush, suggesting that it may simply be an

unusually thick layer of ambient dirt that had settled on the soft surface coating.

In cross-section, the structure of the painting can be seen to be relatively simple.

Above the plaster (not shown in the cross-sections) are two layers of tinted

limewash of varying thickness. In areas of background the limewash would have

formed the original paint surface over a lime ground. In figurative areas there is a

pigment layer over a single limewash ground. Media stains were carried out on a

number of samples, but the only positive result was achieved with Acid Fuchsin

which weakly stained the upper part of the limewash and pigment.47 This suggests

that for the limewash ground a small amount of protein was used as an additional

binder in what is mainly a calcium carbonate matrix. This relatively porous matrix

can be seen in SEM under relatively low magnification on the lower left hand side

of PL 12. The paint layer is very fine with a dense pigment content, and

identification of media by staining did not prove conclusive, however it appears

possible from the other analysis that an proteinous binder was used.

47 Acid Fuchin 2% vol/vol in deionised water. Rinsed with deionised water.

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7.4 FTIR and Thermomicroscopv

Samples of the coating were taken for organic analysis from two areas on the edge

of a large loss, where there was enough depth to avoid contaminating the sample

with large amounts of inorganic material from the surface of the painting. With

FTIR both samples produced similar spectra,48 showing that the majority of the

sample consisted of beeswax.49 This interpretation appeared to be confirmed by the

results of Thermomicroscopy which showed that the coating had a melting point of

approximately 64°C.

7.5 Solvency Parameter Tests

The free solvent tests carried out showed that the coating was readily soluble in a

range of aromatic and aliphatic hydrocarbons. A large part of the surface coating

was removed using xylene, without any apparent damage to the paint surface below

which appeared to be insoluble in the solvents.

7.6 Solvent Gel Tests

Solvent gel tests showed that the most effective cleaning action was achieved with

gel 7.50 Clearance was carried out with xylene and water. The optimum application

time was 20 seconds stationary on the surface followed by 60 seconds agitation with

a swab.51 SEM analysis of sample HO9/567 taken from this area show that the gel

had achieved a considerable level of thinning to a consistent level over the surface

of the sample (Pis. 14 & 15). This shows that there is still a fine film of the wax over

the paint surface, but that it is so thin that the material on the paint surface is

breaking through. PL 16 also clearly shows the limited level of penetration of the

wax coating and it would appear that a longer application of the gel would be

48 Appendix 5.49 persxomm. M.Odlyha and R.White.

50Apendix3.51 Appendix 8.

-31-

necessary to achieve complete removal.

Tests with gel 7 were also carried out through an intervention layer of fine Japanese

tissue for a period of 70 seconds. The effect of this was to considerably reduce the

amount of mechanical action on the surface of the paint film. During the period of

application less of the coating material was removed from the surface than without

the intervention layer, the majority of the cleaning action occurring when the tissue

was removed and the area swabbed with xylene. This appeared to lift off the heavily

swollen organic coating, with very little mechanical action necessary. Two

applications of the gel were necessary over an intervention layer to obtain the same

level of cleaning as a single direct application. The level of mechanical action on the

surface was however considerably reduced. This appeared to be confirmed by SEM

which shows a similar level of cleaning to that seen in Pis. 14 & 15. The SEM also

suggested that there were no significant residues of the gels present on the samples.

The wax coating was readily soluble in aromatic solvents in either a gelled or free

state and the best level of cleaning achieved by the gels in these tests was slightly

greater than that achieved with free solvents. The advantages of using a gel was the

dramatic reduction in mechanical action necessary to achieve the results and the

homogenious nature of the removal of the wax coating. The area on which the tests

were carried out was relatively sound, however much of the painting is in a far less

stable condition, and such a reduction would minimise the risk of damage to the

paint surface during cleaning.

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8. Holv Sepulchre Chapel. Winchester Cathedral,

8.1 Introduction

The earliest of the three sites is the Holy Sepulchre Chapel in Winchester

Cathedral. This contains two schemes of painting, the earlier of which dates from

between 1175 and 1185 and the later, from c.1220.52 Until the 1960s the only visible

part of the 12th-century painting was that situated on the south wall of the west bay,

depicting the Resurrection of the Dead. The main area of the earlier scheme,

situated on the east wall, was revealed in 1963 during work carried out by Mrs. Eve

Baker and her assistants. The 13th-century scheme, depicting the Entombment and

the Resurrection of Christ, was detached to reveal the very fine earlier painting of

the same subject.53 The newly revealed areas of 12th-century painting survived in

remarkably good condition, despite the heavy keying marks inflicted when they were

covered by replastering for the 13th-century scheme.

8.2 Technique

While the 13th-century paintings have always been assumed to be in a secco

medium, the appearance of the 12th-century paintings has suggested that they are in

fresco technique.54 The discovery under the 13th-century painting on the south wall

of the east bay of part of a 12th-century sinopia overlayed with a small area of

painted intonaco depicting the head of a male figure, suggested that the technique

was very similar to the Italian buon fresco technique, as described by Cennino

Cennini in his Libro dePArte. Recently, analysis undertaken on areas of the painting

on the east wall has shown that the technique is more complex than has so far been

assumed. Pigments not commonly associated with the boun fresco technique such as

red lead and vermilion were identified, suggesting a combination of both organic

and inorganic media.55

52 Park 1983, pp.53 & 4853 Ibid., pp.3854 Park 1983 pp.40

-33-

The technique on the west bay of the south wall appears to be somewhat different.

Analysis of sample HS6/530 taken from the black outline of one of the angels flying

down to take up a resurrected soul again showed a thin layer of coating with small

wax residues on the surface; more importantly however it showed that this area of

painting is not in the same technique as the area in the east wall. Deep losses on the

painting reveal that there is only a single layer of plaster in this area. On this is a

layer of limewash on which is painted the under-drawing in a red pigment. Over this

is not an intonaco, but a second layer of limewash over which is painted the final

outline of the figure in carbon black apparently with a lime binder (PI .6). Further

examination of the painting confirms that this is the case, as in areas where the paint

surface is lost the red underpaint is clearly visible under a limewash and not an

intonaco.

8.3. Conservation History

The early restoration history of the paintings is undocumented, however it appears

from analysis carried out in the course of this project, that all the areas of painting

visible before the most of restoration in the 1960s were treated with one or in many

cases two layers of organic 'preservative' coatings. E.W.Tristram is thought to have

worked on the paintings which are documented in his volume on the 13th-century56

published in 1950 and it can be assumed that it was he who applied the upper (wax)

coating over a previous varnish layer, however the exact date of its application is

unknown. In 1959 The Eve Baker Trust began a program of restoration that

continued until 1970.57 It was during this period that the 13th-century paintings on

the east wall were detached to reveal the very fine 12th-century paintings below.

During this period also, work was carried out on the 12th-century scene of the

55 Hluvko 1991.

56 Tristram 1950

57 Baker 1964,1967,1970.

-34-

Resurrection of the Dead on the south wall of the west bay. A certain amount of

cleaning took place on the coated areas, probably with Nitromors or a homemade

mixture based on this formulation58, and an area of 13th century painting on the

right hand side of was removed to uncover a well preserved figure of a trumpeting

angel of the earlier scheme.59

The 12th-century scene of the Resurrection of the Dead (with the exception of the

recently uncovered angel) is therefore unique in the chapel in terms of conservation.

It is the only area of the 12th-century painting to be exposed at the time of the early

restorations, and so it is the only area of predominantly lime bound painting to have

been coated with organic preservatives. This area of the painting was therefore

selected as a suitable site to carry out the solvent gel tests.


The initial examination of the area of 12th-century painting to be tested in the Holy

Sepulchre Chapel showed that it was unusually dark for a wall painting treated only

with a wax-based material. Under low magnification a thin layer of coating could be

seen, the surface of which was covered with a number of residues as well as normal

surface dirt. One of these residues, which appeared to have been left in circular

patterns consistent with wiping action, was distinct from the surface, with a white

papery texture and a bright whitish fluorescence under UV illumination.

Examination of the rest of the area under UV illumination showed that the organic

coating, although very thin, was fairly homogeneous being broken in a few areas by

later damage. The only exception to this was in deep interstices or small losses,

58 Pers. comm,, David Perry.59 This area had previously been ignored by past restorers as it had been covered by a spiralstaircase inserted at the request of Samuel Wesley during his time as organist at the Cathedral(1849-1865), to enable him to reach the organ loft more easily. The staircase was removed andbroken up in 1938, pers. comm. John Hardacre. This revealed a badly damaged area of 13th-centurypainting that was detached in the 1960s restoration by the Eve Baker Trust, to reveal the 12th-century angel, pers.comm. David Perry.

-35-

where the coating was thicker. Here it fluoresced slightly differently to other areas

with a weak greeny/yellow tint. Samples were taken from these areas for analysis as

they were the only areas with sufficient material available for FTTR analysis. The

condition of the paint surface below the coating is varied. In some areas there is

considerable flaking, some of which appears to be relatively old, but some is more

recent, suggesting that the damage in this case is active. There are also widespread

losses of the paint surface, revealing the red under-drawing below, however the

majority of these appear to have occurred before the application of the surface

coating.


Visible light microscopy clearly showed a fine translucent layer of material over the

surface of the painting (Pis. 3 & 5). Under UV illumination this layer had little or no

fluorescence, however in this light source it was possible to see isolated areas of a

second fine layer on the surface which fluoresced differently, being slightly brighter.

This layer was very fine and broken and was just discernible in visible light at a

magnification of x400. With SEM this material can be seen on the surface of sample

HS5/529 as a disrupted residue incorporation surface dirt that obscures the crazed

surface of the more homogeneous coating below (Pis. 17 & 19). The SEM clearly

illustrates the way in which the lower organic coating penetrates the porous matrix

of the lime-bound pigment (PL 18).

8.6 FT1R and Thermomicroscopy

The FITR spectra of the samples of the surface coating obtained from the

interstices showed that the majority of the material in the samples was beeswax,60

contaminated with large amounts of inorganic material, possibly from the paint

layer. No further organic material was apparent.61 These results were further

60 Appendix 5.

61 Pers. comm. M.Odlyha and R.White.

-36-

supported by Thermomicroscopy which showed that the coating had a melting point

of approximately 64°C. These results in combination with those described in 8.5

suggest that the material analysed here was not the coating now generally visible on

the paint surface, but the remains of a second more recent coating. It appeared

therefore that until the 1960s there had been two layers of organic coating on the

paint surface,62 and that the upper one of these, the beeswax, had been partially

removed at this time leaving the thin wax residue on the surface of the earlier hard

coating, but remaining in quantity in interstices or damages. This may also explain

the presence of the other Vhite papery' material found on the surface which may

well be the residue of the cleaning agent used at that time. FTIR analysis carried

out on a sample of this material, indicated that it was possibly some form of

cellulose.63 This was also suggested by Thermomicroscopy which showed the

material charring at approximately 250°C.

8.7 Solvency Parameter Tests

A range of solvent tests was carried out to establish the solvency parameters of the

coating, however the results were limited. Strongest solvency was in the region of

the aromatics, but it was observed that after an initial removal of a small amount of

material (probably beeswax) no further action took place.

8.8 Solvent Gel Tests

The results of the gel tests appeared to confirm the observations made with visual

62 David Perry, of the Perry Lithgow Partnership, and former conservator with the Eve Baker Trust,confirmed that this is probably the case. He carried out much of the work in the chapel during the1960's program, and said that he came across a second coating under the wax that was impossible to

remove in certain areas. He felt that it may have been a resin varnish.63 It was thought possible that the material was a residue of the cellulose part of the gelling mediumof the paint remover Nitromors (Celacol MMPR1) that may have been used as a cleaning agent inthe 1960s intervention. Celacol MMPR1 was produced by Courtaulds Ltd. It is however no longerin production and an infra red spectra of the material was not available. The material producedtoday considered to be the closest chemically to Celacol MMPR1 is Celacol HPMMPR1, anhydroxypropyl methyl cellulose (pers.comm. Dr.N.G.Todd). IR spectra of this material, comparedone from the Winchester sample (KMHS2) showed similarities in diagnostic frequencies,

suggesting that it was a similar cellulose material. Appendix 5.

-37-

examination and analysis. The optimum effect was obtained with gel 7 applied for

10 seconds static and moved for a further 60 seconds.64 Clearance was then carried

out with xylene and water. The cleaning was very limited and similar in effect to that

achieved by the aromatic free solvents applied in the tests to establish solvency

parameters. A small amount of material including dirt and residues of the upper

wax layer on the surface of the coating were removed, but the lower resin coating

appeared to remain unaffected.

Analysis of sample HS7/571 taken from the area of this test would appear to

confirm that the residues of the wax layer had been removed leaving the lower layer

untouched. In cross-section at magnification up to x400 the lower layer was clearly

visible over the pigment surface (PL 4), and under UV the remains of the upper

layer were no longer visible. This was further shown by the SEM examination of the

surface of the sample (Pis. 20 & 21). Comparing this to the surface of sample

HS5/529 before cleaning (PL 19), it is apparent that the disrupted material on the

surface has been completely removed, while the lower layer remains in tact.

Clearly the gel is working efficiently and thoroughly on the material for which it was

designed. The earlier resinous layer should be further analysed in order to establish

its exact nature, and a second cleaning system should be designed to remove it.

64 Appendix 2.

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9. Westminster Abbev Chapter House.

9.1 Introduction

The Chapter House of Westminster Abbey has a complex history and the survival of

the paintings on its walls is remarkable considering the number and scope of

interventions that have occurred. The paintings, depicting scenes from the

Apocalypse of St. John were probably carried out sometime between 1372 and 1404,

and are of the highest quality.65 Each side of the octagonal Chapter House, except

for the west entrance wall, contains five bays separated by Purbeck marble

arcades.66 The condition of the individual areas of painting varies according to that

of the ashlar masonry support, and the type of previous restoration. The only

internal wall is the north west (side 1), and here not surprisingly, the paintings

survive in the best condition.

The Chapter house was built by Henry III from c.1245-1255, and was apparently

intended from the outset to serve an additional function as a secular meeting room.

The Great Council met there in 1257, and it was a frequent venue for parliament

until 1547. From the dissolution it served as a store for public records, and the

provision of a gallery and book-shelves against the walls caused a certain amount of

damage to the architecture. The first restoration was carried out by George Gilbert

Scott from 1866-73.

92 Technique

The painting are carried out on a white ground directly over a substrate of tooled

closely jointed ashlar masonry the shows through paint layer. The paint layer itself is

complex with a number of different pigment layers and surface glazes,67 with

pigments of the highest quality.68 It would appear likely that there would have been

65 Turner 198566 Numbering of the 7 sides is carried out clockwise from the entrance.

67 Hluvko 1991.

-39-

an original varnish, however this is no longer visible.

9.3 Conservation History

The conservation history of the paintings, although better documented than in most

cases, is complex and unspecific in the location of particular treatments.

9.3.1 G. G. Scott

The first recorded treatment to the paintings was probably carried out under Scott.

The exact date and method is not recorded, however references to the paintings in

his book of 1863 throw some light on the subject.69 Scott refers to his discovery of

the paintings behind the bookcases that had obscured them and agrees with

Eastlake that they date from the mid 14th-century and with his suggestion that the

medium is oil.70 Although Scott does not refer to treatment of the paintings, he does

describe the treatment of the stone tympanum over the entrance. This was first

cleaned with a soft jet of air, and then injected with an (unspecified) solution, the

effect of which was to harden the decayed stone. It is possible that a similar

treatment might have been used on areas of painting where the stone support was in

the same condition as the tympanum. The only direct reference to Scott's treatment

of the paintings is by Prof. A. H. Church who in his report of 1904 refers to the

difficulties he had treating the paintings in the North West arcade, which he said

that Scott had varnished.71

9.3.2 Prof. A. H. Church

Church himself carried out work on the paintings between 1901 and 1903. In his

report of 1904 he claims that the damage to the paintings was due mostly to the

68 Hluvko 1991 and Howard 1988.69 Scott 1863, pp. 40-43

70 Eastlake 1947. pp.571 Church 1904

-40-

attack on the stone by the 'acidic atmosphere', which not only broke down the weak

structure of the stone, but introduced further soluble salts to the paintings. In his

analysis Church discovered that as well as chlorides, the stone contained large

quantities of sulfates, the source of which he thought to be atmospheric sulfur

dioxide. This had reacted with the calcium carbonate in the wall to form larger and

water-soluble calcium sulfate crystals, causing the breakdown of the cohesion of the

stone, resulting in the damage to the paintings. To counter this Church treated the

paintings with baryta water applied six to twelve times in order to introduce enough

barium hydroxide into the wall for the treatment to prove effective.72 This in turn

introduced a large amount of water into the wall which Church had himself

acknowledged was causing damage due to the mobilisation of soluble salts.

9.3.3 H.M.Office of Works

The third treatment took place in 1929 and is recorded in an anonymous article in

the Museums Journal of that year which mentions that in many of the bays there

was a severe deterioration of the stone and that the paintings had a uniformly gray

appearance.73 This could have been due to the barium carbonate bloom which

Church himself acknowledged as a possible consequence of the 1901-03 baryta

water treatment.74 To fix, consolidate, and restore the aesthetic quality of the

paintings, a coating of bleached beeswax dissolved in turpentine with 2% linseed oil

was applied to the paintings.75 Flaking paint was readheared by injecting this

solution behind the paint layer with a syringe and pressing the flakes back by hand.

Consolidation of friable areas was carried out by spraying the solution onto the

72 Baryta water is an aqueous solution of barium hydroxide. The theory behind the treatment was

that calcium sulfate crystals would be converted into the more stable and insoluble barium sulfatecrystals. This would leave calcium hydroxide which would reconvert to calcium carbonate with

atmospheric carbon dioxide.1. CaSO4 + Ba(OH)2 -> Ca(OH)2 + BaSO4

2. Ca(OH)2 + CO2 -> CaCO3 + H2O

73 H.M.Office of Works. 1929, pp.376

74 Church 1904. pp.575 The same mixture without the turpentine was applied in some areas with the use of heat

administered by a baffled blow torch.

-41-

surface and then encouraging its penetration with the use of a paraffin blow torch

fitted with a baffle.76

9.3.4 English Heritage

The most recent treatment was carried out in 1985 by English Heritage, when the

paintings on the north west side were cleaned and the coating (there was only a

single wax coating on these paintings) removed with a mixture of 80% White Spirit

and 20% Propan-2-ol. At at the same time a partial cleaning was carried out on all

the other paintings in the Chapter House. This was undertaken using a hot-air

blower to melt the wax on the surface, which was then removed with large cotton

wool swabs.77


The initial examination showed that the surface was very uneven and broken in

some places and that areas of the paint surface were seriously disrupted, apparently

due to the damaged stone support. There were areas where serious flaking had

occurred in the past, but all of these had been coated and consolidated with the

waxy coating. The overall condition of the painting was therefore sound in that no

active damage was occurring, however the true state of the painting below the

coating was far less solid. It was clear that more than one coating was present, but

the exact limits of each layer was difficult to establish. Under UV it could be seen

that there were two dominant coatings. The upper one appeared to be a soft waxy

material, and was very thin in some areas. Towards the edge of the painting where it

was protected from the 1985 partial cleaning by the pillars this coating is far thicker,

up to lmm in some areas, suggesting that the majority of the material had been

76 During the process a certain amount of the old varnish was removed. This was usually carried outwith a mixture of methelated spirits, benzene or turpentine, however where the material proved

particularly hard to remove, pyridine (C5H5N) was used. H.M.Office of Works 1929. pp.376.

77 Pers. comm. J. Keevil, Head of the English Heritage conservation studio.

-42-

removed in the 1985 treatment. Beneath this layer was a second coating, consisting

of a thick layer of a hard dark resinous material. Both layers were heavily

contaminated with paniculate material, apparently a combination of ambient dirt

and material from the paint surface.


Samples were taken in most cases from sections of white pigment on and around the

scroll in the center of the area in an attempt to obtain similar layer structure to

facilitate comparison in the cross-sectional analysis. In practice this failed to occur

due to the severe damage and the complex nature of the painting which was further

confused by the effects of earlier restorations. It was clear from all the samples that

there were two separate surface coatings as had been expected. The upper coating

was very fine in some areas, and had very little autofluorescence under UV

microscopy. Under SEM this layer had a soft feathery appearance characteristic of

wax (PL 24),78 and although thin was fairly homogeneous over the paint surface.

The lower layer fluoresced with a yellow/green tinge under UV and was relatively

thick. Under SEM it was possible to see the hard fractured edges typical of a natural

resin varnish. The interface with the paint surface was very disrupted with what

appeared to be material, possibly salts, effluorescing through the paint surface itself

(PL 7).

9.5.1 Binding Media

The structure of the painting itself was immensely complex with up to six often

discontinuous layers present in the same sample. On a number of the samples taken

from the edges of more prominent losses, the lowest layer (above the stone

substrate) consisted of the same wax material to be found on the surface. This

showed how the wax had been used as both fixative and consolident, and was

injected behind such loose edges in order to readhere them as explained in the 1929

78 pers. comm. Aviva Burnstock.

-43-

report and is apparent in PI. 10.

The nature of the medium of the painting is of obvious importance when

establishing the solvency parameters of the gels. Past analysis79 and the survival of

records regarding the purchase of large quantities of oil80 appeared to suggest that

the predominant medium was indeed oil. In order to confirm this, stain tests were

carried out with Sudan Black B,81 Acid Fuchsin,82 and the fluorochrome stain for

lipids, Rhodamine-B.83 The Sudan Black failed to stain the apparently medium-rich

pigmented layers, but took strongly to the thick lower layer of the coating. Acid

Fuchsin only stained in a single case when it took to two small isolated areas on the

lower side of the sample, suggesting that protein was not commonly present, and

that these two areas were anomalous. Under UV the Rhodamine-B was seen to

have stained the central pigment layer, which appeared to be the most medium rich,

a light purple indicating the possible presence of lipids. The stain was far too weak

in this area to suggest the presence of any large quantity of oil, but was stronger on

the bottom of the sample where an area of wax appeared to have penetrated behind

the paint surface (PL 9.).

9.6 FTIR and Thermomicroscopy

Samples taken of both surface coatings were examined with FTER and

Thermomicroscopy in order to further identify and differentiate between the two

layers.84 The resulting spectra had diagnostic frequencies clearly showing the

presence of beeswax in both samples,85 and neither contained any peaks that

79 Howard 198880 Eastlake 1847. pp.49-5581 Sudan Black, a saturated solution in IMS. Rinsed with IMS.

82 Acid Fuchsin 2% vol/vol solution in deionised water. Rinsed with water.

83 Rhodamine-B. 0.02% vol/vol solution in IMS. Rinsed with IMS.84 To enable a larger volume of sample to be gathered, they were taken from the edge of the

painting, where less of the upper layer had been removed in 1985.

85 Appendix 5.

-44-

indicated the presence of an organic resin. Thermomicroscopy showed that the

samples had a melting point of approximately 64°C, also indicating the presence of

beeswax. The conclusion to be drawn from these results is that the resin layer which

is clearly visible in SEM and visible microscopy failed to be collected in the sample.

Both samples were heavily contaminated with what appeared under low

magnification to be dirt, resulting in the high level of background noise on the

spectra.

0.7 Solvent Parameters Tests

The area of painting chosen for the gel tests was in the third (central) bay of side 6.

Although much of the painting in this bay is severely damaged, the area in the lower

right hand scene appeared to be reasonably well preserved beneath its coating of

dark wax and resin. A range of solvent tests showed that the upper coating was most

soluble in the aromatic region, with a mixture of xylene and benzyl alcohol in the

proportions 2:1 having the strongest effect. None of the tests appeared to have any

effect on the lower resin layer.

9.8 vSolvent Gel Tests

Due to the lack of solubility demonstrated by the resin layer in the earlier solvent

tests it was felt that tests with aromatic solvent gels could take place on the upper

wax layer without affecting the lower layer.

As with the Holcot and Winchester tests, the most successful cleaning was achieved

with gel 1J86 Applied for 105 seconds in all and cleared with xylene and water, this

successfully removed the upper wax layer while leaving the lower resin layer

apparently untouched. Using SEM this can be seen on sample WA8/558, leaving

the smooth resin surface and the pigment layers below (PL 25). In order to remove

the resin layer two resin soaps developed by the National Gallery Scientific

86 Appendix 2.

-45-

Department, and described in the 1990IIC Brussels conference,87 were tested on

areas already cleaned with gel 7. The 9-fluorenone-4-carboxylic acid soap (9FOC),

applied for 120 seconds, and cleared with xylene and water appeared to have little

or no effect on the material. The Anthracene-9-carboxylic acid soap (A9C), did

appear to have some cleaning effect. Also applied for 120 seconds, and cleared with

xylene and water, the effect was noticeable even at low magnification. Under SEM

the cleaning action is more apparent. The surface of WA14/564 (PL 26) shows that

the soap had significantly thinned the resin without disrupting the paint layer by

undercutting. Examination under UV illumination appeared to show a bluish

fluorescence in the area of the A9C test; none was seen in the area of the 9FOC

test. As the A9C is not known to be autofluorescent, it is possible that the apparent

fluorescence was due to the materials of the painting rather than those of the

cleaning reagent.

10. Analysis for residual materials

It was clear from both visible microscopy and SEM that at the three sites where tests

were undertaken that the majority of the gel was removed from the paint surface,

and that any residues that may remain would be relatively small. With the type of

organic analysis available, the size of sample necessary to obtain a volume of

residue that was identifiable would have to be relatively large. It would have been

impossible to take such samples from the surface of the test paintings, and so it was

necessary in this case to use a studio model. This had the added advantage that the

materials could be controlled, thus avoiding the contamination with unknown

materials that samples taken from actual paintings would be likely to have and that

could mask the results.


-46-

The model was a small block of approximately 3.5cm sq., constructed of two layers

of plaster, an arriccio with a large aggregate, and a thin lime-rich intonaco (pi. 11).

The surface was painted in buon fresco technique with yellow ocher. The block was

made and painted in 1988, and so the lime would have been well carbonated at the

time of the tests. Three weeks before the tests were carried out, half of the surface

of the block was treated with a wax-based mixture typical of the type used by

Tristram during the second quarter of this century.88 The day after application this

was polished with a dry cloth as was recommended.

Before the gel tests were carried out surface scrapings were taken from both the

waxed (KSR 1) and unwaxed surface (KSR 3). In both cases the sample area was

about lcm sq. The samples were intended to contain all components that might

contaminate a sample taken after testing, this included pigment, calcium carbonate,

surface dirt and in the case of KSR 1 the wax coating. Gel tests were carried out on

both areas with gel 7, as this had been the most successful gel on the site tests, and

cleared with xylene and water. Similar samples were then taken on the waxed (KSR

2) and unwaxed areas (KSR 4) after testing. In the latter case small amounts of wax

were removed from the interstices around the edge of the gel test area, as it was

important to establish whether residues were left in the coating itself.

FTIR analysis was then carried out on all four samples as well as on samples of

Carbopol 940 and Ethomeen C-12, the non-volatile components of the gel.89 None

of the diagnostic frequencies of the Carbopol or the Ethomeen could be seen on

either spectra obtained from the after cleaning samples (KSR 2 and KSR4) however

in some cases this could be due to masking by another peak. This result is

encouraging, but as it is in effect uncalibrated it does not mean that the residues are

definitely not present. It would be necessary to conduct a series of tests to obtain an

88 Appendix 1.89 Appendix 5.

-47-

internal standardisation for these results to show positively that the samples

contained no residue from the gel.90 Further analysis to establish the presence of

residues could be carried out using secondary ion mass spectroscopy which would

prove more sensitive for low concentrations than the FTIR.

11. Conclusions and Further Research.

It appears that the use of a gelling medium contains, and, in effect, enhances the

action of a particular solvent in terms of the amount of the solute dissolved over a

given period of time. This is apparently due to the gelling medium reducing the

speed of evaporation of the solvent thus allowing it a longer and more intimate

period of contact with the solute. The gel medium will therefore have a greater

effect enhancing the action of highly volatile solvents, than those with relatively low

rates of evaporation which would, in their free state, remain in contact with the

solute for a longer period of time.91 This enables one to use a relatively inefficient

solvent in a gel to perform the work of a 'stronger' free solvent. Therefore a

material only partially soluble in a certain solvent could more efficiently be

dissolved using the same solvent in a gel system. This reduces the risk to other

materials with similar solubility parameters to the desired solute that may be

effected by the use of a 'stronger' free solvent that may traditionally have been used

to remove the main solute. The results of this and earlier work demonstrate that it is

90 A series of tests could be carried out decreasing the volume of the gel in a standard sample untilit no longer registered on the FTIR. This would establish a base-line for the detection of residues

which could be related to the results obtained in the present tests.

91 To verify such an hypothesis a series of tests could be undertaken with two solvents of similar

solvency parameters but different rates of evaporation. Both solvents would be applied first in their

free state and then in a gel for a set period of time. The resulting dissolution of the solute could

then be measured for both tests in terms of how much material had been removed and the resultscompared to establish in terms of percentage gain ('gain' would be considered to be an increase inthe material removed from the solute), whether the highly volatile solvent had increased its effect

more that the low volatility solvent.

-48-

possible to produce a variety of gels with a wide range of solvents, both polar and

non-polar, allowing extreme flexibility and the adaptation a particular gel to deal

with a specific problem.

The health and safety implications are clear. The gels system by reducing the

evaporation of the solvents reduces the volume of solvent released into the air in

contact with the conservator. The choice presented by the wider range of solvents

available in a gel system able to dissolve the same material also allows the use of

less toxic solvents.

Empirical observations made during the gel tests at Holcot using an intervention

layer give a further important insight into the working method of the gels. It appears

that rather than completely dissolving the wax and absorbing it into the body of the

material, the gel is simply swelling it to a high degree, and the mechanical action of

the swab is removing the wax in its swollen state from the active interface between

gel and coating. It is clear then that mechanical action although significantly less

than that involved in traditional solvent cleaning is an integral part of the solvent gel

cleaning process, not only removing the swollen material from the surface, but also

replacing the gel at the interface with a fresh solvent-laden gel enabling the process

to continue. Surface characterisation of cleaned areas with SEM, suggests that the

action of the gels is one of thinning the coating from the surface down rather than

swelling and dissolution as might occur with the use of free solvents. The effect of

this is to allow far greater control to be exercised over the level of cleaning.

Although many of the results of this project are encouraging in regard to the use of

solvent gels for the cleaning of wall paintings, it must be regarded as part of a larger

long-term study. There are a number of areas which require further and more

detailed investigation. Most important among these is the clearance of the gels

discussed above in section 10. From SEM characterisation it is apparent that there

are no sizable residues of the cleaning reagent deposited on the surface of the

-49-

samples after clearance. However, it is necessary to establish by more specific

analysis, before the gels are used on any scale, that all the non-volatile material is

being removed. The analytical techniques most likely to identify the presence of

very small concentrations of the cleaning materials are gas chromatography with

mass spectrometry (GCMS).92

The effect of solvent gels on the paint layer is an area that has not been extensively

examined in the scope of this work, primeraly due to the nature of the particular

paintings tested. In two cases, there appeared to be no organic component in the

paint layer that would be effected by the gel, while in the third (Westminster Abbey)

the vulnerable paint layers were protected by the presence of the resin layer

beneath the wax that proved to be insoluble in the gels. Due to the nature of the

solvents contained in the gels, there is clearly a potential risk to certain organic

components that occur in many wall paintings. Further investigation should be

specifically aimed at examining such effects in order to establish more exactly the

action of the gels on such vulnerable materials.

A third area which requires further research is the effect that surfactants have on

the solubility parameters of certain solvents. The use of a surfactant allows a polar

solvent such as water to dissolve a non-polar material upon which, without the

surfactant, it would have no effect. It appears probable that this effect would occur

to a greater or lesser extent with all solvents combined with a surfactant. In theory

this could radically alter the accepted solvency parameters. As the gels discussed in

this project all contain a certain amount of material with surfactant properties, the

solvency parameters calculated in the standard manner may be affected in a way

that has not been predicted.

The use of solvent gels for removing wax coatings from wall painting clearly has


-50-

advantages over some of the 'traditional' methods. Most importantly it allows a far

greater control over the solvent parameters of the system, in effect making the

whole process more specific to the individual material to be removed thereby

reducing the risk to other soluble materials in the painting. The reduction in the rate

of evaporation of the solvents included in the gel is without doubt advantageous in

terms of health and safety to the conservator, as is the possibility of using less toxic

solvents in some cases. Further tests are necessary before these solvent gels can be

widely used, however the results to date show that they can be successfully employed

in certain cases.

-51-

12.0 BIBLIOGRAPHY

Baker, E. 1964, 'Wallpaintings in the Holy Sepulchre Chapel.', Winchester

Cathedral Record, pp. 10-12.

Baker, E. and Baker R. 1967, 'Paintings in the Chapel of the Holy Sepulchre.',

Winchester Cathedral Record, pp.21-25.

Baker, E. 1970, 'The Holy Sepulchre Chapel, Winchester Cathedral.', Winchester

Cathedral Record, pp.29-31.

Ballantyne, A. et al. 1988, "The problems of dewaxing', Preprints for the UKIC 30th

anniversary conference. London, pp.135-41.

Bellamy, L. J. 1975, The Infrared Spectra of Complex Molicules. London.

Burnstock, A. and White, R. 1990, 'The effects of selected solvents and soaps on a

simulated canvas painting.'Cleaning. Retouching and Coatings. (Preprints of the the

contributions to the Brussels Congress) IIC, London.

Cather, S. & Howard, H. 1986, 'The use of wax-resin preservatives on English

medieval wall paintings: rationale and consequences', Case studies in the

conservation of stone and wall paintings (Preprints of the IIC Bologna Congress),

pp.48-53.

Central Council for the Care of Churches. 1959, The Conservation of English

Wallpaintings. being a report of a Committee set up by the Central Council for the

Care of Churches and the Society for the Protection of Aincient Buildings. London.

Church, A. H. 1901, The Chemistry of paintis and painting. London.

Church, A. H. 1904, Treatment of decayed stonework in the Chapter House of

Westminster Abbey. London.

Courtauld Institute of Art, Conservation of Wall Painting Department, 1990.

'Chapel of Our Lady Undercroft, Canterbury Cathedral. Report on Cleaning Tests

on the Vault and Screen', Unpublished.

Derrick, M. 1989, 'Fourier Transform Infrared Spectral analysis of natural resins

used in furnature varnishes.' J.A.I.C. 28. pp.43-56.

Eastlake, C. L. 1847, Materials for a History of oil painting. London.

Fletcher, K. 1988, 'The practical use of some flourescent dyes in the characterisation

of varnish layers in cross-section and the subsequent cleaning of some paintings

using the methods developed by Richard Wolbers', Unpublished, Courtauld

Institute.

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Getty Conservation Institute. 1991, Methods in Scientific Examination of Works of

Art: Infrared Microspectroscopv.

Goodrich, B. F., CAROPOL Water Soluble Resins. Technical data. Ohio.

Hedley, G. 1980, 'Solubility parameters and varnish removal; a survey.' The

Conservator 4, pp. 12-28.

Hedley, G. et al. 1990, 'A study of the mechanical and surface properties of oil paintfilms treated with organic solvents and water.'Cleaning. Retouching and Coatings.(Preprints of the the contributions to the Brussels Congress, 3-7 September, 1990.)

IIC, London.

H.M.Office of Works, 1929, 'Methods of preserving mural paintings in the Chapter

House of Westminster Abbey/ The Museums Journal, vol.28, no.12.

Horie, C. V. 1987, Materials for Conservation. London.

Howard, H. 1988, 'Blue Pigments in English Medieval wall paintings', Unpublished,

Courtauld Institute.

Hluvko, S. 1991, 'Red Pigments in English Medieval Wall Paintings', Unpublished,

Courtauld Institute.

Keyser, C. E. 1883, List of Buildings...having Mural...Decorations. London.

Low, M. J. D and Baer, N. S. 1977, 'Application of Infrared Fourier Transform

Spectroscopy to problems in Conservation. I. General Principles', Studies in

Conservation. 22.

Macregor, E.A ,Greenwood, C.T, 1980, Polymers in nature. London.

Meilunas, R.J, Bentsen J.G. and Steinberg A. 1990, 'Analysis of aged paint binders

by FTIR spectroscopy'.Studies in Conservation. 35. pp.33-51.

Mills, J. and White, R. 1987, The Organic Chemistry of Museum Objects. London.

Mora, L., Mora, P. and Philippot, P., 1984, Conservation of Wall Paintings. London.

Newman, R. 1980, 'Some applications of Infrared spectroscopy in the examination

of painting materials', J.A.I.C.. 19. pp.42-62.

Noppen, J. G. 1932, 'The Westminster Apocalypse and its source.' The Burlington

Magazine. Vol.61, pp.146-159.

Oakeshott, W. 1981, 'The Paintings of the Holy Sepulcre Chapel' Winchester

Cathedral Record, pp. 10-15.

Park, D. 1980, 'The wall paintings of the Holy Sepulchre Chapel' Medieval Art and

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Architecture at Winchester Chathedral. (British Archiological Assosiation

Conference Transactions), pp.38-62.

Perry lithgow Partnership, 1983, Report on the wall painting in Holcot church.

Unpublished report.

Scott, G. G. 1861, Gleanings from Westminster Abbev. London.

Scott, G. G. 1863, Gleanings from Westminster Abbev. London.

Southall, A. 1988, 'New approach to cleaning painted surfaces', Conservation News

.37. pp.43-44.

Southhall, A. 1989, 'Wolbers'cleaning methods', Conservation news .38. pp.12-13.

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paintings', Victoria and Albert Museum.

Tristram, E. W. 1944, English Medieval Wall Paintings: The 12th Century. Oxford.

Tristram, E. W. 1950, English Medieval Wall Paintings: The 13th Century. Oxford

Tristram, E. W. 1955, English Medieval Wall Paintings: The 14th Century. London.

Turner, B. 1985, 'The patronage of John of Northampton. Further studies of the

wall paintings in the Westminster Chapter House.' Journal of the British

Archeologists Assosiation. Vol.138, pp.89-101.

Van't Ehrnreich, E. H. 1970, 'Infrared Microspectroscopy for the analysis of old

painting materials.'Studies in Conservation, 15.

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Tranactions of the London and Middlesex Archaeological Society. 4.

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pp. 168-202.

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contributions to the Brussels Congress)

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Paintings.' The Getty Conservation Institute. (Unpublished).

Appendix 1

Recipes for wax and wax resin preservatives advocatedbv Professors Church and Tristram.

A. H. Church. Published in Keyser (1883, xciii),

described as a 'preservative'.

2 oz. by weight pure white beeswax.

6 oz. by measure oil of spike

lavender or oil of orange peel.

10 oz. picture copal varnish.

26 oz. freshly distilled

spirits of turpentine.

Preparation; Melt beeswax, pour into the oil of spike;

warm until clear, then add copal and turpentine.

Application; warm with 'broad flat soft brush' or, if

colour 'easily detached, with spray.

Gambler-Parry. 'Simplified* by Church and

published in Church (1901:123), described as a

'medium*.

8 oz. oil of spike.

2 oz. by weight elemi.

2 oz. oil of turpentine.

4 oz. by weight pure white wax.

20 oz. by measure 'picture'-

copal varnish or 16 oz. oil-

copal varnish.

Preparation; Warm oil of spike over water to 80C,

add elemi and shake until dissolved; filter warm

solution; heat oil of turpentine over water to 80C;

mix thoroughly; heat over water to 80C, add melted

wax; shake thoroughly; add varnish with constant

agitation; allow water to boil under the mixture for 5

minutes, remove, dry and cool.

A. H. Church. Published in Church (1901:122 and

323-24), described as a 'preservative and medium'.

12 oz. of spike or non

-refinable oil of turpentine.

4 oz. by weight paraffin wax

(melting point 58-62C) or of

ceresin or a mixture of these.

20 oz. 'picture' copal-

varnish or 16 oz. oil-copal

varnish (containing a

sufficiency of oil).

Preparation; Warm oil of spike over boiling water,

add wax and mix thoroughly at 80C; add copal slowly

mixing constantly.

Application; Diluted with spirits of turpentine or

toluene.

E. W. Tristram, published in Tristram 1926,

described as a 'preservative'.

1 part beeswax.

6 parts by volume rectified spiritsof turpentine.

1% Unseed oil.

Preparation; Melt the beeswax and add the other

ingredients.

Application; lightly with a brush or, if the surface is

'too friable', dilute with more turpentine and spray

on. Polish lightly with a rag two or three times during

the following fortnight.

1.

Xylene

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

69/9.3/21.72

3.

White Spirit

H2O

Carbopol 934

Ethomeen C-12

Propan-2-ol

71.6/9.3/19.1

5.

White Spirit

H2O

Carbopol 934

Ethomeen C-12

Propan-2-ol

Acetone

74.5/10.5/15

7.

Xylene

H20

Carbopol 940

Ethomeen C-12

Propan-2-ol

Acetone

68.7/13.4/17.9

9.

White Spirit

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

76/8/16

11.

White Spirit

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

Acetone

71.2/13.1/15.7

50ml

lml

lg7.5ml

10ml

50ml

lml

lg6ml

30ml

50ml

2.5ml

lg6.5ml

15ml

10ml

50ml

5ml

lg7.5ml

10ml

20ml

50ml

lml

lg7ml

20ml

50ml

lml

lg9ml

15ml

20ml

Appendix 2

Solvent gels formulae1

2.

Xylene

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

76/7.2/16.8

4.

White Spirit

H2O

Carbopol 934

Ethomeen C-12

Propan-2-ol

Xylene

79.3/6.9/13.8

6.

White Spirit

H2O

Carbopol 934

Ethomeen C-12

Propan-2-ol

78.7/7.2/14.1

8.

Xylene

H2O

Carbopol 940

Ethmeen C12

Propan-2-ol

Benzyl Alcohol

69/9.4/21.6

10.

White Spirit

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

Acetone

76.9/10/13.1

12.

White Spirit

H2O

Carbopol 940

Ethomeen C-12

Propan-2-ol

Benzyl Alcohol

77/7.7/15.3

50ml

lml

lg7.5ml

10ml

50ml

lml

lg6ml

15ml

10ml

50ml

lml

lg6.5ml

15ml

50ml

5ml

lg7.5ml

10ml

20ml

50ml

lml

lg7ml

10ml

10ml

50ml

lml

lg7ml

10ml

10ml

1 All solvents used were GPR quality except for the White Spirit which was manufactured by Langlowproducts Ltd. with an aromatic content of 15-25% v/v.* Solveny parameters: dispersion/ dipolar/ hydrogen bonding.

Appendix 3

Teas Chart showing the solvency parameters of the most effective solvent gels in relation tothe solubility region of beeswax.

10 20 30 40 50 . 60 70

Dipolar force

80

Solubility region of beeswax (Horie 1987)

Appendix 4

Solvent Gel Tests.

Summary of results reported in the proformas.

Holcot Church.

Test Gel Clearing Application Intev. Cleaning Effect,

no. no.1 Method.2 Time.3 layer.4 wax layer only.5 Sample.6

1. 7. Xylene/H20 10/30 + + + HO8/565 & HO8b/566

2. 7. Xylene/H20 20/60 + + + + HO9/567 & HO9b/568

3. 8. Xylene/H20 15/60 + +

4. 2. Xylene/H20 15/90 + + + HO10/568

5. 9. WS/H20 20/120 + + +

6. 7. Xylene/H20 10/60 * ++ HOll/569

7. 7. Xylene/H20 10/60 * + + + + HO12/570

Tests 6. and 7. took place on the same area.

Holv Sepulchre Chapel. Winchester Cathedral.

+ + + + HS7/571

+ HS8/572


Westminster Abbey Chapter House

+ + + WA8/558 & WA9/559

+ + + + WA13/563

+ + + WA1O/56O

15/120 + + +


1.

2.

3.

4.

5.

7.

7.

8.

11.

1.

Xylene/H20

Xylene/H20

Xylene/H20

WS/H20

Xylene/H20

10/60

10/60

10/90

10/90

10/90

1.

2.

3.

4.

5.

6.

7.

7.

7.

1.

1.

11.

Xylene/H20

Xylene/H20

Xylene/H20

Xylene/H20

Xylene/H20

WS/H20

15/90

0/120

15/120

15/90

15/90

15/120

1 Appendix Proformae

2 Solvent followed by water, both with cotton wool swab.

3 Static/agitation time in seconds.

4 Intervention layer of Japanese tissue.5 Key: + Little or no effect.

+ + Limited effect.

+ + + Partial wax removal.

+ + + + Substatial level of cleaning.

+ + + + + Complete removal of wax layer.

6 Samples HO8/565 and HO9/567 were taken before clearance with water.Samples HO8b/566 and HO9b/568 were taken after both xylene and water clearance was carried out.

Appendix 5

Fourier Transform Infrared Spectra.

All spectra were carried out on a Perkin Elmer 1710 FTIR in diffuse reflectance mode. Allspectra have undergone conversion to Kubalka-Munk units.

Fig.l. Holcot Church. Sample HO2. Waxy surface coating. (KMHO2)

NAX=1.48 T

fHff=8.32 T

3566 3860 2598 2698 1568 CH-1 1888

Fig.2. Holy Sepulchre Chapel, Winchester Cathedral. Sample HS3. Waxy surface coating.

(KHS3A)

-1728

1888 CH-1 588

II

Fig.3. Westminster Abbey Chapter House. Sample WA3B. Waxy surface coating.(KWA3B)

MftX=2.73 T

u

s

*l*/ v\

I

/\

! niN=e.32

i *rl i

-v,

4*88 3538 2508 2999 1588 CIM 1888

Fig.4. Westminster Abbey Chapter House. Sample WA2B. Lower resinous layer.(KWA2B)

=i.37 T

■839 3588 3888 2589 2988 1588 Cil-t

Ill

Fig.5. Clearance test model. Sample SRI.

Wax coating on panel before testing. (KSRl)

IM=7.07 T

11111=9.32 T

4909 3560 3660 2560 2090 1500 1096 Cll-l

Fig.6.Clearance test model. Sample SR2.

Residues of wax coating after testing. (KSR2)

6 3

4000 3586 3086 2590 2860 1586 1690 Cll-l 568

IV

Fig.7. Clearance test model. Sample SR3.

Paint surface before testing. (KSR3)

<=4,48 T

11111=9.32 T

4988 3589 3088 2588 2889 1508 16130 Cll-l 500

Fig.8. Clearance test model. Sample SR4.

Paint surface after testing. (KSR4)

3588 3908 2509 2888 1588 1088 CIH 599

Fig.9. BDH Beeswax, white. (Prod. 33017) (KMBW3)

4888 35

Fig.10. Ethomeen C-12 (KC12)

HIN=B.32 T-^ r

4808 3588

VI

Fig.7. Carbopol 940 (KC940)

Appendix 6

Nitromors Paint Stripper

'Nitromors' is produced by Henkel Home Improvements and Adhesive Products.

'Nitromors Original' was introduced in the 1940s, and the formula has remained almost

unchanged until the 1980s. The basic gelling agent is a small amount of cellulose acetate

and paraffin wax. The solvents were dimethylchloride and methanol. There was no

surfactant or base included, and it was washable with white spirit or IMS.

Water washable Nitromors was introduced in the 1960s. The gelling agent in this case were

paraffin wax and methyl cellulose, CELACOL MMPR1, (approximately 1.2% methyl per

glucose unit) and was produced by Courtaulds Ltd. The main solvents, as with the earlier

version, were dimethylchloride and methanol. Until the 1970s a non-ionic surfactant was

included. In the 1980s this was substituted with an anionic surfactant. In 1987 this was

replaced by a carboxylic acid amine salt (with one end neutralised and the other not). At

this date also the dimethylchloride was reduced in favor of the methanol. Borax nitrite was

also included as a corrosion inhibiter. This was recently replaced by a different corrosion

inhibiter, the nature of which is proprietary information.

Due to the very low water content of the product, the pH value is of limited significance.

However in British Standard Tests Nitromors was found to be not more basic than 5ml of

0.1m HC1 per 20g H2O, and its acidity was low enough not to react with methyl red

indicator. In their own titration tests at a concentration of 10% in water the manufacturers

gave a figure of pH 9.

(pers.comm. Mr Andrew Wood, Chemist at Henkel Home Improvements and Adhesive

Products.)

Appendix 7

Solvent Gel Tests Carried out in the

Chapel Of Our lady Undercroft, Canterbury Cathedral.

The first Carbopol solvent gel tests carried out on wall paintings by the Courtauld

Institute were undertaken in 1990 in collaboration with the Canterbury Cathedral

Wallpaintings Workshop, on the painted vault of the Chapel of Our Lady

Undercroft. The aim in this case was to produce a gel that would dissolve the thin

waxy coating applied by earlier restorers so that the more complex problem of a dirt

layer, which lay directly over the paint surface, could be removed. The gels

developed for the work at Canterbury contained relatively polar solvents and

therefore an aqueous-based gelling system could be used. Two amines were tested

to neutralise the Carbopol, Trietanolamine (TEA) and Ethomeen C/25 . The

Ethomeen C-25 (Polyoxyethylene(15)cocoamine) has cationic surfactant properties

with an HLB value of 19. Both achieved the necessary level of neutralisation (PH 7

to 7.5) at acceptable percentage volumes, however due to the possible complications

in the clearance of a surfactant from the painting surface, the TEA was used in the

final formulation. (Courtauld Institute Report, 1990).

CIA/ GCI Conservation ofWall Paintings Department. 1990-1991

An investigation into the use ofsolventgelsfor the removal ofwax-based coatings on WallPaintings.

Tobit Curteis

Sample nos.HOI - HOI 2

Accession nos. 531 - 533 & 565 - 570

County. Nor thamptonshire.

Village/Town.Holco t.

Position of painting.

North wall of the North aisle.

Name of Building.

St. Mary and All Saints

Church, Holcot.

Name/Address of Custodian.

Rev. A.J.Watkins

The Vicarage, Station road,

Brixworth, Northants.

NN6 9DF.

Permission granted. 28.1.91

Dimensions of Painting.

54 ft. long by 12 ft. high.

Subject. There are a number of subjects

depicted. Tristram identifies among others

a martyrdom of St.Thomas of Canterbury.

The test area was on the lower tier of

subjects, in the area of six standing

Apostles.

Attribution & Date.Early 14th Century.

Date. 18.2.91 Sampled by. Tobit Curteis.

Previous Recorded Surface Treatments

Date.Pre. 1950 1983

Conservator. E.W.Tristram. ? The Perry Lithgow Partnership.

Method

employed.All paintings in

the church were

coated with a

preservative treatment

of a wax based

mater iJal.

An examination was made of all the

paintings in the church but

conservation work was only carried

out on those in the south aisle (west

wall). The wax and possibly resin

coatings on this area of painting was

removed with Nitromors and methyl

chloride. Old repairs were replaced

with lime mortar fills, and the area

made sound.

Area

Treated.North aisle.

South aisle,

South aisle, west wall.

Location of

records. None.

The Perry Lithgow Partnership

samples

& location.

NoneNone.

Sheet no.2

Area Sampled (before testing)

stratieraDhv 1# Stone/rubble substrate. 2. Single layer of plaster. 3. Limewash^ p y' ground. 4. Pigment layer. 5. Waxy coating with thick deposits of

ambient dirt. In some areas there is the remains of a limewash

layer between the paint, layer and the wav.

Possibletechnique. Probably a mixture of lime and organic secco binder.

General Variable. Some areas are very sound, but there are also extensive

condition. areas of decohesion and resulting flaking in the paint layer. The

Whole painting is covered by a thick layer of surface dirt.

Appearance& yellowy translucent amorphous material homogeniously coating thedistribution

whole area of the painting. Relatively thick for such a wax layer.

ofsurfaces In many cases it fills old losses, however there are a number ofcoatings. recent losses that penetrate the wax coating.

UV Homogeneous fluorescence with a greenish tinge over the entire areaexamination. of the coating. Losses stood out clearly through their

non-fluorescence.

Positionof A11 sampies were taken in the area of the'knife'of the standingsamples. figure second from the right.

Possible anomaliesof area sampled. Sample H07 was taken through the coating in an area where

limewash remained over the red pigment layer. During sampling the

coating and limewash separated from the red original surface layer.

ftvpe & area) Tne area of tne tests wax recorded in both general and macro withKyv ' Ilford FP4 (black & white) and with Agfachrome CT100

(transparencies).

Comments.

The presence of areas of limewash between the waxy coating and the

paint surface suggests that this area was uncovered in an early

restoration of the paintings. Preliminary examination shows little

or no dirt on the original surface beneath the coating, suggesting

that it was coated soon after it was uncovered (maybe even in the

same campaign). There appear to be large area still to be uncovered

on this wall, and there also appear to be areas of palimcest.

Sheet no.

Position of Samples

Site. Holco t Chur ch Date. 18.2.91

Sample Reference

Sheet no.

Sample

number.

Accesion

number.

Type of

analysis.

Date.

HOI Sample damaged.

H02 ***

H03 ***

H04 531

H05 Sample damaged.

H06 532

H07 . 533

H08 565

HO8b 566

H09 567

FTIR

FTIR

X-Section/SEM

X-Section

X-Section

X-Section

XSection

X-Section/SEM

19.2.91

19.2.91

18.2.91

18.2.91

18.2.91

18.2.91

18.2.91

18.2.91

Sheet no.

Solvent Parameter Tests

Site. Holcot Church Date. 18.2.91

Solvent.

Xylene

Xylene

IMS

Xylene

IMS

Xylene

IMS

Acetone

Acetone

Acetone

Xylene

Acetone

Xylene 2

2

1

1

1

2

2

1 "

1

1

1

Method/Time

of application.

Swab

Swab

Swab

Swab

Swab

Swab

Swab

Result.

WS Swab

substantial amount of the coating is removed.

Cleaning action is a little quicker than above

and a greater part of the coating is removed.

Action is slower but cleaning is more

thorough than above. Curious result!

Greatly reduced and far slower cleaning

action.

No apparent effect.

Strong and relatively fast cleaning action.

more effective than the above in terms of both

speed of action and amount of material

removed from the surface. Possibly too fast

for safe cleaning.

No apparent effect.

FURTHER TEST OVERLEAF

Conclusions

The coating was clearly very soluble in a range of

solvents particularly in a mixture of aromatics. It was

surprising that it appeared to be soluble in white spirit

in its^pure form considering that the WS used in the tests

had an aromatic content of 15-25% vol/vol. Combinations of

xylene and acetone appeared to have the greatest effect on

the coating. With the exception of the WS result the test

results are consistent with the coating consisting mostly

of beeswax.

Sheet no.

Site.

Solvent.

Holcot Chur ch

Method/Time

of application.


Date. 18.2.9

Result.

1

Propan-2-ol

WS

H2O

Propan-2-ol

Propan-2-ol

Acetone

Triton X-100

Xylene 3

H2O 5

1

4

1

1

1

Swab

Swab

Swab

Swab

Swab

Slow action but the cleaning; effect appears

relatively thorough.

No effect.

Very limited effect.

Some limited effect. Better than 100% P-2-ol

Reasonable speed and depth of action.

(Clearance was carried out by swabbing with

both Xylene and H2O).

Conclusions

Sheet no

Sample Analysis Before Gel Tests

Sample no. HO 2 Accession no. ***** Date. 19.2.91

Hot Stage Examination.

Temp. Observations.

30C White/yellow amorphous translucent

material with inclusions of dirt and

white crystalline material.

65C Body of material begins to melt.

65C Majority of material melts.

67C The melted material flows free from the

white crystalline matrix (calcium

carbonate from the painting?)

>100C No further change.

Conclusions.

It appears possible that the majority of the material is wax,

possibly beeswax, contaminated with a mixture of surface dirt and

calcium carbonate from the surface of the painting.

Sample no. H03 Accession no. ***** Date. 19.2.91


Temp. Observations.

30C As for H02.

64C The majority of the material begins

to melt.

66C Waxy material flows free from the white

crystalline matrix.


Conclusions.

The two samples were both taken from the edge of a loss where the

coating had gathered in a thick mass. The slight difference in

their action under TMA might be explained by the varying levels of

contamination in each sample, as well as the different thickness of

each sample.

Sheet no

Sample Analvsis Before Gel Tests

Sample no. HO 3 Accession no. Date. 19.2.91

Temp.

30C

64C

66C

>100C


Observations.

As for HO2.

The majority of the material begins

to melt.

Waxy material flows free from the white

crystalline matrix.

No further change.

Conclusions.

The two samples were both taken from the edge of a loss where the

coating had gathered in a thick mass. The slight difference in

their action under TMA might be explained by the varying levels of

contamination in each sample, as well as the different thickness of

each sample.

Notable Absorbtion Peaks

F.T.I.R.

Interpretation.

Conclusions.

Sheet no

X-Section Examination Before Gel Tests

Sample no. HO 7 Accession no. 533 Date. IS.2.91

Examination Unmounted,

Surface. The surface consists of a course red pigment and is

not coated with the wax layer as this separated in the

sampling procedure.

Stratigraphy.Red pigment layer over a white crystalline ground with

inclusions of a course yellow pigment.

Examination Mounted

Normal Light (Tungsten Source)

Graphic record of sample.

Photography: Film Type Fugichrome 160 Mag.no.100/200

Film nos.

Comments.

1. Red crystalline pigment, possibly red ochre. The

pigment layer is not bound by calcium carbonate so

there is probably a secco medium present. This is not

visible at mag. x400.

2. White crystalline matrix (calcium carbonate).

3. Small red and yellow crystalline pigment particles

Photographic records of this sample appear to have a

translucent coating on the surface. This is in fact

due to the polyester mounting resin, and not a wax

or resin coating.

Sheet no

X-Section Examination Mounted Before Gel Tests

UV Source

Sample no. HO? Accession no. 533 Date. 18.2.91


Photography: Film Type. ##### Mag.no. Filmnos.

Comments.

1. Very little fluorescence from this layer although thereel colour could clearly be seen under UV.

2. Bright whitish fluorescence

Staining

Type. Acid Fuchsin 2% vol/vol in H20. Rinsed with H20.

Results.

A weak stain was seen in the upper half of layer 2 of the

sample. No stain was apparent in the pigment layer probably

due to the red pigment disguising the light pink stain. The

conclusion would appear to be that there if some

proteinous material included in the limewash as and

additional binder. This may imply that the binder for the

pigment layer is also a protein.

Sheet no.

Site.

Solvent gel.

Holcot Church

Method/Time

of application.

Solvent

Date.

Gel Tests

8

Result.

.3 .9 1

1/ 7

2/ 7.

3/ 8.

4/ 2.

5/ 9.

Swab, 10/30.

Swab, 20/60.

Swab, 15/60.

Swab, 15/90.

Swab, 20/120.

Cleaning action appears to be quite

effective and fast, especially

towards the centre of the test area.

Clearance: xylene/H20. Samples: HO8a/HO8b

Action similar to test 1, but

proportionally more coating is removed,

due to the extended time period.

Fairly good level of cleaning.

Clearance: xylene/H20. Sample: HO9.

Slower action than above. Coating

appeared to be thinned but to a lesser

extent.

Clearance: xylene/H20.

Relatively good action with partial

removal of the coating.

Clearance: xylene/H20. Sample. HO10.

Slow cleaning action but a homogeneous

thinning action. Less than test 2.

Clearance: white spirit/H2O

FURTHER TESTS OVERLEAF

Conclusions

Test 2 and 6/7 appeared to give the most satisfactory

levels of cleaning with virtually all the coating being

removed. Under UV illumination this also appeared to be the

case. In niether case did there appear to be any surface

damage caused by mechanical action.

It seems likely that the clearing procedure is actually

responsible for a substantial amount of the cleaning

action.

(Samples HO11 & HO12 were taken from an area that may have

lost its surface layer due to earlier damage.)

The surface temperature of the wall at the time of the

tests was 8C. The ambient temperature was 12.5C and the

RH was 7 7%.

Sheet no.

Site.

Solvent gel.

Holcot Church

Method/Time

of application.

Solvent

Date.

Gel Tests

Result.

8 .3 .9 1

6/ 7.

7/

Swab, 10/60.

Intervention

layer.

Swab, 10/60

Intervention

layer.

The gel swells the surface coating but

does not remove it. Removal takes

place during clearance when the

vulnerable, swollen material is lifted

off by the swab.

Clearance: xylene/H2O. Sample: HO11

Similar action to the above. Overall

cleaning effect on the area after two

tests is similar to test 2.

Clearance:xylene/H2O. Sample: HO12.

(Tests 6 & 7 took place over the same area.)

Conclusions

Sheet no


Sample no. HO 4 Accession no. 531Date.

18.2.91

Examination Unmounted.

Surface.

Surface dust over a thin waxy coating.

Stratigraphy.

Surface dust, waxy costing, red pigment layer, white crystaline

substrate.

Examination Mounted

Normal Light. (Tungsten Source)


Photography: Film Type Fugichrome 160 Mag.no. Film nos.

X100/X200

Comments.

1. Fine white surface 'dust' in some areas.

2. Thick yellowy translucent coating.

3. Pigment layer. Fine red crystalline particles.

4. Possibly a ground layer separate from 5. but interface isvery indistinct.

5. White crystalline matrix, dense and homogeneous.

6. Single red crystals.

7. Two large dark red/black crystals.

Sheet no


UV Source

Sample no. HO4 Accession no. 531 Date. 18.2.91


Photography: Film Type. Ektachrome 6 4 Mag.no. xlOO Filmnos.

Comments.

1. light white fluorescence clearly different from 2.

2. Thick layer fluorescing dark blue/ yellow.

4. & 5. Both fluoresce bright white. Distinction between the

two is made no more apparent in UV.

Type.

Results.

Sheet no


Sample no. HO6 Accession no. 5 3 2 Date. 18.2.91


Waxy coating with small areas of surface dust (extends around

the edge of the sample.

Stratigraphy.

Waxy coating over simple white crystalline mass.

Examination Mounted

Normal Light. (Tunosten Source)


Photography: Film Type Fugichrome 160. Mag.no. xlOO Film nos.

Comments.

HO6 was taken from the edge of an old (pre-wax) loss therefore

the wax has continued around the edge, and beneath the sample.

1. Yellowy translucent coating.

2. White crystalline matrix.

3. White crystalline disruption within wax.

4. Red particle.

5. Large red/black particle.

Sheet no


UV Source


Graphic record of samnle.

Photography: Film Type. Ektachrome 6 4Mag.no. xlOO Fihn nos.

Comments.

1. Dark yellowy/blue layer, with littlff apparent surface dirt2. White bright flourescence..

Stainint

Type.

Results.

Sheet no

X-Section Examination After Gel Tests

Sample no. H08 Accession no. 5^5 Date. 20.3.91


Surface.White crystalline surface with small inclusions of dirt

particles, and possible pigment particles.

raigrapy. Apparentiy Hmewash layer over a limewash ground.

Examination Mounted



Photography: Film Type Fugichrome 160 Mag.no. xl00/x200 Film nos.

Comments.

1. White crystalline layer with small inclusions of pigment

particles.

2. Second white crystalline layer, apparently slightly more

pigmented than 1.

3. Course pigment particle.

There does not appear to be any residues of the wax on the

surface of the sample and no physical or mechanical damage

is apparent.

Sheet no

X-Section Examination Mounted After Gel Tests

UV Source

Sample no. HO 8 Accession no. 5 6 5 Date. 20.3.91


Photography. Film Type. Mag.no. Film nos.

Comments.

Layers 1 and 2 fluoresce with a similar bright whitish

fluorescence, but there is a clear distinction between the

two which is less apparent in visible light. There is no

evidence of any remaining wax coating on the surface of the

sample.

Staining

Type.

Results.

Sheet no


Sample no.HO8ta Accession no. 5 g g Date- 20.3.91


Surface.

White crystalline surface with dark inclusions, probably

mixture of dirt and pigment.

Stratigraphy.

White lime layer over tinted lime background.

Examination Mounted



Photography: Film Type Fug i chrome 160 Mag.no. xl00/x200 Film nos.

Comments.

1. white crystalline surface layer with pigment particles

2. White crystalline layer tinted with yellow and red

(ochre?) particles.

Sheet no


UV Source

Sample no. HO8b Accession no. 5 6 6 Date. 20.3.91


Photography: Film Type. Mag.no. Film nos.

Comments.

Layers 1 and 2 fluoresce in a similar bright way but the

separation between the two is apparent.

Staining

Type.

Results.

Sheet no


Sample no. HO 9 Accession no. ^ 6 ? Date. 20-3.91


Surface.

White crystalline layer with inclusions of yellow pigment

particles. Some areas of waxy material on surface.

Stratigraphy.

Yellow tinted white crystalline layer over similar

background layer.

Examination Mounted



Photography: Film Type Fugichrome 160 Mag.no. xlOO/x2OO Film nos.

Comments.

1. Fine translucent waxy layer broken in some places.

2. White crystalline layer with inclusions of yellow

(ochre?) pigment particles.

3. Dirt particles.

4. White crystalline layer with further inclusions of

yellow pigment particles.

Sheet no


UV Source

Sample no. HO9c /• n

Accession no. Date.20.3.91



Comments.

1. Very little fluorescence from this layer, but clearly

visible against the layers below.

Layers 2 and 3 fluoresce in a similar way.

Type.

Results.


Sheet no

Sample no. HO 10 Accession no. 55s Date. 20.3.91


Surface.

Clear waxy surface with inclusions of red particles.

Stratigraphy.

Waxy coating over a whitish crystalline layer, lower layer

has greater amount of yellow pigment particles than that

above.

Examination Mounted



5.

Photography: Film Type Fug i c h r ome i 6 0 Mag.no. xl00/x200 Film nos.

Comments.

1. Thin waxy layer.

2. white surface layer. Very indistinct separation between

layers 2 and 3.

3. White crystalline layer with yellow and red pigment

par tides.

4. Large yellow crystalline pigment particle.

5. Small red particles.

Sheet no


UV Source

Sample no. HO 10 Accession no. 5 6 8 Date. 20.3.91



Comments.

1. Very little fluorescence.

Similar fluorescence from 2 and 3. The interface between

the two is not clear in this sample.

Staining

Type.

Results.

Sheet no


Sample no. HOI 1 • ^ fi 9Accession no. Date. 20.3.9 1


Surface.Surface appears waxy.

Stratigraphy.

Fine waxy coating on the surface over white crystalline

layer tinted with red and yellow pigment particles.

Examination Mounted



Photography: Film Type Fug i ch r ome 1 6 0 Mag.no. xlOO/x2OO Film nos.

Comments.

1. Very fine waxy layer,

2. White crystalline layer (apparently single) with

inclusions of pigment particles.

3. Yellow and red (ochre?) particles.

Sheet no

X-Section Examination Mounted Alter Gel Tests

UV Source

Sample no. HO11 Accession no. 569 Dale- 20.3.91


Photography: Film Type.^4* ^a ^^ ^^ ^^ Mag.no. FUm nos.

Comments.

1. little or no visible fluorescence.

2. Apparently only a single layer. Fluorescence is quite

bright.

Type.

Results.

Staining

Sheet no




Surface.

Areas of waxy material over white crystalline surface.

Stratigraphy.

Broken waxy coating over white crystalline layer with red

and yellow particles.

Examination Mounted



Photography: Film Type Fugichrome 160 Mag.no. x200 Film nos.

Comments.

1. Broken area of fine waxy coating.


3. Small yellow crystalline particles

4. Large white particle.

Sheet no

X-Section Exaihination Mounted After Gel Tests

UV Source

Sample no. HO12 Accession no. 5 7 0 Date. 20.3.91



Comments.

1. Little or no fluorescence.

2. Single brightly fluorescing layer.

Staining

Type.

Results.

Posilioii of Samples

Sheet no.

Site. llolco t Chui ell Dale. S - 2 . 9 1


An investigation into the use ofsolventgelsfor the removal ofwax-based coatings on WallPaintings.

Tobit Curteis

Sample nos.HS1 - HS8

Accession nos.528 -530, 571 - 572

County. Hampshire.

Village/Town.Winchester.


South wall, West bay.

Name of Building. Dimensions of Painting.

Winchester Cathedral.

Holy Sepulchre Chapel

Subject.


John Harclachre.

Cathedral Office.

Winchester Cathedral

Resurrection of the dead

Attribution & Date.

Permission granted.

Date.

Date.

Conservator,

13.:

Pre

12.2.91

2.91

. 1900

Unknown.

Jl 1 1 L> i

Sampled by. Tobit Cur


C 1900-1950

E.W.Tristram ?

c.

The

LOU

teis

1959

Eve

•

-1970

Baker Trust

Method

employed.

An unidentified material

possibly copal varnish

was applied to the

surface of the painting.

A coating of

wax preservative

was applied to

the paint surface,

over the

previous coating:.

An area of 13th century

painting on the west side

was removed to reveal the

12th century trumpeting

angel (previously

untreated). The east side

of the painting was

cleaned possibly with

Nitromors paint stripper.

Area

Treated.Eastern section

of the paintingSame area as the Tne wnoie area of theprevious treatment, painting.

Location of

records. None None The Eve Baker Trust

Previoussamples

& location.

None None None

Possible

technique.

Sheet no.2


Apparent lt stone substrate. 2. Rough plaster. 3. Possibly a fine

stratigraphy. layer of plaster in some areas only. 4. Limewash ground.

5.Underdrawing. 6. Limewash layer. 7.Paint layer.

8. Surface coatings.

Calcium Carbonate binder. (Limewash).

General

condition.Paint surface heavily abraded in many areas. Some areas of

active deterioration with severe flaking.

Appearance &

distribution

of surfaces

coatings.

Surface coatings only apparent on the eastern side of the

painting. Dark material with some form of surface residue

and considerable surface dirt.

UV

examination.

Homogeneous distribution of slightly fluorescing coating

on the eastern side of the painting. The residue on the

surface fluoresces a lighter green than the body of the coating

Positionof Central area of the painting close to the central and

samples. right hand angles descending from the cloud to rescue the

souls of the dead.

Possible anomalies In order to take samples of the most suitable areas of

of area sampled. the coating some samples were taken from areas of red

background while others were taken from areas of red.

Photography: The whole area of the painting was recorded in general and

(type&area) in macro with both Ilford FP4 (black & white) and

Agrachrome CT100 (transparencies).

Comments.

The severe abrasion of much of the painting hinders the

reading of the central section. This depicts three small

but delicately drawn angels descending from a cloud to

take up the souls of the dead that can just be discerned

at the base of the scene. This abrasion also reviles many

areas of the red underdrawing which has been exposed when

the black linear painting has been lost. Much of the

outline now visible on the large trumpeting angel on the

left of the scene is this red underdrawing. The situation

is clarified in sample HS6/530 which shows the

stratigraphy of the paint layers.

Sheet no.

Position of Samples

Site. Winchester Cathedral: HSC Date. 13.2.91

Sample Reference

Sheet no.

Sample

number.

Accesion

number.

Type of

analysis.

Date.

HS1 528

HS2 Sample damaged.

HS3 ***

HS4 ***

HS5 529

HS6 530

HS7 " 571

HS8 572

X-Section

FTIR

FTIR

X-Section/SEM

X-Section

X-Section/SEM

X-Section

15.2.91

14.2.91

14.2.91

15.2.91

15.2.91

20.3.91

20.3.91

Sheet no.


Site.Winchester: HSC

Date.13.2.91

Solvent.

Method/Time

of application. Result.

Xylene. Swab.

Xylene 2 Swab.

IMS 1

Xylene 1 Swab.

IMS 1

Xylene 1 • Swab.

IMS 2

Acetone 1

Xylene 1 Swab.

Acetone 1

Xylene 2 Swab.

Acetone 2

Propan-2-ol 1

Xylene 5

H20 5

Triton X-100

No apparent effect on the coating.

Some effect on the coating. Surface

dirt removed but majority of coating

remains in tact.

Greater cleaning effect than above

Surface dirt removed.

Similar/slightly improved cleaning

on the above, but coating still

on surface.

Slower action with less effect than

that above.

Limited slow action.

Swab. Cleaning action appears better than

(Clearance with above, but seems to rely heavily1 Swab of Xylene) on mechanical action of clearance.


Conclusions

The use of non-polar rather than polar solvents appears to

have the greatest effect on the coating, however even when

strongly;aroinatic solvents are applied the effect is limited.

This suggests that there is a component of the coating that is

not readily soluble in standard organic solvents. The

inclusion of a surfactant appears to enhance the effect of the

solvent mixture on the coating, but even in this case it is

not readily dissolved. It is possible that there is are more

than one layer of coating on the painting, and that the

solvents are working on only a single layer leaving the others

more or less untouched. (This may become apparent with X-

section analysis or SEM). There is a substantial amount of

surface dirt that is readily removable with light mechanical

action.

Sheet no.

Site.

Solvent.

Winchester HSC

Method/Time

of application.


Date> 13.2.91 Cont. . .

Result.

Xylene 10

H2O 5

T X-100 1

Acetone

H20 5

T X-100 1

Swab. Greater effect than above, but

(Clearance with majority of coating remains

swab of Xylene) in tact.

Swab.

Swab.

No apparent effect.

Limited effect.

Conclusions

Sheet no


Sample no. HS1 Accession no. 52s Date. 15.2.91


Surface.Fine waxy coating and layer of surface dirt over red

pigment layer.

Stratigraphy.Waxy coating over red pigment on white crystalline layer.

Examination Mounted



Photography: Film Type Ektachrome 64 Ma*no' x2OO/x4OO FlIm nOS"

Comments.

1. Fine dark translucent layer, with areas of surface dirt.

2. Translucent, but material slightly more white and opaque

than 1. Very broken.

3. Whitish crystalline later intimately bound with 4.

4. Red pigment particles, apparently bound in the white

crystalline matrix that surrounds them.

5. Large void.

6. White crystalline material.

Sheet no


UV Source

Sample no. HS1 Accession no. 5 2 8 Date. 15.2.91


Photography: Film Type. ***** Mag.no. Filmnos.

Comments.

1. Yellowy fluorescence.

2. Far less fluorescence than the above. Much darker

3. Bright whitish fluorescence.

Stainlm

Type.

Results.

Sheet no

Samnle Analvsis Before Gel Tests

Sample no. HS3 Accession no. ***** Date. 14.2.91


Temp. Observations.

30C Dark whitish amorphous material apparently

containing some particles of dirt.

66C Some movement of the sample observed.

68C Most of the sample melts freely.

71C Most of the sample is free flowing. There

is a small area of white apparently crystalline

residue.


Conclusions.Although the melting temperature is marginally

than would normally be expected, the majority

of the sample may still be beeswax. It could

be contaminated with certain materials (the white

residue ?) that may disperse the heat, resulting in a

higher apparent melting temperature.

Sample no. HS 4 Accession no. ***** Date. 14.2.91


Temp. Observations.

30C Dark whitish amorphous material containg

particles of dirt, (similar to HS3) .

66C Some melting occurring.

67C Majority of the sample melts at this stage.

68C Majority of the sample is free flowing

leaving a residue of a white crystalline

material.


Conclusions.

Conclusions are as for HS3.


Sheet no

Sample no. HS2 Accession no. Date. i 4 . 2 . 9 i

Temp.


Observations.

30C

235C

245C

267C

272C

300C

Fine white papery material with a fiberous

celluJoser texture.

Some apparent movement in fibrous matrix.

Small voids opening in sample.

Larger voids developing and areas beginning

to darken.

Whole sample undergoes slow darkening.

Whole sample now uniformly darkened.

Conclusions.Charring appears to be occurring above 2 50C

therefore possibly some form of cellulose material


F.T.I.R.

Interpretation.

Conclusions.

Sheet no




Surface. Waxy coating with surface dirt over red pigment layer.

Stratigraphy.Waxy coating with surface dirt over red pigment layer

White crystalline lower layer.

Examination Mounted


Graphic record or sample.

Photography: Film TypeEctachrome 64

Mag.no. Film nos.

X200/X400

Comments.

1. Whitish translucent coating with areas of dirt on the

surface.

2. White crystalline? deposits.

3. Large red crystalline particles. Does not appear typical

of lime/fresco technique.

4. White crystalline layer.

5. Waxy material. Whitish/brown. Maybe some contamination

after sampling.

Sheet no


UV Source




Comments.

1. Yellowish fluorescence.

2. No strong fluorescence.

3. Bright white fluorescence.

4. No apparent fluorescence.

Type.

Results.

Staining

Sheet no


Sample no. HS6 Accession no. 539 Date- 15.2.91


Surface. ., . . n . . .Waxy coating over black pigment layer.

Stratigraphy.

Waxy coating on top of a black pigment layer intimately

bound with white crystalline matrix. Below this is a

separate white layer above a layer of red pigment. Below

this is a second white crystalline layer.

Examination Mounted

Normal Lipht. (Tungsten Source)


Photography: Film Type Ectachrome 8 4 Mag.no. x200/x400

Comments.

1. Translucent whitish coating.

2. Areas of more opaque translucent material.

3. Corsly ground charcoal black pigment in white

crystalline matrix (lime).


5. Red (ochre?) pigment layer. Quite pigment thin


Sheet no


UV Source

Sample no. HS6 Accession no. ^ ^ 0 Date. 15.2.91



Comments.

1. Yellowy but fairly weak fluorescence

2. Apparently no fluorescence.

3 & 4. Bright white.

Type.

Results.

Staining

Sheet no.

Site.

Solvent

Winchester

gel.

. HSC.

Method/Time

of application.

Solvent Gel Tests

Date.

Result.

1 1 .3 .9 1

1/ 7.

2/ 7.

3/ 8.

4/ 11

Swab 10/60.

Swab 10/60.

Little or no cleaning effect.

Clearance: xylene/H2O.

no further effect.

Clearance: Xylene/H20. Sample: HS7.


Swab 10/90.

Swab. 10/90

to the removal of surface dirt

5/ 1. Swab 10/90.

Apparently little or no effect.

Possible that some gel remaining on

the surface after clearance.

Clearance: xylene/H20.

No material visibly removed from

the surface, but the surface has

a shine after cleaning. Maybe due

Clearance: WS/H2O. Sample: HS8.

Again no visible cleaning effect.


Conclusions

There appeared to be almost no effect on the surface

coating* suggesting that it is a hard resin with no wax

component. Surface dirt is removed and a shine is left on

the surface, so it is possible that residues of some

material are being removed from the surface. (I.E. the

residues of Tristrams wax treatment that had been mostly

removed in the 1960s.)

True results will only be apparent under SEM or

visible microscopy.

The surface temperature of the wall at the time of the

tests was 15C The ambient temperature was 16c and the RH

was 6 7%.

Sheet no.

Site.

Solvent gel.

Method/Time

of application.

Solvent Gel Tests

Date.

Result.

Conclusions

Sheet no


Sample no. HS7 Accession no. 571 Date. 20.3.91


Surface.

Fine waxy coating over reel pigment.

Stratigraphy.

Fine waxy layer over red pigment rich layer. White

crystalline lower layer.

Examination Mounted


Graphic record or sample.

Photography: Film Type Ektachrome 6 4 Mag.no. x20 0/x40 0 Film nos.

Comments.

1. Whitish translucent surface coating.

2. Red crystalline pigment rich layer with white

white crystalline binder.


Sheet no


UV Source

Sample no. HS7 Accession no. Dale. 20.3.91


Photography: Film Type. * He *** Mag.no. Film nos.

Comments.

1. Dark yellowy fluorescence.

2. No apparent autofluorescence.

3. Bright white.

Type.

Results.

Staining

Sheet no


Sample no. HS8 Accession no. 572 Date. 20.3.9 1


Surface.

Waxy surface over white layer.

Stratigraphy.

Fine waxy coating over white crystalline layer with small

areas of red pigment. Second white crystalline layer below

Examination Mounted



Photography; Film Type Ektachrome 64 Mag.no. xl00/x200 Film nos.

Comments.

1. Small area of red pigment particles in a white

crystalline matrix.

2. Translucent coating.


4. Second distinct white crystalline layer.

5. Second area of red pigment.

Sheet no


UV Source

Sample no. HS8 Accession no. 5 7 Date. 20.3.91



Comments.

1. Weak yellowy fluorescence.

2. and 3. fluoresce in the same bright white fashion* but

in UV there is more of deliniation between the two than in

normal light.

Staining

Type.

Results.

Position of Samples

bheet no.

Site. Winchester Cathedral: NSC Date. 13.2.9]


Sheet no.

Site. W. A. C. H. Date. 23.1.91

Solvent.

Method/Time


Xylene

Propan-

Xylene

Propan-

Xylene

Propan-

Acetone

White s

White s

1

2-ol

2

2-ol

2

2-ol

pir it

p i r i t

1

2

1

•

2

Swab

Swab

Swab

Swab

Swab

Propan-2-ol 1

White spirit 1 Swab

Propan-2-ol 1

Toluene. Swab

Toluene 1 Swab

Benzyl alcohol 1

Some action apparent, possible

swelling of surface coating:, and some

material removed.

Marginally better results than above.

Action is less than the above two

tests. Apparently certain material is

removed and then action stops.

No apparent action.

No apparent action.

No apparent action.

Some slight effect. Small amount if

material is removed, including surface

dirt.

This appeared to have some effect. It

was unclear what it was removing but

there did appear to be a certain amount,

of material absorbed into the swab.


Conclusions

The tests indicate that there area large areas where there are

two coatings present. One of these, the lower (and earlier) is

almost insoluble in solvent mixtures. This is probably the

varnish (perhaps copal) applied by Scott. Above this is a

second very broken and thin coating. This is probably the v/ax

applied by HMG. It is readily soluble in a range of aromatic

solvents. In the centre of the picture its is very thin

presumably because the majority of it was removed by EH in

1985. Towards the edge of the painting where it is obscured by

the pillars this upper waxy layer survives far thicker.

It appears that any gel would be aimed at this upper layer

only, and an alternative method should be used to tackle the

lower layer if this was considered to be desirable.


Sheet no.

Site. W.A.C.H. Date. 23. 1 .91

Solvent

Method/Time


Toluene 2 Swab.

Benzyl alcohol 1

Xylene 2 Swab

Benzyl alcohol 2

Xylene 2. Swab

Benzyl alcohol 1

Acetone 1

The top (waxy) layer dissolves readily

but the problem occurs when the second

layer is reached. This appears to be

insoluble in solvent mixtures. A test

with this mixture was carried out in an

area where the waxy layer appeared

to be directly over the stone substrate

Here all the coating was readily

removed.

Very similar in effect to the above

test.

Again very similar to the above two

tests.

Conclusions

Sheet no


Sample noWA 1 WAI Accession no. * * ** Date. 3 0.1.91

Temp.

30C

192C

2 4 8C

300C


Observations.

Dark brown/yellow resinous material, quite

hard and brittle, with inclusions of surface

dirt.

Slight darkening observed.

Darkening observed throughout.

Further darkening occurs. Sample now dark

brown and opaque.

Conclusions.

Sample possibly consists of a hard resin

such as copal.

Sample no. WA2 Accession no. * *** Date. 3 0.1.91

Temp.

30C

58C

62C

64C

68C

>100C


Observations.

Translucent amorphous whitish material, with

inclusions of surface dirt and white

crystalline material.

Some movement occurs.

Sample begins to melt.

Melting occurs throughout the sample.

Material free flowing leaving white crystalline

material unaffected.

No further change.

Conclusions.

The melting point suggests that the sample

consists mostly of a wax, probably beeswax.

The white crystalline material is probably

a contaminant from the wall. Soluble salts?.

Sheet no

Sample Analysis Before Gel Tests

Sample no. Accession no. Date.

Temp.


Observations.

Conclusions.


F.T.I.R.

Interpretation.

Conclusions.

Sheet no


Sample no. WA4 Accession no. 501 Date. 2 8.1.91


Surface. Thick translucent layer covers surface of the sample. Apparentlywhite layer below.

Stratigraphy.1. Waxy layer, 2. Resinous layer, 3.Paint Layers containing blue

pigment particles. The paint layers appear to be saturated with

the waxy material.

Examination Mounted



Photography: Film Type Ektachrome 6 4 Mag.no. x100/x200 Film nos-

Comments.

1. Sur face dirt.

2. Thick resinous layer, translucent yellow/brown

3. Carbon black? particles.

4. Small amounts of surface dirt at interface.

5. Translucent coating similar to 2.

6. Disrupted white material.

7. Dark particles-carbon black?

8. Opaque white layer. Broken in places.

9. Further original surface dirt.

10. Original surface?


UV Source

Sheet no

Sample no. WA4 Accession no. 501 Date. 29. 1 .91



Comments.

1. Yellow/green fluorescence.

2. White fluorescence.

3. As above.

4. Dark purple.

5. White disrupted layer.

6. Bright white.

7. Light purple.

Type.

Results.

Sheet no


Sample no. Accession no. 5 0 Date. 2 3.1.91


Surface.Yellowy waxy surface coating with surface dirt

Stratigraphy.1. Waxy material, 2. resinous material. 3. complex mixture of

pigment layers, inc. blue crystalline pigs.

Examination Mounted



Photography: Film Type „, , „ t Mag.no. . Film nos.B v 3 JV Ektachrome 64 xl00/x200

Comments,

1. Yellow brown coating.

2. Surface dirt.

3. Carbon black particles.

4. Disrupted white material.

5. Large dark amorphous lump.

6. Yellow/white crystalline material.

7. Carbon black particles.

8. Yellow crystalline material as in 6.

9. waxy material ?

10. as for 8


UV Source

Sheet no

Sample no. WA6 Accession no. Date. 29.1.91


Photography. Film Type. * *** Mag.no. Film nos.

Comments.

A. Fairly solid and coherent.

B. Very disrupted and broken.

1. Yellow green.

2. light purple-disrupted.

3. White particles.

4. Dull bluish area.

5. similar to 4.

6. Opaque white with orange tinge.

7. bright white.

8. Dark purple.

9. Darker purple/black.

10. Opaque white.

Type.

Results.

Staining

Sheet no


UV Source

Sample no. WA7 Accession no. ^ 0 4 Date. 29.1.9 1


Photography: Film Type. * * ** Mag.no. Film nos.

Comments.

1. White- possibly disrupted waxy material

2. Yellow/green.

3. white particles.

4. as for 3

5. opaque white layer.

6. Less opaque white.

7. light purple.

S. Opaque white with orange tinge.

9. as above, but orange more intense.

10. disrupted white.

Type.

Results.

Staining

Sheet no


Sample no. WA7Accession no.

504Date.

29. 1 .91


Surface.Thick resinous surface coating.

Stratigraphy.

Sample very thin. 1. waxy/resinous coating over 2. white layer

containing light blue crystals.

Examination Mounted

Normal LichL (Tungsten Source)

Granhic record of sample.

Photography: Film Type Ektachrome 6 4 Mag.no. xl00/x200 Filmnos-

Comments.

1. Sur face dirt.

2. Yellow/brown translucent coating.

3. Carbon black particles?

4. Disrupted white crystalline material.

5. Original surface ??

6. Surface dirt from above.

7. Opaque crystalline material broken in places.

Sheet no.

Solvent Gel Tests

Site. W.A.C.H. Date. 13.3.91

Solvent gel.

Method/Time


1/ 7. Swab. 15/90.

2/ 1.

3/ 1.

Swab. 15/90.

Swab. 15/90.

Little apparent cleaning- effect.

Surface dirt and small amount of

coating: removed. Some small bloom

on edge of test. area.

Clearance: xylene/H2O. Samples. WA8/WA9

Again little cleaning effect. Also

some bloom at edges.


9FOC

Very similar to the above. Some of the

bloom removed.



Swab. 120. Does not appear to have any effect on

lower layer.

clearance: H2O.

(Test 9FOC took place over the area of 3. )

4/ 7.

5/ 7.

Swab. 0/120.

Swab. 15/120

Wax layer directly over stone. Shows

good thorough cleaning effect all the

way to the stone substrate.


Good cleaning effect, all the wax

appears to be removed. No bloom.

Clearance: xylene/H2O. Sample: WAI 3.

Conclusions

It seems clear that even gelled solvents have little or no effect

on the lower resionous layer (as was presumed from the solvent

parameter tests.) Gel 7. is the most effective for dissolving the

upper wax coating, and as there is in effect a barrier layer

between the wax layer and the paint surface, there is no danger

to the vulnerable organic components of the painting itself. Care

must be taken to avoid areas of bloom that sometimes occur.

Further examination must be carried out to establish exactly the

source of this bloom.

Position of Samples

Sheet no.

Site. W . A . G . DaLe. 30.1.91

; v

5

Sample Reference

Sheet no.

Sample

number.

Acccsion

number.

Type of

analysis.

Date.

WAI

WA2

WA3

WA4

WA5

WAG

WA7

WAS

WA9

WA10

WAI 1

WAI 2

WA13

WA14

-f* <t- T^ Jf*

50

50

50

1

2

3

#*##

56

56

56

56

0

1

2

3

564

FT I R a 0 . 1 . 9 1

FT1R 30.1.91

FTIR 30.1-91

X-Section 28. 1 .91

X-Section 28.1.91

X-Section 28.1.91

X-Section/SEM 28.1.91

SEM 2 9.1.91

SEM 29.1 .91

X-Section 13.3.91

X-Section 13.3.91

X-Sect ion 13.3.91

X-Section 13.3.91

X-Section/SEM 13.3.91

Sheet no.

Solvent Gel Tests

Site. W. A. C . H . Date. 13.3.91

Method/Time

Solvent. of application. Result.

A9C Swab. 120. Appears to have some cleaning action

on the lower coating, some material

dissolved. After clearance a bluish

fluorescence could be seen under UV on

the area of the test. Some bloom around

the edges (removed with mixture of 1/1

acetone/propan-2-ol).

Clearance: H20. Sample: WAI 4.

6/ 11. . Swab. 15/120. Test 5 was carried out twice over the

same area. On both occasions there

was a negligible result.

Clearance: WS/H2O.

Conclusions

Sheet no


Sample no. WAI 1 Accession no. Date- 13.3.91


Surface.

Thick dark resinous layer.

Stratigraphy.

Thick coating with inclusions of disrupted white material over a

white crystalline layer.

Examination Mounted



Photography: Film TypeEktachrome 6 4

Mag.no.xl00/x200

Film nos.

Comments.

1. Dark translucent resinous layer.2. Dirt and white disrupted material.

3. dense white crystalline layer.

4. Small red crystals.

5. Further disrupted white effluorescence.

Sheet no

X-Section Examination Mounted Alter Gel Tests

UV Source

Sample no. WA1 1 Accession no. ^ 6 * Date. 13.3.91


Photography: Film Type. Mag.no. Film nos.5|C 5C fC 3C

Comments.

1. Yellow/green fluorescence.

2. Dull white.

3. Bright white.

Staining

Type.

Results.

Sheet no


Sample no. WAI Accession no. 5 6 2 Date. 13.3.91


Surface.

Thick dark resinous coating'.

Stratigraphy.The coating lies directly over a red pigment layer on a white

ground.

Examination Mounted



Photography: Film Type Ektachrome 64 Mag.no. xlOO/x2O(Film nos.

Comments.

1. Light red/white layer.

2. Red orange dense pigment layer.

3. Dark blackish material.

4. and 5. White crystalline material

Sheet no


UV Source

Sample no. WA12 Accession no. 5 6 Date. 13.3.91



Comments.

1. Bright white with redish tinge.

2. Orange/red fluorescence-weak.

3. White matrix with orange tinge.

4. Similar to 3. but weaker orange.

Type.

Results.

Sheet no


Sample no. WA13 Accession no. 563 Date. 13.3.91


Surface.

Thick dark resinous layer on surface.

Stratigraphy.

The coating lies over complex pigment and ground layers. Waxy

material is on the bottom of the sample.

Examination Mounted

Normai Light. (Tungsten Source)


Photography: FilmType Ektachrome 64 Mag'no' xl 00/x20rjilmnos'

Comments.

1. Translucent dark resinous material.

2. White crystalline material.

3. Dense white crystalline mass.

4. Red pigment layer in white matrix.

5. Waxy material containing large amount of dark material

(probably dirt and carbon black).

6. Blue crystals.

7 . Red Crystals.

9. Dense white layer.

Sheet no

X-Section Exaihination Mounted After Gel Tests

UV Source

Sample no. WAI 3 Accession no. 553 Date- 13.3.91



Comments.

1. Reel/orange weak fluorescence.

2. Orangey fluorescence.

3. Darker than 2, but similar hue.

4. Bright white.

Type.

Results.

Stainint

Sheet no


Sample no. WA14 Accession no. 564 Date. 13.3.91


Surface.Red broken pigment layer.

Stratigraphy.

Red crystalline pigment layer over white ground.

Examination Mounted



Photography: Film Type Mag.no. Film nos.Ektachrome 64 xlOO/x2OO

Comments.

1. Red pigment layer. Crystalline. Uneven and broken in some

areas.

2. White crystalline material-loose matrix.

3. Large red particle of pigment ?

4. Blue amorphous crystalline particle.

Sheet no


UV Source

Sample no. WA14 Accession no. 5 g 4 Date. 13.3.91


Photography: Film Type. Mag.no. Film nos.2|C 3|C 3{C j(C

Comments.

1. Pigment layer does not appear to fluoresce, however there

appears to be a light white fluorescence above it. Possibly

something to do with the mounting medium as there is no layer

visible.

2. Bright white with orange tinge.

Staining

Type.

Results.


An investigation into the use ofsolvent gelsfor the removal ofwax-based coatings on WallPaintings.

Tobit Curteis

Samplenos. WAI-WAI 4

County. London

Village/Town.

London

Name of Building.

Westminster Abbey

Chapter House.


English Heritage.

(Mr Jan Keevil)

Permission granted. 2 1.1.91

Date. 2 3.1.91

Accession nos. 501-504 560-564


South arcade,

central bay.

Dimensions of Painting.

14 3cm. x 2 28cm.

Subject.

Apocalypse of St. John.

Attribution & Date.Between 13 72 and 1404.

Sampledby. Tobit Curteis.


Date. 1806/36 1901/3 1929 1985

Conservator. G.G.Scott A.H.Church H.M.G. English Heritage.

Method

employed.

No exact account

survives, but it

appears that the

paintings were

Varnished during

this period.

Baryta water was

possibly applied

to certain areas

of the paintings

including the area

examined for this

project. No record

of any surface

coating applied at

this time.

Beeswax with

2% linseed oil

was applied to

the paintings &,

driven in with

heat. Used as

adhesive and

Consolident.

IMS 80 %/Propan-2-

ol 80% mixture was

used to surface

clean the

paintings in the

NW arcade. All

other paintings

were surface

cleaned with hot

air and cotton

wool to remove

part of the wax

coating.

Area

TreatedAH Paintings ?Unknown All paintings All paintings.

Location of

records.CIA/EH

CIA/EH EH EH.

Previous

samples

& location.

NoneBritish

Museum. NoneNone

Sheet no.2


Apparent i. stone substrate. 2. White ground 3. In many areas there

stratigraphy. also appears to be a red ground. 4. Paint layers (very

complex and confused in some areas.) 5. Dark resinous

layer. 6. Soft waxy layer.

Possible

technique.Organic medium of some sort (Oil?).

General

condition.Bad exfoliation and decohesion in many areas. Stone

support is often in v.bad condition resulting in surface

damage. Some areas appear to be sound.

Appearance & Organic coatings cover the whole painting. Apparently twodistribution iayers. Possibly thinned in the 1985 conservation by EH.or sorisccs

. Much of the paint surface is consolidated by the surface

coaings. coating as it appears to have lost original cohesion.Coating has collected in all damages or lacunae.

White/green fluorescence over most of coating. Some

repaints appear to show in areas of the hands and face of

figures. Two coatings not apparent in UV.

examination.

Position of

samples.All cross sections were taken from the area of the two

vscrolls' in the hand of the right hand angel. Two coating

samples taken from large lacunae nearby.

Possible anomalies

of area sampled.The very disrupted nature of the surface/coatings and

the varying staratigraphy of the paint layers may make

comparison of individual samples difficult. In most

cases the surface coatings in which we are interested

will be apparent.

Photography:

(type & area)

All areas were recorded with Ilford FP4 (black &

white) and with Agfachrome CT100, in both general

macro.

and

Comments.

Samples were intended to be as representative of the

area as possible, and comparable with other samples

from the same area. It was found that the

stratigraphy of individual samples varied considerably

within very small areas, presumably due to the damaged

nature of the paint layer. This made cross-referencing

more complex than is normal.

Conservation of Wall Painting Department COURTAULD...

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