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MATERIAL RESPONSE AS A CRITERIA FOR THE APPROACH TO RADIATON

TRETAMENT OF CULTURAL HERITAGE OBJECTS

Irina Pucić1, Katja Kavkler2, Branka Mihaljević11 Ruđer Bošković Institute, Zagreb, Croatia

2 Institute for the Protection of Cultural Heritage of Slovenia, Ljubljana, Slovenia

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RADIATION TREATMENT OF CULTURAL HERITAGE (CH)RADIATION TREATMENT OF CULTURAL HERITAGE (CH)

● ionizing radiation is universal biocide● almost unlimited penetration● disinfestation and decontamination● processing of packed objects● conservation and/or consolidation● relatively low-cost method● simple and safe● no residues● no induced radioactivity

butbut● no protection from recontamination● irreversible effects● CH objects have to be transferred to irradiation facility

is a method of intervention conservation using ionizing radiationis a method of intervention conservation using ionizing radiation

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● γ-radiationγ-radiation is high-energy electromagnetic radiation emitted by a radioactive nuclei;

● irradiation is interaction of radiation with matter i.e. energy transfer;

● energy of gamma radiation used for radiation treatment cannot excite nuclei of atoms of irradiated objects → no secondary no secondary radioactivity is generatedradioactivity is generated;

● high penetration ensures efficacy and reliability of biocide effect.

IONIZING RADIATION AND ABSORBED DOSEIONIZING RADIATION AND ABSORBED DOSE

ABSORBED DOSE, D ABSORBED DOSE, D = energy absorbed by irradiated object SI unit Gy (= J kg-1)Is the most important parameter determining the irradiation outcomeIs the most important parameter determining the irradiation outcomeDose rate, DDose rate, D',', D'D' = DD / t ● depends on radiation field strength that is determined by activity of radiation source, i.e. its decay rate; ● radiation field strength decreases with square of distance from the source;● dose rate can be reduced by shielding.ABSORBED DOSE is in most cases the only parameter that needs to be controlled in ABSORBED DOSE is in most cases the only parameter that needs to be controlled in radiation treatment of CH radiation treatment of CH

Radiation facility staff provides dosimetry and decides on optimal geometry.

The lowest possible dose that provides conservation without The lowest possible dose that provides conservation without unwanted side effects is chosen.unwanted side effects is chosen.

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CH - dedicatedCH - dedicatedARC-NucléArt, Grenoble, France Museum of Central Bohemia, Roztoky, Czech Republic ?

RRADIATIADIATION FACILITIES ON FACILITIES Generally at universities or research institutes (except IRASM)

treat CH objectstreat CH objects● IRASM – Bucharest (Romania)● MITR – Łódź (Poland) ● ENEA – Casaccia (Italy)● RBI-LRCD – Zagreb (Croatia)

Radiation facility at LRCD, RBI

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γ – RADIATION DISINFESTATION AND γ – RADIATION DISINFESTATION AND DECONTAMINATION OF CULTURAL HERITAGEDECONTAMINATION OF CULTURAL HERITAGE

1977 - restoration of Ramses II mummy ● radiation disinfestation in collaboration with Arc-NucleArt Laboratory, Grenoble

● started in 1960's● based on experience in radiation sterilization of food, cosmetics, pharmaceuticlas and medical materials● interrupts biodegradation, simultaneous conservation ● radiation treatment also possible with fast electron beams (LINAC)

Baby mammoth Kroma ● Found in Siberia in 2010 ● Suspected anthrax infection● Treated frozen D = 20 kGy● Arc-NucleArt Laboratory, Grenoble

NATURAL HERITAGENATURAL HERITAGE

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MATERIALS OF CULTURAL HERITAGE OBJECTSMATERIALS OF CULTURAL HERITAGE OBJECTS

Major constituents - 2 types of natural polymers cellulosecellulose and various proteinsproteins

● leatherleather● parchmentparchment● wool wool ● furfur● silk silk

● ivory● bone● mother of pearl

synthetic polymers:● viscose● cellulose-acetate ● polyesters ● rubber

● glass ● gemstones● minerals

in polychromy:● pigments● coatings, varnishes ● binding agents● gypsum etc,

other materials on CH objects:

● wood wood ● paper paper ● cotton cotton ● linen linen ● hemp hemp ● natural rope yarns natural rope yarns

composites:inorganics:

● amber

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Biodeteriorating agentsBiodeteriorating agents: insects, fungi, molds, bacteriainsects, fungi, molds, bacteria ● feed on materials of CH objects● produce enzymesenzymes (cellulases, proteases) that may

remain active even if the original agent is removed● thrive in humid conditions

cause chemical changes like● changes in oxidation state● reduction of degree of polymerization● decomposition of molecular structure

that a result in● change in appearance (discoloration, staining) ● loss of mechanical strength● partial or total decomposition

IMPACT OF BIODETERIORATING AGENTS IMPACT OF BIODETERIORATING AGENTS

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1 Gy

dose dose DD

1 kGy 1 MGy

25 kGy25 kGy sterility

disinsection

color changeradiolysis

polymerizationdegradation

fungicide fungicide effect effect

bactericide effectbactericide effect

Radiation treatment - Radiation treatment - dose rangedose range

ffumigation with gases umigation with gases (ethylene-oxide, sulphuryl-(ethylene-oxide, sulphuryl-fluoride)fluoride)

● toxic and/or dangerous - for environment, restorers, curators, even to visitors - legal restrictions

● significant residuals ● low reliability – penetration

depth uncertain, insects may produce barriers, effect on eggs uncertain

● expensive, particularly for large objects

● ethylene-oxide treated object become more prone to reinfestation

anoxic treatment (inert gases) anoxic treatment (inert gases) ● low reliability - insects may produce

barriers, uncertain effect on eggs●difficult for large objects

REMOVAL OF BIODETERIORATING AGENTSREMOVAL OF BIODETERIORATING AGENTS REMOVAL OF BIODETERIORATING AGENTSREMOVAL OF BIODETERIORATING AGENTS

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● ionization and excitation of atoms and molecules● breaking of chemical bonds ● formation of unsaturated bonds (›C=C‹)● oxidation● crosslinking

RADIATION INDUCED CHEMICAL REACTIONSRADIATION INDUCED CHEMICAL REACTIONS

ABAB+ + e-

AB+ + e-

A• + B•AB*

many natural polymers prone to radiation degradation butbut effects of biodegrading agents are similar

cellulosecellulosefungi digest cellulose, release enzymes● decrease of polymerization degree● loss of mechanical strength● release of metabolites

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PAPERPAPER

● processed cellulose fibersprocessed cellulose fibers● mostly wood pulp cellulose – lignin residues ● cotton (textile) or grass cellulose● Standard Whatman paper – pure cellulose, no lignin paper from libraries, archives, museums ● slowly degrades on aging ● predominately attacked by fungi ● fungi present danger to people working with

infected paper● early treatment in 1960's - needlessly high doses, up to 100 kGy → degradation → opposition to radiation treatment● coincided with increasing fumigation

D = 9 kGyD = 9 kGy is enough to destroy most biodegrading agents● negligible changes in physical, chemical and mechanical properties● more pronounced changes observed on accelerated aging● synergism of accelerated aging and irradiation effects, butbut ● accelerated aging effects are different from those of natural aging

for complete fungi removal D=18 kGy but

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PAPER - TESTING THE RADIATION EFFECTSPAPER - TESTING THE RADIATION EFFECTS

ongoing investigations of effects of aging and recurrent attack of biodegrading agents effects on irradiated paper● paper and ink endurance● variability of paper properties – impossible to identify radiation side effects at treatment doses (Moise et al 2012) ● testing dose range has to be at least double than needed for conservation● Area et al (2012) – no detectable change in several kinds of paper irradiated to 11 kGy at various dose rates

problem of standard paper - Whatman degradation already at 5 kGy alternatively permanent lignin-free paper or paper for photo-copying

effect of artificial aging are not the same as of natural aging

10 kGy

mechanical properties folding endurance – indicator of changes in polymerization degree

chemical properties on irradiationoxidation – carboxyl and/or carbonyl groups insigificant concentration below D=10 kGy

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RADIATION TREATMENT OF PAPER RADIATION TREATMENT OF PAPER

radiation treatment irreplaceable despite limitationsradiation treatment irreplaceable despite limitations in cases of● high extent of contamination● biologic attack transferred from wood to paper● information on the paper is more important than paper itself● other collections have to be protected from possible

contamination transfer● catastrophe, especially floodingcatastrophe, especially flooding● wallpaper

to achieve disinsection/disinfection and to protect minimal doses should be appliedminimal doses should be applied

● up to 0.5 kGy for insectsup to 0.5 kGy for insects● up to 9 kGy for fungiup to 9 kGy for fungi

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WOODWOOD

Wood composition● 41- 43 % celluolose● 20 -30 % hemicellulose● 23 - 27 % lignin● resins, lipid acids and steroles lignin

● cellulose fibriles in lignin matrixcellulose fibriles in lignin matrix● lignin "protects" cellulose from radiationlignin "protects" cellulose from radiation

insects attack dry wood

fungi attack wet wood

damaged wood is more sensitive to further biodeterioration

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RADIATION TREATED WOODRADIATION TREATED WOOD

dose dependence of thermal and mechanical properties ● almost unchanged up to D=100 kGy, ● might improve up to D= 50 kGy, probably as a result of crosslinking of

resins● radiation stability tested for almost any kind of wood● radiation treatment can be repeated if needed

high penetration of γ-radiation – ideal for big objects

modul of elasticity (Populus Tremuloides)crystallinity degree of celulosis (Picea Abies)compressibility perpendicular to the fibers (Fagus Orientalis) compressibility perpendicular to the fibers (Picea Orientalis) bending resistance (Picea Abies)

10 kGy

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Protein collagencollagen● properties of leatherleather determined by distribution, orientation and consistency of its fibers. ● its structure stable up to D=50 kGy.● leather tanning – tannin and collagen crosslinking

LEATHER, PARCHMENTLEATHER, PARCHMENT

leather jacket from romanian etnographic collection, D=10 kGy

10 kGy

parchmentparchment - untanned skin – still can withstand radiation dose needed for disinfectionNunes et al (2012) tested parchment samples from archives of University of Coimbra, found no significant decrease in mechanical and optical properties up to 30 kGy.

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Increasingly common in CH collections, can be attacked by fungiChemical characteristics of a particular polymer determine its radiation Chemical characteristics of a particular polymer determine its radiation outcomeoutcome

Romanian film archive

carrier: cellulose-acetate, polyesterbinder: gelatin – attacked by fungi

dosestested D=25 kGy, 50 kGy applied D=25 kGy

● 10% crosslinking● no change in perforation spacing● no free radicals could be detected after 7 days ● no change in color in any layer, even on accelerated aging 6h at 75 ºC

SYNTHETIC POLYMERSSYNTHETIC POLYMERS

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FIBER AND TEXTILESFIBER AND TEXTILES●group of materials very common in CH collections●proteins: wool, silk - fiber of animal fiber of animal originorigin - stable to radiation and can be can be treated for almost any level of treated for almost any level of contaminationcontamination.●cellulose: flax (linen), cotton - fiber of vegetal origin – radiation sensitive radiation sensitive ●synthetic fibers: modified cellulose viscose most sensitive●fungi, enzymatic attack

10 kGy

D / kGy

Testing of model samples - SEM micrographs

LINENLeft: unirradiated Right: irradiated to 120 kGy

WOOLLeft: unirradiated Right: irradiated to 120 kGy

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POLYCHROMY – PIGMENTS AND ADDITIVES POLYCHROMY – PIGMENTS AND ADDITIVES Numerous studies confirmed that changes in pigment properties in dose of CH treatment are negligible or transient● detected by instruments ● not visible to human eye ● exceptions: marble white, chalk and chalk grounding

10 kGy

● dose rate effectdose rate effect observed for chromium-yellow and minium - higher dose-rate = greater changes; ● changes were greater in absence of varnish ● flax-seed oil and gumi- arabic somewhat more sensitive

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pigment 6 kGy 10 kGy 25 kGy

black 5 5 4-5

azure 5 5 4-5

Yellow ochre 5 5 4-5

mars red 5 5 5

light brown 5 5 5

gray 5 5 5

RADIATION TREATED PAINTING - PIGMENTS RADIATION TREATED PAINTING - PIGMENTS

Peru: Leonardo Flores “Sacred Family with Angels”

17th century

● contaminated with fungi ● irradiated on two separate occasions ● D = 6 kGy ● after 6 years D = 9 kGy● no change of materials or pigments were observed

color comparison scale1 = major change5 = no change

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RADIATION EFFECTS IN SOME OTHER MATERIALSRADIATION EFFECTS IN SOME OTHER MATERIALS

10 kGy

Transparent gems - Transparent gems - significant changes in color

even at D=1 kGy!

10 kGy

Opaque gems -Opaque gems - insignificant changes in color at D=10 kGy

Various ornaments on CH objects have very different radiation sensitivity Horn, bone, ivory, tine -Horn, bone, ivory, tine -

observable changes in color appear bellow D=10 kGy

Marble, porcelain, mother of Marble, porcelain, mother of pearl -pearl - significant changes in

color bellow D=10 kGy

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MATERIAL disinsection(0.5 - 2 kGy)

fungi(

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RADIATION CONSOLIDATIONRADIATION CONSOLIDATIONIrradiation of porous material (dry wood, leather etc.) after impregnating the object with a radiation curable resin

● highly efficient butbut● irreversible justified ifjustified if

it is a last chance for very degraded object

the function of the object has to be preserved - flooring

a complex method that requires specialized equipment and facilityLa Martha, before after

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dry wood

X

MMA – only partially fills the structure

UP resin – completely fills the structure

drying

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RADIATION CONSOLIDATION – AN OUTLINERADIATION CONSOLIDATION – AN OUTLINEwaterlogged wood

collapsed structure

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RADIATION TREATMENT OF CH OBJECTS AND ETHICAL RADIATION TREATMENT OF CH OBJECTS AND ETHICAL CRITERIACRITERIA

● JUSTIFIED: - universal biocide that simultaneously acts on all biodeteriorants in every stage of life cycle; - simple, inexpensive non-material and contact-free method- high reliability

● OPTIMIZED:- biocide effect depends on a single parameter that is easy to control, absorbed dose;- fast

● EFFICIENT:- penetrates the whole volume of the object and its packaging, simultaneous treatment possible;- temperature can be selected, radiation sensitivity of biodeteriorants can be increased by heating, frozen objects can be treated;

● LIMITED:- - no visible and/or measurable changes in almost any organic no visible and/or measurable changes in almost any organic material in absorbed dose range for disinfection/disinsection;material in absorbed dose range for disinfection/disinsection; - irradiated objects do not become radioactive;- - poses no danger for restorers, curators, visitors nor the poses no danger for restorers, curators, visitors nor the environmentenvironment.

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Thank you for your attentionThank you for your attention

Ivory Triptych, Trogir catedral, irradiated at LRCD

Slide 1Slide 2Slide 3Radijacijski uređaji posvećeni isključivo konzervaciji predmeta kulturne baštineSlide 5Biodeterioracija predmeta kulturne baštine organskog porijeklaPosljedice biodeterioracije baštinskih predmetaSlide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Utjecaj zračenja na fizikalnu razgradnju tekstilaSlide 18Slide 19Slide 20Slide 21Slide 22Slide 23Svojstva i prednosti radijacijskog postupkaSlide 25