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Dissertation for Preventive Conservation MA at Northumbria UniversityOnly time will tell -- The St. Olav Hospital time capsule in Trondheim, Norway

By Victoria Juhlin, 2016-05-06

Module code: VA 0767Tutor: Jean Brown

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ContentsAbstract.................................................................................................................................................4

Acknowledgements...............................................................................................................................5

Introduction...........................................................................................................................................6

Theory...................................................................................................................................................7

The time capsule concept..................................................................................................................7

Examples of time capsules.................................................................................................................7

The Massachusetts State House time capsule...............................................................................7

The Osaka Expo ’70 time capsules...............................................................................................10

Preservation concerns related to time capsule storage...................................................................14

The deterioration of cellulose and paper.....................................................................................14

The capsule container..................................................................................................................16

The lid and seal............................................................................................................................17

The environment surrounding the capsule..................................................................................18

An evaluation of various preventive measures................................................................................20

Buffered paper.............................................................................................................................20

Deacidification.............................................................................................................................20

Disinfestation...............................................................................................................................21

Tests............................................................................................................................................21

Barrier materials..........................................................................................................................21

Passive barriers............................................................................................................................22

Active barriers.............................................................................................................................22

Modified atmospheres................................................................................................................23

Oxygen absorbers........................................................................................................................24

Anoxia and hypoxia......................................................................................................................25

Humidity buffers..........................................................................................................................26

Method................................................................................................................................................30

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The St. Olav Hospital time capsule..................................................................................................30

Capsule location..........................................................................................................................31

Capsule design.............................................................................................................................32

Capsule contents and enclosures................................................................................................35

Results.................................................................................................................................................38

Recommendations...........................................................................................................................38

Discussion........................................................................................................................................40

Conclusion.......................................................................................................................................40

Bibliography.........................................................................................................................................42

Figures.................................................................................................................................................48

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Abstract

A time capsule is a closed cache containing objects intended to provide future generations with information about an event or a moment taking place in present time. This work identifies risk factors that may contribute to accelerated degradation and possible disintegration of time capsules and their contents, and investigates preventive measures that may be applied to mitigate these risks. Two time capsule repositories which are of particular interest to preventive conservation are presented: the Massachusetts State House time capsule and the Osaka Expo ’70 twin capsules. A third – recently initiated – capsule project is also accounted for: the St. Olav Hospital time capsule. The owner of this project, the University Hospital in Trondheim, Norway, has engaged the student as external project advisor on preservation matters. An assessment of the St. Olav Hospital time capsule project is included in this work, together with an evaulation of preventive measures that may be suitable for the capsule and its contents. The results of the student’s research is presented as a list of recommendations.

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Acknowledgements

I would like to express my sincere gratitude to Bob Barclay and Brian Durrans for sharing their knowledge, time and support so generously, to Cecilie Flottorp, Stein Johansen and Åse Riaunet for providing me with the opportunity to embark upon this topic, and to Jean Brown, my tutor and supervisor.

A number of people have been helpful in distributing much needed information: Frank Kroekel, Sven Maaske, Doug Nishimura, Janet Reinhold, Alex Roach, Jerry Shiner, Garry Simm, Jacob Thomas, Jack C. Thompson and Christoph Waller. Thank you.

Last, but not least: Petter. You’re my rock. I could not have made this without you.

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Introduction

Time capsule repositories are surrounded by a number of external threats that may cause considerable damage to the capsule and its contents. Examples of such threats include extremes or fluctuations in temperature and relative humidity, natural disasters, pests and microorganisms, vibrations from nearby infrastructures and atmospheric pollutants. Other issues that are likely to cause concerns are the utilization of unsuitable capsule materials, the use of a poorly crafted capsule structure and the selection of chemically unstable artefacts that are to be stored within the capsule. Equally detrimental is the passing of time and man’s ability to forget. In December 2015, the student was engaged as external advisor to a centennial time capsule project, administrated by staff at the St. Olav’s University Hospital in Trondheim, Norway. The project has provided the student with an opportunity to assist the St. Olav Hospital staff in their preparations and to document the conclusions of her research as part of her studies in preventive conservation.

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TheoryThe time capsule concept

The 2006 edition of Oxford English Dictionary defines a time capsule as «a container used to store for posterity a selection of objects thought to be representative of a particular moment in time.» 1 In Posterity and paradox: some uses of time capsules, Brian Durrans refers to the time capsule as a «discrete body of evidence, either of the past preserved against interference until the present, or of the present similarly preserved for posterity».2 According to William Jarvis, the author of Time capsules: a cultural history, the ancestor to modern-day time capsule rituals can be traced back to ancient foundation deposits or rites such as the laying-down of a cornerstone, the celebration of a lower foundation of a building or a roof topping, the cutting of ribbons or the inaugurations of exhibitions, parks and bridges. These rites have much in common with time capsules from the last two centuries, with one difference: they lack definitely set retrieval dates. Deliberate depositions which are scheduled to be unearthed at a specific date is a relatively recent phenomenon.3

Time capsules can be buried in the ground or enclosed in a wall, a niche, a plinth or a cornerstone, stored on a shelf in a museum or archive, or in a home, or even in space.4 The length of its deposit can last for a week, a month, a year, a century, a millenium or forever. The capsule structure can be custom-built, prefabricated or modified from other containers. Time capsule history has seen an abundance of capsule structures made of a range of materials: safes, small-sized coffins, envelopes, boxes, bottles, cylinders and pipes made out of metals or alloys of metals, plastics, wood, glass, board, paper and textiles which have been laminated, glued, welded, melted, taped, nailed or tied together to form a vessel.

Examples of time capsulesIn this section, two time capsule projects have been selected to illustrate a number of preservation concerns and corresponding preventive approaches as seen in time capsule repositories: the Massachusetts State House time capsule in USA and the Osaka Expo ’70 time capsules in Japan.

The Massachusetts State House time capsuleOn 4th of July 1795, to mark the early construction works on the Massachusetts State House and to commemorate the city of Boston and the imminent 20th anniversary of American independence, an enclosure consisting of two lead sheets with curled-up edges was placed beneath a cornerstone of the State House. Within this enclosure were memorabilia dating back as far as 1652. Sixty years 1 Oxford English Dictionary (2006) Time capsule.2 Durrans, B. (1992) Posterity and paradox: some uses of time capsules.3 Jarvis, W. E. (2003) Time capsules: a cultural history.4 NASA (2016) The golden record.

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later, during building repairs, the enclosure was removed and its contents cleaned and documented. Prior to reinterment, preventive measures were taken to ensure the longevity of the encapsulated objects. The original lead covers were replaced with a soldered box. The 18 th century coins were given an acid wash and a coating of beeswax. A few new coins, also treated with beeswax, were added. At the time of its second burial, the capsule contained silver and copper coins (dating from 1652 to 1855), an engraved silver plaque, a copper medal, five folded newspapers, a paper impression of a seal, calling or business cards and a title page from a book. Once the objects were in place, the lid was secured and the capsule reburied beneath the cornerstone.

Figure 1 The Massachusetts State House time capsule

(Photograph © Museum of Fine Arts, Boston, 2015)

In December 2014, the box – hereafter refered to as the Massachusetts State House time capsule - was excavated from its burial site as part of an attempt to repair a nearby water leak. Figure 1 shows the capsule after its retrieval and prior to conservation. A preliminary examination of the capsule using X-Ray Fluorescence revealed that it was made of a (heavily corroded) brass, that its’ lid was sealed with 8 screws and that it contained paper objects and coins. The capsule weight (approximately 4.5 kg) and exterior measurements (14 x 19.1 x 3.8 cm) were registered. To facilitate the opening of the capsule, the screws holding its lid in place were loosenen and some of the corroded lead solder was removed. This process took several hours.5

5 Museum of Fine Arts Boston (2015) See contents revealed.

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In January 2015, the capsule was opened before public by Pamela Hatchfield, Head of Objects Conservation at the Museum of Fine Arts, Boston. The overall condition of the encapsulated objects was very good. The limited space within the capsule meant there was very little room for excess oxygen which can contribute to oxidation. There were no signs of mould growth, possibly due to the presence of copper which is a good fungicide. Directly below the capsule lid were the newspapers, stacked on top of eachother. Apart from some minor discolouration caused by corrosion products, lead-contamination and slight curling of the edges, they were in excellent condition - likely due to the high-quality rag paper. Figure 2 shows some of the newspapers in a still folded state. Beneath the newspaper were the coins and the medal. The acid-treated 18 th-century coins and the medal were affected by superficial corrosion. At the bottom of the capsule, interleaved by two very acidid sheets of lining paper, was the silver plate. The direct contact with the acidic papers had caused some discolouration of the silver surface. The coated surfaces of the calling or business cards had been disrupted by crystals of lead salt.6

Figure 2 The folded newspapers

(Photograph © Museum of Fine Arts, Boston, 2015)

Following a month-long exhibition, it was decided that the Massachusetts State House time capsule together with its contents should be reburied in June, 2015. A series of preventive measures were undertaken to ensure the longevity of the brass capsule and its contents. The coins were cleaned from beeswax and housed in Corrosion Intercept and Static Intercept envelopes, made to size. All objects were interleaved with Whatman Chromatography Paper, which has an alpha cellulose

6 Hatchfield, P. (2016) The Massachusetts State House time capsule.

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content of atleast 98% and a surface pH of 7.4 ± 1 (registered after 16 days of accelerated ageing). 7

The calling or business cards were placed in stable glass enclosures, without direct contact with the glass. The old brass capsule was replaced with a custom-made stainless steel box, which was flushed internally with humidified Argon gas. Once the new capsule was packed, it was placed within a heatsealed package made by RIBS laminated barrier film. The old brass capsule got a similar package. Prior to covering the burial void in the cornerstone, it was lined with polyethylene foam. 8 The email correspondence between Pamela Hatchfield and the student in where Mrs. Hatchfield discusses the conservation and preservations measures is included in Appendix A, together with an information sheet on RIBS. The email correspondence between Frank Kroekel of Corrosion Intercept Technology and the student is seen in Appendix B, and the MSDS for Corrosion Intercept is found in Appendix C.

The Osaka Expo ’70 time capsulesThe Osaka Expo ’70 time capsules consist of two buried capsules – here refered to as capsule 1 and capsule 2 - and two replicas which contain duplicate sets of content. One of the capsules can be seen in Figure 3. The replicas are stored above ground and exhibited for the benefit of the public. A total of 2,098 objects and records are stored in each capsule. The interior of each capsule is divided into 29 compartments. Capsule 1 will remain buried, hopefully undisturbed, until 6970 AD. Capsule 2 - positioned above capsule 1 - acts as a control and preservation audit, and will be unearthed, inspected and reburied once every hundred years.

Figure 3 One of the Osaka Expo ’70 time capsules

(Source: Mainichi Newspapers Co., Ltd. and Panasonic Corporation, 2010.)

7 Pearlstein, E. J., Cabelli, A. King., and Indictor, N.(1982) Effects of eraser treatment on paper.8 Hatchfield, P. (2016) The Massachusetts State House time capsule.

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Capsule 1 and 2 were buried in January 1971, in Osaka Castle Park, at a depth of approximately 14.4 metres and 10 metres below ground level, respectively. The burial depths were not coincidentally chosen.9 At around 10 metres below ground level the earth (or subsoil) is usually insensitive to diurnal and annual fluctuations.10 Regardless of the surface temperature, the ambient temperature at 10 metres below ground will stay a fairly consistant 17° C. Thus, climatic fluctuations and the threat they pose to capsule structures as well as contents may be avoided. The burial place, Osaka Castle Park, was chosen due to its geological stability. In addition, the park rests on land owned by the Japanese government and is listed as a protected site of historical importance. Considerable challenges were faced in the design and construction of the The Osaka Expo ’70 time capsules. The monolithic, spheroid-shaped capsule structure – chosen because of its surface area/capacity ratio and overall stability - must be able to withstand external stress from earthquakes and subsoil movement. Each capsule has a holding capacity of 500 litres and an unladen weight of 1.74 metric tons. The wall thickness range from 35 mm and the top and 70 mm at the base. Each capsule stands on three feet, has three carrying lugs and two lids: one inner and one outer lid.

The material selected for the capsule body needed to meet a series of specific conditions, including immunity to the detrimental effects of humidity, oxygen, atmospheric pollutants and UV radiation, resistance to the dispersion of carbon (which may result in corrosion), and great constitutional strength and high tenacity against external stress. Equally important was the material’s ability to withstand residual welding stress and to remain structurally and chemically stable over a wide range of ambient temperatures. The choice fell on an extremely strong and corrosion-resistant high-grade alloy: an austenitic stainless steel. To avoid the building up of stress within the steel, the capsule bodies were cast. A structural examination using gamma radiation followed suit. As has been mentioned earlier, each capsule interior houses 29 compartments. In order to prevent localized pressure and direct metal-to metal contact between the stainless steel surfaces of the compartments, these were wrapped in aluminosilicate ceramic wool.

The sealing of the capsule bodies posed further challenges. Plastic packing was discarded on the grounds that it is a source of carbon. Metal packing was also rejected, as it can produce intra-crystalline corrosion. Bolts were not an option, due to possible corrosion and metal fatigue. In the end, electrical welding was chosen. Both inner and outer lids were groove-welded, with an electrode similar in chemical composition to that of the stainless steel used in the capsule bodies.

The protective substructures of capsules 1 and 2 were also meticuously planned. The enclosure that protects capsule 1 consist of 7 different layers: the capsule body which is followed by a layer of common silica sand, a hermetically welded casing of stainless steel, a layer of Bentonite (a moisture-absorbent clay with waterproofing qualities) and three concentric layers of reinforced concrete. The enclosure for capsule 2 include the capsule body, a layer of silica sand, a stainless steel casing, a layer of Bentonite but only one layer of reinforced concrete so as to simplify the centennial unearthening process. The complete substructure of capsule 2 is presented in Figure 4. The initial plan of a mutual vault substructure was discarded, as – in the event of a collapse – the rigid vault 9 Panasonic Corporation (2010). Time Capsule Expo ‘70.10 Florides, G. and Kalogirou, S. (2005) Annual ground temperature measurements at various depths.

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construction would subject the time capsules to severe shock. Ultimately, the two capsules were encased separately, buried on concrete rafts and embedded in coarse sand and subsoil. Surrounding the capsules and their concrete rafts are a circular arrangement of auger piles and double soil piles. In time, these will likely collapse and allow the rafts to move independently within their different levels of subsoil.

Figure 4The protective substructure of capsule 2.

(Source: Mainichi Newspapers Co., Ltd. and Panasonic Corporation, 2010.)

Prior to encapsulation, all objects were treated under sterile conditions in a dust-free environment. This was done to prevent mould and bacteria growth. In addition, all objects were sterilized and disinfected. Several sterilization methods were used, such as ethylene oxide gas, radiation and heat. Due to heat vulnerability, most objects were treated with ethylene oxide. Prior to sterilization, the ethylene oxide gas method was tested and it was shown that in most cases the method would not contribute to accelerated deterioration or, in case of a damaging effect, this would be negligible. Already at an early stage of the The Osaka Expo ’70 time capsules project, tests were conducted to establish the expected rate of long-term deterioration on a range of materials and artefacts. Storage techniques were researched, and the inevitable deterioration of some objects was risk assessed. To

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avoid object deterioration from exposure to oxygen and atmospheric pollutants, the capsule air was replaced with argon gas, thus creating an anoxic environment within the capsules.

To further stabilize the interior environment, a large quantity of zeolite scavengers were used as a means of controlling the humidity within the capsule.11 Objects in need of specific levels of humidity were placed in individual enclosures which were conditioned with zeolites, silica gel and/or argon gas, humidified to a desired level.12 Objects that were known to be extremely prone to deterioration but could not be replaced or excluded, were prepared with special care. Synthetic and natural rubber components were sealed in quartz glass tubes to prevent the dispersion of sulphur which is emitted as the rubber breaks down. In order to minimize damage on other objects due to collagen breakdown and acid hydrolysis from the degradation of tannins, leather objects were stored together in a hermetically sealed compartment. Accelerated aging of the Western and Japanese paper objects showed that some degree of browning, loss of strength and decrease in molecular weight were to be expected in all papers, however less so in the papers composed of long and thick fibres. Ultimately, it was accepted that all paper objects would display a certain degree of browning – likely caused by oxidation and hydrolysis - over time, and that little could be done to prevent this. Paper objects likely to display advanced browning over time (for example, modern mass-produced magazines) were printed on white paper using black ink to increase long-term readability. Black-and-white polyester-base microfilm and motion picture films were developed, fixed and then treated with a solution of gold salts. The purpose of this pioneering technique was to replace silver particles with gold, thus preventing oxidation. Paper-based photographs were not subjected to the gold solution due to paper’s ability to absorb water and chemicals. Instead, the photographs were microfilmed and stored in this manner. Conventionally processed colour photographs, which can be expected to show signs of fading within fifty years or less, were reproduced using the dye diffusion transfer method which has a longer life-expectancy. 13 All printed photographs and films were stored in one hermetically sealed compartment.

In March 2000, capsule 1 – the controle – was unearthed for the first time since its burial, and 173 of a total of 2098 objects were examined together with the capsule structure itself. Most objects were in the same condition as when buried – with the exception of some perished bacteria samples and some sprouted plant seeds. The electric appliances that were tested were in working order. Once the inspection was completed, the capsule was re-buried. It is scheduled to be unearthed again in the year 2100.14

11 The specific amount and brand of zeolites is not mentioned.12 The specific brand of silica gel is not mentioned.13 This is confirmed in an email from Douglas Nishimura at the Image Permanence Institute, seen in Appendix D.14 Panasonic Corporation (2010) A Time Capsule Is Opened for the First Time in 30 Years.

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Preservation concerns related to time capsule storageThis section investigates factors that are likely to affect the longevity of a time capsule and its contents: the inherent instability of paper, issues surrounding the construction and sealing of a time capsule, and the effects of the environment in which the capsule is placed.

The deterioration of cellulose and paperThe hygroscopic nature of cellulose allows it to absorb or release moisture to reach balance, equilibrium, with its atmospheric environment. The moisture contents of a paper affect its dimensions, flatness, strength and folding abilities: abilities that are critical to the performance of the paper. In a paper that is subjected to low RH, the cellulose fibres contract and the paper becomes desiccated and brittle. High RH not only allows the fibres to swell: it also assists in promoting chemical degradation such as acid-catalysed hydrolysis. The swelling and shrinking of fibres exposed to fluctuations in RH cause dimensional changes and structural distortion of paper artefacts which can be seen as cockling, flaking and warping. In paper-based photographs, the emulsion can crack. Water that has penetrated into the capsule can also cause leaves to adhere, text to bleed and artefacts to warp or cockle. It can introduce dirt and debris which will assist in creating a favourable environment for pests and moulds. The presence of water also plays an important role in the chemical degradation of paper artefacts.The inherent properties and quality of paper artefacts and their reaction to relative humidity, temperature, radiation and gaseous pollutants can accelerate the rate of deterioration as seen in natural ageing and initiate chemical reactions that affect the molecular composition of the paper. The two principal chemical degradation pathways of paper are acid-catalysed hydrolysis and oxidation. Paper artefacts subjected to these degradation mechanisms tend to weaken structurally due to shortening of the cellulose chain polymer, known as chain scission.15 Staining and yellowing are also common features. In printed photographs, the emulsion softens and become sticky.

Acid-catalysed hydrolysis requires the presence of acids and hydrogen ions (I.e. water). Water is present in the cellulose fibre as free or bound molecules.16 It can also be introduced as moisture from the atmosphere. Acids are primarily introduced to paper from exposure to gaseous pollutants, as by-products formed spontaneously in ageing cellulose, from the raw materials that constitute paper or from the acidic waste of moulds.

Pollutants can be defined as a substance in the atmosphere that has a detrimental effect on the environment or on an artefact. Gaseous pollutants can be introduced to collections as sulphur dioxide, nitrogen dioxide or ozone from the outdoor atmosphere, or as emissions from the indoor environment. The most common gaseous pollutants that are formed indoors and that pose a considerable risk to artefacts are acetic acid, formic acid, acetaldehyde, formaldehyde, hydrogen sulfide, carbonyl sulfide, and ozone. These pollutants are emitted or «off-gassed» from a range of materials and products such as furniture, adhesives, varnishes, solvent-based paints, cleaning

15 Strlic, M. and Kolar, J. (ed.) (2005) Ageing and stabilisation of paper.16 Strlic, M. and Kolar, J. (ed.) (2005) Ageing and stabilisation of paper.

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products and construction materials.17 In The effect of volatile organic compounds and hypoxia on paper degradation, Strlic, Kralj, Cigic, Mozir, de Bruin, Kolar and Cassar investigates the effects of volatile organic compounds (one group of indoor-generated gaseous pollutants) on degradation of cellulose in a modified environment – a setting similar to that of a time capsule.18 Tests performed by the authors show that removal of volatile organic compounds from the immediate proximity of moderately acidic paper and paper containing lignin has a positive effect on durability. Results from tests performed on deacidified papers indicate that the presence of certain compounds have a considerable negative effect on the degradation process.

Gaseous pollutants are also formed within collections materials themselves. In paper artefacts, acidic by-products such as acetic acid, formic acid and oxalic acid are formed spontaneously as the cellulose degrades. Reactions of the acidic by-products with water that is present in the cellulose fibre results in localized acid-catalysed hydrolysis, which, in turn, catalyzes further degradation reactions. The acidic emissions from the deteriorating paper are, in turn, readily absorbed by nearby paper artefacts, that were originally considered stable.19 Thus, a deteriorating paper can contaminate the entire contents of a time capsule.

Another way that acids can be introduced to paper is from the raw materials used in the manufacturing of paper; especially lignin. Modern machine-made papers usually contain wood fibres, mineral particles (talc, kaolin or calcium carbonate), natural or synthetic sizing agents (starch, rosin or alkenyl succinic anhydride), colourants and water.20 The fibrous material or pulp used in machine-made papers consists primarily of cellulose with the addition of hemicellulose and lignin: three structural elements found in the cell walls of plants, trees and bark. The cellulose polymer which has a high degree of crystallinity is more inert than the amorphous hemicellulose and lignin polymers.21 Lignin in particular is very reactive and can promote acid-catalysed hydrolysis of the cellulose. Lignin can also cause discolouration in paper due to its sensitivity to gaseous pollutants.22

90 % of the printing paper that is manufactured today is produced from mechanical or chemical pulps.23 In the mechanical pulping process, grinding and crushing mechanisms separates the wood chips into short fibres which are turned into pulp. This process does not remove any lignin. In chemical pulping, the wood chips are cooked in order to dissolve lignin. As the pulping proceeds, the lignin becomes more resistant to dissolving while the cellulose becomes more vulnerable to the chemicals. Therefore, the process is stopped before all lignin has been dissolved. Most of the remaining lignin is removed by bleaching.

17 Grzywacz, C. M. (2006) Monitoring for gaseous pollutants in museum environments.18 Strlic, M., Kralj Cigic, I., Mozir, A., de Bruin, G., Kolar, J. and Cassar, M. (2011) The effect of volatile organic compounds and hypoxia on paper degradation.19 Shahani, C. J. and Harrison, G. (2014) Spontaneous formation of acids in the natural aging of paper.20 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.21 Daniels, V. (2007) Paper.22 Brown, J. (2012) Causes of deterioration intrinsic to paper.23 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.

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Biological degradation or biodeterioration agents can also assist in introducing acids to paper. Moulds, a frequent cause of concern in collections, prefer organic materials as their source of nutrition. As they grow, moulds produce enzymes which causes molecular cleaving in cellulose. The mould metabolism also produce acidic waste, which will contribute to further degradation – acid-catalysed hydrolysis - of paper artefacts.24

Oxidative degradation of cellulose is primarily induced by oxygen and light, heat, bleaches from the manufacturing process and/or gaseous pollutants. The presence of small quantities of iron and copper metal salts from the manufacturing equipment of paper can also contribute to the degradation process.25 Interaction between oxidation and acid-catalysed hydrolysis is common. As the cellulose polymer oxidises, the rate of hydrolysis increases due to the introduction of side groups. Furthermore, the oxidation process contributes to raising the concentration of acid in the paper. The interaction between acid-catalysed hydrolysis and oxidation is discussed further in Paper aging and degradation: recent findings and research methods by M.C. Area and H. Cheradame.26

The capsule containerA time capsule container should possess three essential qualities: it should be structurally strong, well-sealed and chemically stable. A compromise on these qualities is likely to affect the longevity of both capsule and contents.

Metals or alloys of metals are recurring materials used in the construction of time capsules. In the 19th century, copper and tin-plated steel were popular capsule materials.27 When the caustic fluxes used in soldering came in contact with moisture trapped within the capsule, copper and steel materials alike were subject to corrosion. Accelerated corrosion of the joints was induced by the presence of moisture and salts, and the formation of electric cells: the latter a result of metal-on-metal contact. Lead, as used in the original Massachusetts State House time capsule, tends to be stable in a controlled environment. However, if lead is in contact with organic acids or acidic by-products of cellulose degradation, corrosion products are formed which can cause considerable damage to nearby artefacts.28 If handled or ingested, lead can cause lead poisoning. Today, most prefabricated time capsules are made of stainless steels or aluminium. Stainless steels are iron-based alloys with a chromium-rich oxide surface film which is formed spontaneously in the presence of oxygen and enhanced by industrial processes. The level of chromium present in the stainless steel is in direct correlation with its resistance to corrosion. If the surface of a high-grade stainless steel is scratched, the oxide film is likely to reform and prevent corrosion from forming. Low-grade stainless steels which contain more carbon may be more sensitive to surface corrosion. Aluminium and alloys of aluminium also forms a self-regenerating surface film which provide some protection against corrosion - as long as ambient RH is below 70% and the air free from dust, salts

24 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.25 Priest, D. (2012) Paper science.26 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.27 Barclay, R. (1995) Time capsules.28 Selwyn, L. (2004) Metals and corrosion: a handbook for the conservation professional.

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and pollutants. Unlike stainless steels aluminium has a high thermal conductivity and should therefor not be welded shut as this may damage the artefacts within the capsule.

The use of plastic containers as time capsules is debatable. Little is known of the long-term stability of plastic polymers under burial conditions. What is known is that all plastics (including natural and synthetic rubbers) deteriorate differently at varying, and unpredictable, rates. Degradation of plastics can alter the composition, properties and the appearance of the material. Ageing plastics can emit gaseous pollutants which leaves the surface of the plastic dry and cracked, or sticky, and which may cause accelerated degradation in other materials. Other physical signs of deterioration include loss of strength, brittleness, colour change and changes in size. The reaction of plastics with oxygen, water, light, heat, ozone and/or metals can lead to chemical degradation of the plastic polymer. Oxidation often occurs in plastics. As the oxygen diffuses into the plastic, a chain reaction takes place which continues until no more polymers remain. Although the oxidation process can take place under ambient temperatures and in the absence of light, additional heat and light energy may accelerate the process. Sufficiently high temperatures can bring about thermal degradation of the plastic, where the physical, chemical and electrical properties of the plastic is reduced. A plastic which has had its chemical structure changed by degradation is more likely to have a heightened sensitivity to water and temperature.29

The lid and sealA structure is only as reliable as its weakest spot, which - in the case of time capsules – is often found in the lid area or the seal. Time capsules can be sealed by a number of methods, by threaded or screw-on caps with a metal gasket or an O-ring, wing nuts, soft soldering or welding. Threaded or screw-on caps are often present in prefabricated capsules, but can be costly to produce if a custom-made capsule is preferred. Corroded screws can prevent an easy opening of the time capsule. More affordable wing nuts can become difficult to unscrew over time due to position and localized pressure. O-ring seals made of thermoset or thermoplastic rubber can decompose over time and allow water, heat and air pollutants to enter the capsule. If the rubber has been vulcanized with sulphur during manufacture, the rubber seal will also emit sulphuric gas as it breaks down.30 Metal gaskets can cause intercrystalline corrosion: local corrosion of the grain boundaries in crystalline structures.31 Soldering joints that have not been executed well can become brittle and crack which, in turn, will allow leaking of air and water. The corrosion of some soldering materials, for example lead, results in structural failure and the migration of corrosion products which is likely to harm the capsule artefacts.32

Welding can be a viable sealing option as long as the thermal conductivity of the metal is low. To avoid overheating of capsule and contents, electric arc welding is preferred to gas flame welding. 33

For additional protection, a layer of glass fibre insulation can be placed between the lid and the

29 Shashoua, Y. (2008) Conservation of plastics.30 Williams, S. (1997) Care of objects made from rubber and plastics.31 Selwyn, L. (2004) Metals and corrosion: a handbook for the conservation professional.32 Selwyn, L. (2004) Metals and corrosion: a handbook for the conservation professional.33 Barclay, R. (1995) Time capsules.

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contents of the capsule. The lid of a welded capsule is opened by mechanical filing. Intergranular corrosion is a concern in stainless steel that has been welded. To avoid this, a welding filler and a stainless steel with a low-carbon content can be used.34

The environment surrounding the capsuleThe PD 5454:2012 Guide for the storage and exhibition of archival materials sets the recommended

ranges of temperature and RH for the storage of mixed archival collections at 13° C to 20° C and 35% RH to 60% RH.35 It has already been established that heat can increase the rate of chemical reactions. At higher levels of RH – 65% and above – mould outbreaks may occur. RH levels of 40% and below can assist in slowing down oxidation and acid-catalysed hydrolysis, however it may also lead to brittleness in paper and glue materials.36

Recommendations on storage conditions for archival collections do not necessary correspond with those of photographic prints. Inkjet prints, for instance, should be stored at a stable point between 30 – 40% RH and 18 – 21 C. Elevated levels of RH and temperature can accelerate the rate of deterioration of photographic prints which may result in bleeding, fading and yellowing of inks. It can also promote mould growth. Fluctuating values of heat and humidity can cause the paper support to warp. As with paper artefacts, photographic prints are very vulnerable to compounds such as sulphur dioxide, nitrogen dioxide, ozone, peroxides and formaldehyde.37

A well-sealed capsule of a sound structure, made with inert materials, may not take damage from being buried or enclosed, nor its contents as long as this has been prepared and packed accordingly. However, if the capsule is buried below ground level its exposure to environmental fluctuations, presence of ground water or subsoil water is a concern. Water may penetrate through deteriorated rubber seams, gaskets or through the structural material itself. It may be introduced as condensation, which, according to Hutton (2004) is «the process when moisture in the air condenses out to form liquid water as fine droplets in the air, or on a relatively colder material ».38 By this definition, even small amounts of water present in fibres can cause condensation to form on the interior walls of a buried or enclosed time capsule. A capsule that has been enclosed within the exterior wall of a building may be threatened by direct penetration of rainwater, rising damp, condensation or hygroscopic salts that can absorb water from the atmosphere, thus increasing the water contents of the wall further. Condensation in buildings occurs mainly in the colder months of the year, when warm, moist indoors air meet a colder wall or window.39 The presence of heat can also be a significant concern. In combination with water, heat can create a suitable environment for pests and moulds which can cause biological degradation in paper

34 Selwyn, L. (2004) Metals and corrosion: a handbook for the conservation professional.35 British Standards Institution (2012) PD 5454:2012 Guide for the storage and exhibition of archival materials.36 Daniels, V. (2007) Paper.37 Fischer, M. (2006) Creating long-lasting inkjet prints.38 Hutton, T. (2004) Condensation. Available at: http://www.buildingconservation.com/39 Ashurst, J. and Ashurst, N. (1988) Practical building conservation: English heritage technical handbook: Vol. 2: Brick, terracotta and earth.

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artefacts. Heat also promotes accelerated chemical degradation in paper. The mechanics behind this process is described in Paper aging and degradation: recent findings and research methods , by M. C. Area and H. Cheradame.40

A capsule placed in a north-facing external wall or cornerstone is spared from extreme fluctuations caused by sun heating. If the capsule is to be enclosed in an internal wall, nearness to radiators, windows, plumbing, technical rooms, kitchens and laundry facilities should be avoided. Most indoor heat sources produce water too: either as an increase in ambient RH or as a direct leak. It is not uncommon that a time capsule and the burial spot or enclosure in which it is placed is provided with additional protection or support of some sort. In the case of the Massachusetts State House time capsule, the void within the cornerstone was lined with polyethylene foam. The Osaka Expo ’70 time capsules are protected by a substructure consisting of layers of silica sand, betonite, additional stainless steel and concrete. The capsule void itself is lined with pillars which will decompose over time and allow the capsules to move in correspondance with the subsoil.

Depending on the conditions surrounding the capsule, a heatsealed barrier film, a water-repellant asphalt- or pitch-impregnated wrapping or a melted wax encasing may suffice. Where structural stress and environmental exposure may be issues, a vault or any other suitable substructure may be needed. In Time Capsules (1995), Barclay proposes the use of a drained brick or concrete vault lined with fibreglass insulation for wall-enclosed time capsules, as seen in Figure 5. This substructure provides protection against environmental fluctuations, penetration of water and corrosion. A protective substructure must not be allowed to rest directly on the capsule as this may degrade the capsule seams over time and allow air or water to reach the capsule interior.41 The emission of gaseous pollutants from fibreglass insulation materials is fairly low, as can be seen in Emisjoner fra byggevarer (SINTEF Byggforsk, 2012).42

40 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.41 Barclay, R. (1995) Time capsules.42 SINTEF Byggforsk (2012) Emisjoner fra byggevarer – Måling i laboratorier og resultater.

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Figure 5A drained brick vault lined with fibreglass insulation.

(Courtesy of R. L. Barclay, Canadian Conservation Institute)

An evaluation of various preventive measuresThis section presents a selection of materials and methods that are often used in the preventive conservation of artefacts in museums, libraries and archives, and that has been evaluated by the student as more or less suitable for the St. Olav Hospital time capsule project.

Buffered paperBuffered papers and tissues contain an alkaline compound which helps neutralise acids that are formed within the material as it ages. The alkaline reserve of the buffered material provides the paper with a surface protection against nearby migrating acids, however it will not stabilize other acidic artifacts. Many artefacts made of paper benefit from storage in buffered folders or boxes. Photographic materials such as colour images, cyanotypes, dye-transfer and albumen prints can be sensitive to alkalines and benefit from unbuffered enclosures.43 This is also true for a number of organic pigments such as gamboge, prussian blue, yellow lake and chrome yellow.44

DeacidificationDeacidification aims to reduce the acidity levels in paper by eliminating hydrogen ions from the paper which will decrease the rate of acid-catalysed hydrolysis. Deacidification can be performed manually with the use of alkaline additives such as calcium, magnesium bicarbonate or calcium hydroxide. Further information on deacidification technologies is found in Deacidification for the conservation and preservation of paper-based works: a review, by Baty, Maitland, Minter, Hubbe and Jordan-Mowery.45

DisinfestationDisinfestation and disinfection/sterilization can be used to protect an object from biological agents. In the Osaka Expo ’70 time capsules, sterilization by ethylene oxide gas, radiation and heat was used. Disinfestation exterminates rodents and insects, while disinfection/sterilization eliminates microorganisms, mainly fungi. Treatment by modified atmospheres is likely to pose a lesser risk to the materials that is treated as well as the personnel and users. Further information on the

43 Northeast Document Conservation Centre (2000) Storage enclosures for photographic materials.44 Ash, N. (1985) Media problems.45 Baty, J. W., Maitland, C. L., Minter, W., Hubbe, M. A., Jordan-Mowery, S. K. (2010) Deacidification for the conservation and preservation of paper-based works: a review.

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treatment methods used in disinfestation and disinfection/sterilization of objects is found in Paper conservation methods: a literature review (Zervous and Alexopoulou, 2015).46

TestsThe Oddy test is an accelerated corrosion test which helps to predict potential emission of gaseous pollutants from artefacts, from surrounding building materials and from enclosures. Oddy tests can be applied to all materials.47 pH tests measure the level of acidity in or on artefacts. It also provides an opportunity to assess the colour fastness of artefacts. pH tests can be performed on the surface of an artefact, using a pH pen or strips, or as destructive cold or hot extraction tests, which measure pH of the entire cross-section of a material.48 In accelerated ageing tests, an aggravated ageing process helps to estimate the chemical stability and physical durability of paper. It also assists in explaining the degradation mechanisms that deteriorate the paper: especially acid-catalysed hydrolysis and oxidation of cellulose, hemicellulose and lignin. In Paper aging and degradation: recent findings and research methods, Area and Cheradame argues that the conditions seen during accelerated ageing tests cause irreversible changes in cellulose that are different from the changes taking place at room temperature during natural ageing. The authors also point out that paper in stacks ages differently than single, loose sheets. The centre of a stack undergo greater deterioration than that of the outer regions: a phenomena which is explained by the confinement of degradation products to the centre of the stack.49

Barrier materialsBarrier materials – beyond ordinary enclosures such as folders and envelopes - are often used as as additional protection for artefacts in storage, exhibition or transit. Some barriers are passive and will resist the transmission of water vapour and emission of gaseous pollutants to various degrees. Others actively adsorb and trap harmful molecules emitted from the artefact itself or from its environment. The detrimental effects of acidic build-ups on an artefact which is stored in a box, displayed in an exhibiton case or encased in a time capsule may be prevented by the use of active barriers.50 Prior to choosing barrier materials, their long-term stability, intended function and expected behaviour when in direct contact with artefacts must be evaluated. A selection of barrier materials used for a variety of purposes in preventive conservation is listed below.

Passive barriersMelinex 516 is a clear, inert polyester terephthalate (PET) film, obtainable in various thicknesses and used in the encapsulation and lamination of artefacts, in conservation treatments and as a dust jacket material for books. Melinex 516 is a passive barrier material which is impervious to water and

46 Zervos, S. and Alexopoulou, I. (2015) Paper conservation methods: a literature review.47 Thickett, D. and Lee, L. R. (2004) Selection of materials for the storage or display of museum objects.48 Thickett, D. and Lee, L. R. (2004) Selection of materials for the storage or display of museum objects.49 Area, M. C. and Cheradame, H. (2011) Paper aging and degradation: recent findings and research methods.50 Shiner, J. (2007) Trends in microclimate control of museum display cases.

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has low permeability to oxygen. It is worth noting that polyester is vulnerable to hydrolysis and that polyester films can create electrostatic charges.51 If the film is in direct contact with friable media, this may transfer to the film.

Marvelseal® is an aluminized polyethylene and nylon barrier foil, which provides a passive barrier to the transmission of water vapour and oxygen as well as emissions from gaseous pollutants. Marvelseal® is a flexible material which can be folded and heat-sealed into bags or attached to the walls of containers for exhibition, storage or transit purposes. It is sometimes used in hypoxia treatments of infested artefacts.52

TYVEK® are spin-bonded, nonwoven, high-density polyethylene fibres, available in a variety of thicknesses and strength. In conservation, TYVEK® is often used as protective wrapping material for artefacts in storage, exhibition and transit, and is thus considered a passive barrier. TYVEK® is resistant to water and dust particle penetration but permeable by gaseous pollutants and water vapour.53 A recent study by Curran, Mozir, Underhill, Gibson, Fearn and Strlic suggest that TYVEK® may have an adverse impact on the degradation of cellulose. 54 Polyethylene plastics such as TYVEK® and Marvelseal® are vulnerable to oxidation and can absorb oily liquids which will cause discolouration and changes in the surface texture of photographic prints.55

Active barriersThe Corrosion Intercept technology provides an active protection of ferrous and non-ferrous metals, alloys of metals, polymers and paper-based photographs against corrosive gases such as atmospheric hydrogen sulfide, carbonyl sulfide and hydrogen chloride. The Corrosion Intercept foil is a three-layered laminated material which consists of a polyethylene core sandwiched by Intercept layers. The core contains highly reactive copper, which assists in forming a preferential corrosion site that creates lasting bonds with corrosive gases. In the process copper is consumed. Direct contact between the foil and the protected object is not necessary. Intercept foil does not contain adhesives or volatile additives, thus it will not contaminate the objects it protects. An additional bonus is that the foil also provide some protection against moulds, possibly due to the copper. According to Nagy, the life expectancy of a 3 mm. Intercept film used indoors is more than 30 years.56

MicroChamber® is a series of archival multi-layered papers and boards that actively absorb and trap chemical species in gaseous pollutants. The product can also be obtained as shredded packing material and as an emulsion which can be used to coat the interiors of exhibition cases, storage

51 Shashoua, Y. (2008) Conservation of plastics.52 Eriksson, T. (2013) Emissioner i slutna utrymmen.53 Conservation by Design Ltd. (2016) TYVEK®.54 Curran, K., Mozir, A., Underhill, M., Gibson, L. T., Fearn, T. and Strlic, M. (2014) Cross-infection effect of polymers of historic and heritage significance on the degradation of a cellulose reference test material.55 Shashoua, Y. (2008) Conservation of plastics.56 Nagy, E. (1999) Corrosion Intercept tent packing and handling system for Donald Judd’s brass and copper sculptures.

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boxes and transport containers. MicroChamber® contains zeolites, activated carbon and alkaline buffers. Zeolites and activated carbon are inert materials with microporous structures. The adsorption of harmful molecules takes place in the structural cavities of both materials. Unlike activated carbon, the cavities in zeolites can be modified to target molecules of a certain size and polarity.57 Another disadvantage with activated carbon is its ability to smudge artefacts that come in direct contact with the material.

The primary purposes of MicroChamber® - that of absorbing by-products of deterioration emitted by the artefact itself while preventing gexternal gaseous pollutants from reaching the artefact – is analyzed further in Microchamber papers used as a preventive conservation material by Hollinger.58

In an email conversation between Conservation Resources International Ltd., distributor of MicroChamber®, and the student, sales representative Shaun Flinders recommend the use of MicroChamber® shreddies in the St. Olav Hospital time capsule. This conversation can be seen in Appendix E.

Modified atmospheresA modified storage atmosphere is an atmosphere in which gas concentrations and levels of temperature and humidity have been manipulated in order to meet specifications. 59 The interior atmosphere of a time capsule can be altered with a combination of absorbing and buffering materials, and the near or complete removal of oxygen which is exchanged with argon, nitrogen or carbon dioxide. The performance of any modification tools are of course dependant on the structural stability of the capsule and the abilities and restrictions of the modifiers that are used.

In 2013, the Preventive conservation team at the Bodleian Library set up an anoxia treatment system for the eradication of insects. The staff used oxygen absorbers and additional desiccants which were placed in a sealed container together with oxygen monitors and the test materials. Humidity readings revealed that the system generated a very high RH within the container. In order to establish which variable had this effect on the system, the absorbers and desiccants were removed gradually. By the end of the third test, the staff discovered that the source behind the elevated RH came from water released into the container atmosphere by the oxygen absorbers.60

Oxygen absorbersOxygen absorbers, also known as oxygen scavengers, antioxidants, interceptors and controllers, originate from the food and pharmaceutical industries. In conservation, oxygen absorbers are often used to eradicate insects and to create an oxygen-starved storage atmosphere, which helps to mitigate oxidation degradation of artefacts. Oxygen absorbers are generally distributed as sachets which contain an agent: a chemical or a combination of reactive compounds such as non-toxic moist iron rust or hydrated iron oxide powder, a moisture binder and water. When in contact with the

57 Rempel, S. (1996) Zeolite molecular traps and their use in preventive conservation58 Hollinger, W. K. Jr. (1994) Microchamber papers used as a preventive conservation material.59 Roach, A. (2016) Time Capsules.60 Bodleian Libraries (2013) Anoxia trial.

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oxygen in a well-sealed bag, storage box, exhibition case or time capsule, the reactive agent will combine with and absorb the oxygen in what is effectively a complete corrosion of the iron. The presence of water within the sachet accelerates the reaction. The water that is not used up in the process will be released into the environment as vapour, which will result in an increase of RH. This can be countered by using humidity buffers. Sachets containing iron powder do not emit any gaseous pollutants and are therefore safe to use with a range of organic and inorganic artefacts.61

The absorption process of oxygen absorbers is oxidative by nature and can be compared with the complete corrosion of iron, where the iron absorbs oxygen. It is also an exothermic reaction. According to Maekawa and Elert, oxygen absorbers can become warm or even hot if they are stacked together and exposed to air for several minutes. In direct contact with artefacts, heated absorbers can cause considerable damage.62

The oxygen absorber AGELESS® contains a powdered mixture of iron, potassium chloride, water and zeolite, which absorbs water and other small molecules selectively.63 AGELESS® can be purchased in sachets of varying sizes. Each size is capable of absorbing a specific amount of oxygen measured in cubic centimetres. AGELESS® can be stored in room temperature, as long as the sachets are not in direct contact with the ambient environment. According to the manufacturer, Mitsubishi Gas Chemical, the correct use of AGELESS® in a sealed container will lower the concentration of oxygen to 0.1% or less. 64 What remains is mostly nitrogen, which is an inert gas. If AGELESS® is exposed to RH levels well below 50% for several months, the reaction process of the absorber will slow down to a possible halt.65 According to Mitsubishi Gas Chemical, AGELESS® can be used in combination with nitrogen anoxia or hypoxia. However, the combination of oxygen absorber and oxygen-starved atmosphere will slower the rate of oxygen uptake due to an initially low concentration of oxygen. The producer does not recommend the use of carbon dioxide or combinations of carbon dioxide and nitrogen together with AGELESS®, as carbon dioxide will inhibit the absorption process. 66

RP Systems® (or Revolutionary Preservation Systems) is a two-component absorber consisting of a sacheted agent and a multi-layered barrier film which is sold as tubes on roll or as ready-made bags. A RP Systems® information document distributed by Sven Maaske of M.Art.Preserving - the European distributor of RP products - is found in Appendix F. As seen in AGELESS®, RP sachets come in various sizes. However, unlike AGELESS® the different oxygen-absorbing capacities of RP Systems® are indicated as the volume of air in the container which will be used, not by the amount of oxygen which is present in the container.

Of particular interest to storage of paper artefacts is the RP-K system®, which absorbs oxygen and atmospheric compounds such as hydrogen sulphide, sulphur dioxide, hydrogen chloride and

61 Maekawa, S. and Elert, K. (2003) The use of oxygen-free environments in the control of museum insect pests.62 Maekawa, S. and Elert, K. (2003) The use of oxygen-free environments in the control of museum insect pests.63 Selwitz, C. and Maekawa, S. (1998) Inert gases in the control of museum insect pests.64 Mitsubishi Gas Chemical (2011) AGELESS®.65 Maekawa, S. and Elert, K. (2003) The use of oxygen-free environments in the control of museum insect pests.66 Mitsubishi Gas Chemical (2011) AGELESS®.

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ammonia. Other systems also absorb water, which can be useful in storage of metals artefacts. 67 Three variations on the barrier films exist: ESCAL Neo™, PTS and aluminium foil. The ESCAL Neo film has a very low permeability to oxygen and moisture, however the information leaflet from the manufacturer, Mitsubishi Gas Company, does not specify its permeability to gases.68 In an email exchange with the European distributor of RP Systems®, the student is recommended to use the aluminium foil as this is particularly suitable for long-term storage as seen in the St. Olav Hospital time capsule.69 To function as intended, the RP sachets and the artefact are placed within a barrier bag made of one of the above films. The bag is then heat-sealed. Small imperfections in the sealing of the bag may have a negative influence on the long-term performance of the absorber.70 To avoid direct contact between the artefact and the absorber, the former can be placed in a paper enclosure. According to Maekawa and Elert the RP agent does not generate heat to the same extent as AGELESS®, thus an enclosure may not be needed.71 If a humidity buffer is to be used, this would need to be placed within the barrier bag too.72 The suitability of RP Systems® is further verified in an email conversation between the student and Jerry Shiner of KEEPSAFE Microclimate Systems; a retailer of RP Systems® and AGELESS®. In this correspondece, Mr. Shiner established that RP Systems® products are more stable than AGELESS® and designed for long-term museum applications. The email correspondence is found in Appendix G.

Anoxia and hypoxiaBesides using oxygen absorbers, an anoxic (oxygen-free) and hypoxic (near oxygen-free) time capsule microclimate can also be achieved by displacing the oxygen with dry nitrogen or argon gas. Nitrogen MSDS is found in Appendix H, and argon MSDS is found in Appendix I. The displacement of oxygen is done just prior to closing and sealing the capsule. It is absolutely essential that a time capsule which has been flushed with gas is completely sealed. If not, the negative pressure produced by the removal of oxygen will cause air, water and atmospheric pollutants to be drawn into the capsule. A detailed description of air-displacing is provided in Time capsules by Barclay.73 Nitrogen or argon gas leaves no chemical residue on artefacts. An oxygen-depleted atmosphere may be helpful in the reduction of oxidative damage, but it is not an universal cure for all modes of deterioration. Some colourants – particularly dyes and pigments used in watercolours – can fade more rapidly in the absence of oxygen. Unlike argon which has the added benefit of preventing biodeterioration by microroganisms, nitrogen is used as a food source by some microorganisms. Consequently, nitrogen anoxia or hypoxia may cause mould growth.74 67 Mitsubishi Gas Chemical (2007) RP Systems®.68 Mitsubishi Gas Chemical (2007) RP Systems™.69 Maaske, S. (2016) Inquiry about ESCAL Neo.70 Brown, J. P. (2010) The Field Museum archaeological metals project: Distributed, in situ microenvironments for the preservation of unstable archaeological metals using Escal barrier film.71 Maekawa, S. and Elert, K. (2003) The Use of Oxygen-Free Environments in the Control of Museum Insect Pests.72 Maekawa, S. and Elert, K. (2003) The Use of Oxygen-Free Environments in the Control of Museum Insect Pests.

73 Barclay, R. (1995) Time capsules.74 The Integrated Pest Management Working Group (2008). Museumpests.net.

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A complete removal of oxygen which causes the capsule interior to dry out can result in brittle paper that may not be possible to handle at the time of unearthing.75 To avoid any risk of «RH shock» in artefacts, the gas can be humidified to a level corresponding with the needs of the artefacts prior to flushing.76 Another option could be to use humidity buffers.

Humidity buffersIn preventive conservation, humidity buffers are primarily used to control and condition the RH of microclimates such as exhibition cases, storage boxes and shipping crates. An example of a time capsule that also contains silica gel is presented in Figure 6. Humidity buffers consist of silica gel, which is a chemically inert and non-toxic material composed of silicon dioxide. The internal network of silicon dioxide consists of interconnecting pores which adsorb or desorb water molecules through capillary action. This process continues until equilibrium with the ambient atmosphere has been reached.77 Due to its infinite life-span, silica gel can be re-conditioned. The market offers many silica gels, and some are discussed below.

Figure 6Cross-section of a time capsule where silica gel has been inserted.

(Courtesy of R. L. Barclay, Canadian Conservation Institute)

75 Barclay, R. (1995) Time capsules.76 Maekawa, S. and Elert, K. (2003) The Use of Oxygen-Free Environments in the Control of Museum Insect Pests.77 Weintraub, S. (2002) Demystifying silica gel.

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RHapid GEL which is developed by Art Preservation Services has a buffering capacity in the 40 – 55% RH range.78 RHapid GEL are distributed in MarvelSeal® sachets and can be purchased pre-conditioned. RHapid GEL MSDS is available upon request from Art Preservation Services, see Appendix J.

ArtSorb, manufactured by Fuji Silysia Chemical Ltd., is obtainable as beads, sheets or cassettes.79 Its adsorption range is 60 – 80% RH, which does not correspond with the PD 5454:2012 recommendations on storage climate for archival collections.80 Furthermore, ArtSorb contains a soluble salt, lithium chloride, which has the potential to induce corrosion to metal objects. The presence of lithium chloride in ArtSorb and its possible harmful effect on artefacts is supported by several sources.81 Fuji Silysia Chemical Ltd. does not provide a material safety data sheet on their website or upon request, however a MSDS from 2002 is available online and included in Appendix K.

PROsorb, another commercially available silica gel, can be obtained as beads, cassettes, sachets or sheets, where the beads and cassettes can be purchased pre-conditioned or not conditioned. On their website, Long life for art has published a list which illustrates the adsorption capacity of PROsorb at 25 C.82 PROsorb consists of 97% silicon dioxide and 3% aluminium oxide and does not contain lithium chloride. Its adsorption range is in accord with the PD 5454:2012 recommendations.83 The beeds generate very small amounts of dust, however according to the European distributor Long life for art, the sheets are not entirely dust-proof.84 The cassettes, which are constructed of polypropylene and a vapour-permeable polyester, are open to air on one side and are designed to lay flat.

The use of humidity buffers is not without potential risks. A concern that needs to be addressed is the adsorption capacity stability of silica gels over an extended time period. According to Long life for art, in the first 20 to 40 years of use the adsorption capacity of silica gels drops to approximately 70% of their original scope.85 In a time capsule that is hermetically sealed, this would mean a steady increase of internal % RH for atleast 20 years. Long life for art estimates that over time, the use of PROsorb can increase the RH of a sealed container with approximately 0.8 to 1% per year, depending on ambient conditions. The information is based on experimental tests lasting over 5 and 10 years.86 Another concern, related to the use of silica gels in exhibition cases, is brought to attention by Buttler in Aspects of the history of the showcase. According to Buttler, stratification can take place if

78 Weintraub, S. (2002) Demystifying silica gel.79 Fuji Silysia Chemical Ldt. (N/K) ArtSorb.80 British Standards Institution (2012) PD 5454:2012 Guide for the storage and exhibition of archival materials.81 Lau, D. (2005) Silica gel and lithium chloride., Waller, C. (2016) ART SORB., Sá, S., Carlyle, L. and Pombo Cardoso, I. (2015) Artsorb® in microclimate frames: Oddy testing to evaluate the corrosive potential of lithium chloride and the efficacy of Tyvek® to mitigate its effects.82 Waller, C. (2016) PROsorb.83 British Standards Institution (2012) PD 5454:2012 Guide for the storage and exhibition of archival materials.84 Waller, C. (2016) PROsorb.85 Waller, C. (2016) PROsorb. [Email]86 Waller, C. (2016) PROsorb. [Email]

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the transfer of moisture between the humidity buffer and its ambient atmosphere is inadequate. 87 In Trends in microclimate control of museum display cases, Shiner points out that the capacity of humidity buffers can be overwhelmed if inadequate amounts of buffer is used or if the container leaks.88

An option to silica gels, especially relevant to time capsules, may be desiccant clays. DESI PAK and CLAYPACK are examples of two desiccant clays which facilitate the use of a natural, non-toxic and moist-absorbing clay, bentonite.89 Both clays can be obtained from Long life for art. DESI PAK and CLAYPACK bentonite is encased in non-woven and dust-proof bags, where some sizes can be re-conditioned for repeated use. On their website, Long life for art provides information on how to calculate the amount of packs needed for a specific volume. Although its buffering capacities are lower than silica gel, bentonite clay may loose adsorption capacity or release moisture into the ambient atmosphere of the capsule interior.90

A second option to silica gel is to let the contents of the St. Olav Hospital time capsule act as a self-buffer. Paper possesses the property of absorbing and giving off moisture until the moisture in the paper and the moisture in the atmosphere are in equilibrium. At various levels of RH, paper holds different percentages of water and will absorb or give up water until it reaches equilibrium with the existing temperature of the room. Thus, the water content of paper which is placed in a sealed container will effectively control the RH of the container, as long as the temperature within the container is stable.91 In Trends in microclimate control of museum display cases by Shiner, the author advocates the self-buffering qualities of some materials, such as paper. According to Shiner, the moisture exchange between the microclimate of a sealed enclosure and its hygroscopic contents can remain balanced.92 In email correspondence between the student and Jacob Thomas, Postdoctoral research fellow at the University of Gothenburg Department of Conservation, Mr. Thomas confirms that paper containing a certain RH level will buffer itself as long as the container is well sealed, the volume of the paper contents is close to that of the container volume and any ambient fluctuations are not of an extreme and lasting nature. This email correspondence is included in Appendix L.

87 Buttler, C. (2007) Aspects of the history of the showcase.88 Shiner, J. (2007) Trends in microclimate control of museum display cases.89 The reader will perhaps remember that bentonite was also used in the substructure of the Osaka Expo ’70 time capsules.90 Waller, C. (2016) PROsorb. [Email]91 Padfield. T. (2006) The interaction of water vapour with paper.92 Shiner, J. (2007) Trends in microclimate control of museum display cases.

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MethodThis section introduces the St. Olav Hospital time capsule. Due to uncertainties regarding the placement of the capsule, its structure and contents, the ensuing evaluations and recommendations may be revised at a later stage in order to meet with the preservation requirements of the finished capsule and its contents.

The St. Olav Hospital time capsuleIn December 2015, the student was approached by staff at the Division of Mental Healthcare, St. Olav University Hospital in Trondheim, Norway (hereafter referred to as St. Olav Hospital). Plans for a new building intended to house the Østmarka psychiatric emergency ward, as seen in Figure 7, were on their way and staff at St. Olav Hospital wanted to document the history of the ward and its current and future functions in the form of a centennial time capsule, filled with paper documents and printed photographs. The student, a paper conservator by profession, was engaged as external project advisor.

Figure 7The ring marks the location of the new Østmarka psychiatric emergency ward in Trondheim.

The current building (as seen in image) was torn down in winter 2015/2016.(Source: The Division of Mental Healthcare, St. Olav University Hospital in Trondheim, 2016.)

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Capsule locationDuring the initial stages of the project, the staff at St. Olav Hospital expressed a wish to enclose the capsule within an interior wall of what is to be the main building of the new Østmarka psychiatric emergency ward. Several positions within the building were suggested as capsule location. Prior to deciding on location, the student asked the staff to consider factors that may contribute to accelerated degradation, such as:

▪ Nearness to technical rooms, toilets, kitchens, laundry facilities, radiators, windows, doors, indoor plumbing, piping, air conditioning systems or other appliances which may generate or spread additional heat and water, fluctuations in climate, pollutants and vibrations.

▪ Security and safety; for the capsule as well as staff, visitors and patients.▪ Method of ensconcement and wall thickness.▪ Logistics and building function.▪ Building materials.

As of May 2016, the likely capsule location – which has been chosen by the Hospital staff – is an internal wall situated in the ground floor vestibule, as seen in Figure 8. The staff felt that this location would ensure that the capsule is well remembered without interfering in the daily routines and the safety of the workplace. The capsule is to be stored horizontally, at a height of about 40 to 50 centimetres above floor level.The wall which may house the time capsule borders to a technical room. The details concerning this room and its purpose are not yet set, however the student has been informed by the building engineers that the room and its contents will generate very little heat.

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Figure 8Detail of Østmarka psychiatric emergency ward, main building.

Capsule location is seen as a red ring, and the entrance to the building is marked by an arrow. The grey area shows the location of the technical room.

(Source: Nordic Office of Architecture © 2016)

The details surrounding the placement of the capsule will be finalized in May 2016: approximately two weeks before the casting of the wall foundations start. The choice of location may be subject to change due to construction limitations or costs. The foyer walls will consist of 10 cm thick steel wall studs, sandwiched by two 15 mm thick oriented strand boards (OSB) and two 13 mm thick gypsum boards. The capsule wall will be thicker in order to accommodate the capsule void. The choice of OSB and insulation materials have not yet been made. The staff wishes to insert the capsule in its finalized position at a, as of now, unknown date in late 2016. By then the building will be ready and most likely in the early stages of use.

Capsule designThe capsule design has been discussed thoroughly by the student and the St. Olav Hospital staff. Three capsule structures have been evaluated: prefabricated, modified or custom-made containers. To the knowledge of the student, no Norwegian manufacturer produces prefabricated time capsules. Therefore, international sources have been assessed. One such example is Future Packaging & Preservation: a company that specializes in prefabricated time capsules which can also

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be custom-made. Their bolted time capsules and capped time capsules come in a variety of sizes, and are made of stainless steel. The opening of the bolted capsule structure has a rim, an o-ring packing and a groove to fit the o-ring. Drilled holes allow for screws to fix the lid in place. Figure 9 illustrates the bolted time capsule. The capped time capsule structure has a silicone seal. This is seen in Figure 10. All capsule structures as seen on the webpage of Future Packaging & Preservation are vertically oriented.93

Figure 9

Bolted time capsule 3000

By Future Packaging & Preservation

(Source: Future Packaging & Preservation

© 2016)

Figure 10

Capped time capsules 4300

By Future Packaging & Preservation

(Source: Future Packaging & Preservation © 2016)

Another company that offers a prefabricated time capsule is Preservation Equipment Ltd.94 The Preservation Equipment capsule is cylindrical, approximately 60 cm long and 22 cm in diameter, 93 Future Packaging & Preservation (2016) http://www.futurepkg.com/94 Preservation Equipment Ltd. (2016) http://www.preservationequipment.com/

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made of an austenitic stainless steel and its lid is sealed with a gasket made of PTFE or Polytetrafluoroethylene. Paper conservators may be familiar with Teflon® and Gore-Tex®: materials fabricated from PTFE. According to Nancy Purinton and Susan Filter, authors of Gore-Tex: an introduction to the material and treatments, Gore-Tex® is an inert, air permeable and hydrophobic material with good ageing qualitites.95

Modified time capsule structures make use of an already excisting vessel that can be adapted to suit the needs of the capsule project. One such example is the Cornelius keg, as seen in Figure 11, which is a stainless steel canister used to store and dispense home-made fizzy drinks and home-brewed beer. A Cornelius keg can be made into a functioning capsule structure provided that the interior tubes are removed. The keg has three openings: a main aperture and two smaller nozzles which can be used to create anoxia or hypoxia. One nozzle allows the gas to be inserted, while the other releases contained air. All three openings have neoprene gasket seals. Cornelius kegs come in a range of different sizes.

Figure 11Cornelius Keg

(Source: Turbosquid © 2014)

95 Purinton, N. And Filter, S. (1992) Gore-Tex: an introduction to the material and treatments.

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The ultimate choice for the St. Olav Hospital time capsule has fallen on a custom-made high-grade stainless steel box of a rectangular shape which is to be produced by a local metals workshop, VerkstedPartner AS. A custom-made capsule may be more expensive and complex to produce, however a number of reasons support this choice:

▪ The long-term stability of high-grade stainless steels provides added insurance against degradation of the capsule and its contents.

▪ High-grade stainless steels have low thermal conductivity, which allows for welding and a hermetically sealed capsule.

▪ The use of a local workshop enables monitoring of the production process and materials selection.

▪ A local workshop can also assist with sealing the capsule safely prior to ensconcing. ▪ A custom-made structure can be crafted according to specific measurements, thus

minimizing object damage due to shortage of space. Additional space within the capsule also accommodates for humidity buffers, absorbers, insulation materials and more.

Capsule contents and enclosuresAs of May 1st, 2016, the list of capsule contents has been reviewed several times. Currently it includes approximately:

400 unbound paper documents of A4 size, stored as gathering 50 printed black and white photographic prints of various sizes

The paper documents will be photocopied on ‘archival’ paper, which is defined as a «Paper of high permanence and high durability» by ISO 11108:1996.96 In order to be considered archival, the paper’s fibre composition, grammage, pH value, alkali reserve, tear resistance, folding endurance and Kappa number must meet with the requirements listed in ISO 1108:1996. 97 The photocopying paper will be purchased from KLUG Conservation. A quality guarantee for this paper is enclosed in Appendix M.

The choice of developing process for the photographic prints requires careful consideration. Due to budget restrictions and practical aspects, the photograps will most likely be produced with a commercial inkjet printer. Inkjet printing came into wide-spread use in the late 1990’s.98 In inkjet printing, the ink is deposited on a fibre-based support to form an image. Continuous flow inkjet

96 International Organization for Standardization (1996). ISO 11108:1996 Information and documentation – archival paper – requirements for permanence and durability.97 International Organization for Standardization (1996). ISO 11108:1996 Information and documentation – archival paper – requirements for permanence and durability.98 Fischer, M. (2006) Creating long-lasting inkjet prints.

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printers use an electrostatic charge which pushes ink out of the nozzle reservoir, whereas drop-on-demand printers only use ink droplets needed to form an image. The combination of a multitude of printers, dyes, pigments and papers generates a vast amount of inkjet print products where some may be more long-lasting than other. Inks used in inkjet printers are dye-based or pigment-based. The small, single molecules of dyes make these more prone to fading, more sensitive to water and humidity and more vulnerable to gaseous pollutants than the larger molecules that constitute pigments. Papers used for inkjet prints come in four cathegories: bond paper, inkjet paper, coated inkjet paper and fine arts paper. Bond paper, often used as photocopying paper in offices, is made of wood pulp and is sized with rosin. It is not suitable for long-term storage due to its lignin content and sizing. Inkjet paper has a slightly better quality than bond paper and contains starch, polymer or pigment sizings that produces a whiter and more ink-receptive surface. Coated inkjet paper contains a surface coating such as silica, clay or titanium dioxide, which aid in receiving the inks. Owing to this coating, the image is of better quality and the inks are more stable and less prone to bleeding. Fine arts paper are made of alpha cellulose fibres, contain no lignin or rosin sizing and sometimes have the added benefit of an alkaline reserve. They can be purchased as glossy or matte, depending on the desired effect of the image.

The American-based Wilhelm Imaging Research institute conducts accelerated light exposure and dark aging tests to determine the comparative life expectancy of inkjet printed photographs, as well as that of traditional black-and-white and color photographs.99 In 2008, the Institute rated the permanence of five Hahnemühle fine arts papers printed with Epson pigment-based ink on an Epson Stylus printer. According to the ratings (and subject to the right choice of ink and paper and a non-fluctuating storage climate of 22.7 C and 50% RH), the longevity of certain combinations of Hahnemühle fine arts inkjet papers, Epson inks and printers may exceed 200 years.100 Further information on the dark storage stability, water-fastness and humidity-fastness of inkjet prints can be found in An overview of the permanence of inkjet prints compared with traditional color prints by Wilhelm and McCormick-Goodhart.101 In an email correspondence between Garry Simm, UK & Nordic Countries Sales Manager at Hahnemühle and the student, Mr. Simm recommends that the student use Photo Rag paper for the documents as well as the photographic prints in the St. Olav Hospital time capsule. This correspondence is included in Appendix N.

Enclosure structures and materials should be evaluated on criteria such as long-term stability, intended function and behaviour if in direct contact with artefacts. A list of different types of enclosures and their applications is found in PD 5454:2012 Guide for the storage and exhibition of archival materials.102

99 Wilhelm Imaging Research, Inc. (2016) http://www.wilhelm-research.com/index.html .100 Wilhelm Imaging Research, Inc. (2008) Hahnemühle inkjet papers with Epson inks – print permanence ratings.101 Wilhelm, H. And McCormick-Goodhart, M. (2000) An overview of the permanence of inkjet prints compared with traditional color prints.102 British Standards Institution (2012) PD 5454:2012 Guide for the storage and exhibition of archival materials.

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The photocopied documents will be stored as gatherings in expansion portfolios made of paper that corresponds with ISO 11108.103 The portfolios will also be obtained from KLUG, and their quality guarantee is found in Appendix O. Enclosures used in the storage of photographic prints should meet specifications as seen in ISO 18902 Imaging materials – processed imaging materials – albums, framing and storage materials.104 The enclosure materials must also pass the Photographic Activity Test (PAS), which is accounted for in ISO 18916 Imaging materials – processed imaging materials – Photographic activity test for enclosure materials.105 Inkjet prints can be stored in enclosures made of paper or plastics, as long as these materials are selected with care. Polyvinyl chloride (PVC) enclosures should be avoided, due to its chemical instability and inclination to release gaseous pollutants upon ageing. PVC also contains plasticizers – additives used to soften the PVC and reduce its glass transition temperature – which may cause changes in the surface of the inkjet print. Hydrolysed or oxidised cellulose nitrate and cellulose acetate releases nitrogen dioxide and acetic acid respectively, which can assist in acid-catalysed hydrolysis of paper. 106 Polyester, polystyrene, polyethylene and polypropylene plastics are usually considered inert, unplasticized and of good chemical stability.107 As mentioned in a previous section, these plastics also have disadvantages. Polyester is vulnerable to hydrolysis, polyethylene can be sensitive to oxidation and can, like polypropylene, absorb oily liquids which will cause discolouration and surface changes in the artefact.

Factors promoting the use of paper enclosures in the storage of photographic prints include paper’s ability to be labelled using a pencil, and its porous structure which prevents accumulation of moisture and build-up of gaseous pollutants within the enclosure. One possible disadvantage with some paper enclosures such as four-flaps or portfolios are their space-requirements. In the case of the photographic prints, seamless envelopes may therefore be a more space-saving solution. A final choice will be made as soon as the list of contents has been revised and the staff at St. Olav Hospital has gathered the artefacts that are to be stored in the time capsule.

Oddy tests, pH tests and accelerated ageing tests helps to establish the quality and stability of enclosure materials and are very useful tools in preventive conservation. St. Olav Hospital does not offer equipment or facilities for these tests, thus external sources must be relied upon for cooperation. The student is currently in contact with local partner institutions that may be able to assist, depending on costs. The results of Oddy tests and accelerated ageing tests takes up to one month to receive.

103 International Organization for Standardization (1996). ISO 11108 Information and documentation – archival paper – requirements for permanence and durability.104 International Organization for Standardization (2011). ISO 18902 Imaging materials – processed imaging materials – albums, framing and storage materials.105 International Organization for Standardization (2007). ISO 18916 Imaging materials – processed imaging materials – Photographic activity test for enclosure materials.106 McCormick, K. and Schilling, M. R. (2014) Animation cels – preserving a portion of cinematic history.

107 International Organization for Standardization (2011). ISO 18902 Imaging materials – processed imaging materials – albums, framing and storage materials.

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ResultsRecommendationsThe following set of recommendations are intended for the preparations of the St. Olav Hospital time capsule and its contents. The list is not exhaustive nor detailed, as it is likely to change at a later stage of the project due to the uncertain nature of many aspects surrounding the capsule structure, its contents and its location. A revised and final list will also contain recommendations on how to pack the capsule.

As of May 2016, the recommendations for preventive measures concerning the St. Olav Hospital time capsule are as follows:

Take note of the building materials that are used, their readiness to emit gaseous pollutants as well as their moisture contents. This information can help in decisions of a preventive nature, as seen below.

Deposit the capsule within an internal wall, at atleast 40 centimetres above floor level.

Avoid proximity to sources that can generate excessive heat or humidity, or fluctuations thereof.

Depending on the capsule location, a isolated void or a substructure can relieve the capsule from pressure and fluctuations in temperature and RH. If this is not feasible, consider a wrapping or a heat-sealed barrier bag.

Look into the possibility of performing Oddy tests, pH tests and accelerated ageing tests on the materials that will be stored in the capsule. This encludes enclosures.

Evaluate the need for deacidification of the capsule contents.

Assess the stability of the artefacts, and evaluate the need for absorbers, barriers, humidity buffers, desiccant clays and/or other materials and techniques that can assist in creating a suitable microclimate within the capsule.

Consider the benefits and disadvantages with anoxia or hypoxia. Assess costs and long-term performance.

Invest in a custom-made, high-grade stainless steel box-sized capsule, and have it welded to avoid corrosion of the joins.

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Aim for a hermetically sealed capsule. Moisture, air or pollutants allowed to reach the capsule interior can cause considerable damage to the artefacts.

Do not use screws or bolts as these may corrode and dislocate over time.

Avoid the use of plastic materials in the capsule structure, as these are likely to decompose and affect the contents.

Store the capsule in a horizontal position, to avoid crushing and distortion of contents due to gravitation. This is particularly important if the capsule isn’t completely filled.

A plaque, located in direct nearness to the capsule, will assist in remembering the capsule.

A duplicate set of contents and additional information on the capsule project can be deposited at the local city archives.

Registration of the capsule project at the webiste of the International Time Capsule Society may be a further means to secure that the capsule is remembered.

Instead of depositing unstable artefacts that will deteriorate rapidly and cause damage to other materials, consider making photocopies on paper that meets with international standard requirements on archival storage. Photographs can be printed onto a similarly suitable paper. Pay attention to the combination paper/ink/printing device, as this may interfere with the long-term quality of the artefact.

Purchase enclosures of a quality that corresponds with international standards and recommendations. Make sure the size and function of the enclosure is in accordance with the needs of the artefact.

Store photographic prints in separate enclosures of a seamless and glue-free construction.

The student has not listed the need to register the climate that surrounds the capsule location. Long-term measurements can assist in revealing seasonal or sharp fluctuations or excessive temperature or RH: information that is needed to make valid decisions on preventive measures. Nor does the list contain a caution against inserting a capsule in a recently finished building which may still contain high levels of moisture and gaseous pollutants. Unfortunately these factors can not be remedied in the St. Olav hospital time capsule project, for reasons which have been pointed out earlier. The hospital staff has, however, been made aware of the risks surrounding this project.

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DiscussionThe new Østmarka psychiatric emergency ward does not yet exist as a finished construction. Thus it is not possible to evaluate the environment surrounding the likely capsule location. There will be no opportunity to take long-term climate readings of the interior of the building prior to the ensconcing of the capsule. Climate readings taken over atleast one year will assist in discovering possible excesses or fluctuations of temperature and relative humidity generated by the indoor environment as well as the external climate. The exact location in where the capsule is to be ensconced has not yet been decided. The current location – in a vestibule wall which abuts a technical room – is considered less than ideal from a preservation point of view. The details surrounding the use and contents of this room has not been formalized yet, and it is likely that the capsule project will have progressed to a near-finished state by the time the purpose of the room has been completely established and the area put into use. The delays in finalizing the list of contents will also postpone the crafting of the capsule structure as well as decisions on barrier materials, absorbers, buffers and secondary enclosures, where a complete capsule structure is needed in order to calculate suitable amounts.

ConclusionAs this dissertation comes to an end, the student has had time to reflect upon the time capsule concept and its potential as a long-term storage vessel for artefacts intended for future generations. The deposition of a time capsule can be thought of as many things: an experiment, a means of communicating with our future, a joint adventure which helps to bring together the individuals in a group of people or an organisation. The capsule’s role as “a dormant museum” however can be disputed. Too many uncertainties will have direct consequences on its survivability – factors that can be near impossible to calculate. In many cases the materials that is deposited within a time capsule would probably fare better in archives or museums, where they may or may not be forgotten.

The work surrounding the St. Olav Hospital time capsule will continue until later this year, and there will be many opportunities to revise the recommendations that are presented in this work and to explore all areas that have been covered here. Some of the materials and methods that have been presented in this work deserve future investigations. The student would be interested in setting up some comparative experiments with a range of absorbers and humidifiers. Another topic that would be interesting to pursue is the ability of paper to act as a self-buffer.

Preventive conservation is all about buying time. With correctly executed measures, it is often possible to prolong the life-span of a object or a material. In the case of time capsules, verified methods used at the work bench or in the storage depository may not suffice. For most materials, their function after a certain amount of years can only be estimated. Thus, the best solution for the St. Olav hospital time capsule may very well be to take a very basic approach: produce a capsule structure which will provide a hermetical enclosure to its contents, fill it up with artefacts that have been transferred to acid-free, buffered paper and packed in similarly acid-free and buffered folders

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or envelopes, add a considerable amount of active barriers which will absorb gaseous pollutants, seal the lid with welding and ensconce the capsule within an interior wall. Examples such as the Massachusetts State House time capsule show that there is hope for this approach: even in circumstances where the preventive measures of old have caused more damage than the storage conditions themselves. In the case of St. Olav’s Hospital time capsule, the student awaits further decisions on the location of the capsule, its production and contents. She will then put some of her new skills into practice. And after that, only time will tell.

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International Organization for Standardization (2007). ISO 18916 Imaging materials – processed imaging materials – Photographic activity test for enclosure materials. Available at: http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=31940[Accessed May 1 2016].

McCormick, K. and Schilling, M. R. (2014) ‘Animation cels – preserving a portion of cinematic history’. The GCI Newsletter, 29(1). Available at: http://www.getty.edu/conservation/publications_resources/newsletters/pdf/v29n1.pdf[Accessed 2 May 2016].

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Figures

Figure 1 Massachusetts State House Time CapsuleMetalOverall: 14 x 19.1 x 3.8 cm (5 1/2 x 7 1/2 x 1 1/2 in.)Museum of Fine Arts, BostonPhotograph © Museum of Fine Arts, Boston

Figure 2 Opening of the Massachusetts State House time capsuleJanuary 6, 2015Newspapers found in the time capsuleMuseum of Fine Arts, BostonPhotograph © Museum of Fine Arts, Boston

Figure 3 One of the Osaka Expo ’70 time capsulesPhotograph © Mainichi Newspapers Co., Ltd. and Panasonic Corporation, 2010

Figure 4 The protective substructure of capsule 2 Technical drawing © Mainichi Newspapers Co., Ltd and Panasonic Corporation, 2010

Figure 5 A drained brick vault lined with fibreglass insulation.Courtesy of R. L. Barclay, Canadian Conservation Institute

Figure 6 Cross-section of a time capsule where silica gel has been inserted.(Courtesy of R. L. Barclay, Canadian Conservation Institute)

Figure 7. The ring marks the location of the new Østmarka psychiatric emergency ward in Trondheim. The current building (as seen in image) was torn down in winter 2015/2016.(Source: The Division of Mental Healthcare, St. Olav University Hospital in Trondheim, 2016.)

Figure 8 Detail of Østmarka psychiatric emergency ward, main building. Capsule location is seen as a red ring, and the entrance to the building is marked by an arrow. The grey area shows the location of the technical room.(Source: Nordic Office of Architecture © 2016)

Figure 9 Bolted time capsule 3000 by Future Packaging & PreservationSource: Future Packaging & Preservation © 2016www.futurepkg.com

Figure 10 Capped time capsules 4300 by Future Packaging & PreservationSource: Future Packaging & Preservation © 2016www.futurepkg.com

Figure 11 Cornelius Keg(Source: Turbosquid © 2014)

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