notes on archeological conservation

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Notes on Archaeological Conservation

Author(s): Carolyn L. RoseReviewed work(s):Source: Bulletin of the American Institute for Conservation of Historic and Artistic Works,Vol. 14, No. 2, Papers Presented at the Second Annual Meeting. American Institute for theConservation of Historic and Artistic Works, Inc. (Apr., 1974), pp. 123-130Published by: The American Institute for Conservation of Historic & Artistic WorksStable URL: http://www.jstor.org/stable/3179329 .

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123Bulletin of the American Institute for Conservation Vol. 14, No. 2 (1974)

NOTESON ARCHAEOLOGICALONSERVATIONCarolyn L. Rose*

While archaeologists realize the importance of usingscientific methods in collecting, analyzing, and correlatingdata, the same systematic methodology has not always been ap-plied to the preservation of their artifacts. Conservation,if employed at all, has too often been postponed for months,sometimes years, after the specimens have been recovered. Thestabilization of newly exposed architectural features on thesite has also been neglected.Granted, most archaeologists are limited by finances,

facilities, and time and few have been trained in "in-field"conservation techniques. The number of archaeological conser-vators is also negligible in comparison to current demand. Norare most museum conservator readily prepared to deal with allof the existing variables which would modify standard conser-vation techniques.However, immediate treatment in the field with properconservation techniques far surpasses any remedial treatmentin the laboratory that waiting would necessitate.At present, there seems to be no alternative but tosystematically approach this problem so that any trained con-servator can grasp the inherent complexities of an archaeolo-gical site.Working with known factors in a pre-defined patternof reasoning can aid the conservator in visualizing the siteand the state of the artifacts. He should then be able to

suggest which conservation techniques would be applicable in agiven location and which would be feasible for the archaeologistat his particular site.It is this correlation between archaeological conser-vation techniques and a particular site which is vital. Cri-tical also is the rapport which must develop between the arch-aeologist and the conservator, so that all conceivable variablescan be accounted for.Whether the conservator himself will be in the field,or whether he must pre-orient the archaeologist in "first-aid"

*Conservator, Anthropology Conservation Laboratory, Smithsonian.


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conservation techniques, this type of correlation through co-operation will prove invaluable.

MethodologyA means of defining the site must first be determined.Realizing that it would be impossible to predetermine all ofthe complex reactions which would have taken place in the soilduring a long period of time, and that there are large gaps ingeological chronology; we are naturally limited in geologicaldata, and must confine our correlations to known factors. Be-

ginning with gross known data and extrapolating to specificswhen possible, fairly accurate assumptions can be made concern-ing the basic conditions of the site. Systems may vary, butmost sites can be broken down as follows:Ecological ZoneAt this point the world can be dividedinto ecological zones determined by theclimatic conditions controlling the in-teraction of organisms. eg. grasslands,tropics, tundra(This information can be obtained fromtexts on climatology and geochemistry)

Micro-environmentThe specific environment in which theartifacts are located can be suppliedby the archaeologist. eg. underwater,cave, hearthSoil Conditions (if applicable)Soil type(s), texture, aeration, min-eral and organic content, pH, etc.(Supplied from texts and the archaeologist)Depending on the origin of the material cultureexcavated, time must be considered separately in determiningif and when homeostasis with the environment has occurred.


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Until many more sites have been studied, time will still be alarge variable. We must therefore rely on previous finds ofmaterial culture in the same time span to determine which typesof artifacts would be representative.By estimating the effect that each of these knownfactors has in promoting physical, chemical, and biologicaldecomposition, one can begin to determine differences in thegeneral states of preservation of organic and inorganic mater-ials at different sites.Using these deductions, the conservator can preparehimself and/or the archaeologist with conservation suppliesbetter suited to the material culture and in quantities re-flecting the number of artifacts to be conserved. By takinginto account the climatic conditions of the area, the conser-vator also will be able to determine which chemical solutionscan best maintain the stability of the specimens which arebeing treated and stored in the field.

ExampleThree sites, one in the sub-Arctic, and two inItaly* have served as examples of this methodology. At theformer site the archaeologist was pre-trained in conservationtechniques by the conservator. In the latter two sites, theconservator pre-oriented himself in applicable conservationtechniques. Site #1 will be detailed with respect to thissystematic approach.

Site #1 (outlined to facilitate correlations)Historical Eskimo Winter House

Eskimo Island, LabradorEcological Zone - Forest-Tundra(extracted from references on climatology)1summerless Arctic regionlong extreme cold wintersannual mean temperature: 300F (-10C)maintains soil moisture in frozen stateuntil late spring

*These two latter sites will be discussed at the annual meeting.


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thawing in first few feet of soilfrozen subsoilsoil seepageprecipitation smallevaporation smallcloud covered areashumid soil and atmosphereMicro-environment (personal communication witharchaeologist)2latitude: 540Nmean winter temperature: 0OF (-180C)mean summer temperature: 500F (100C)house made of turf and peat wallshearth probably present-sea mammal oil fuelartifacts buried in peatapproximate date: 1650"Soil" Conditionsmounds covered with sedges, lichen, mossesunhumidified peat in upper levelshumidified peat in lower levelssurface thawing in summer - saturated surface

The following chart suggests assumptions which canbe made concerning the site. At this point we are dealingwith three separate micro-environments: a permanently frozensubsoil; a freezing and thawing surface layer; and probably ahearth where the burning of oil would have taken place.(See table on following page)From these observations, one can begin to deduce howphysical, chemical, and biological reactions could haveeffected the artifacts while they were buried.

DeductionsOne could deduce that the artifacts recovered fromthe surface layer would be poorly preserved. Expansion andcontraction as the result of freezing and thawing of icecrystals would lead to the disruption of the cellular struc-ture of organic materials. Water movement, biotic activity,and acid conditions during the summer months would have


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PERMANENTLYROZENSUBSOIL SURFACE

Temperature below zero degrees Celsius low to freezing

Water frozen damp to saturate (25frozen (75%)

Oxygen free oxygen may be negligible %higher in cold waterdependent on % usedin biotic activity

pH below 7 below 7mostly organic acids mostly organic acids

Pressure terrestial pressure negligible expansion and contractat this depth as the result of thaand freezingTime3: site dated to approximately 1650 A.D.climatic fluctuation - Two warming periods: one in late 1700'sone in early 1800's


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contributed to further deterioration. The two "warming per-iods" since the seventeenth century may also have influencedan increase in the rate of these reactions.Organic materials should be well preserved in thepermanently frozen subsoil where biotic activity would haveceased. Inorganic materials may still undergo chemical re-actions, but the rate of these reactions will be greately de-creased.The types of chemical reactions which could haveoccurred in the hearth area will depend on the percentage ofoil, peat, and charred material. If specimens were saturatedwith oil, oxidation reactions would be minimized.

Representative artifactsSince the method of excavating the artifacts was tothaw the frozen subsoil layer by layer, one could assume thatall of the specimens would be cold and wet upon recovery.

BoneHydrolysis of the ossein, organic decomposition,and breakdown of the inorganic framework could have occurredon the surface during the summer months. If found, bone wouldbe fragmentary and spongy. Methods of casting impressions,

lifting and impregnating the bone should therefore be discuss-ed. Procedures for cleaning, slowly drying or impregnatingwell preserved bone from the permafrost should be outlined.Wood

Freezing-thawing, water movement, and bioticactivity would have contributed to the deterioration of sur-face finds of wood. Since all recovered pieces would be wet,temporary impregnation with a solution of polyethylene glycolof low molecular weight, was suggested.Tanned skins and textiles

Leather would suffer from reactions similar tothose effecting bone and wood. The extent of deteriorationmay have been minimized by protective tanning agents in theskin, and by slightly acid conditions. It was suggested thatthese specimens be rinsed with water and sealed in polyethyl-ene bags with a fungicide; then reburied to keep them damp and


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cool. The same procedure was mentioned for textiles, whichshould be better preserved if they were protein in origin.Iron

Fortunately iron objects should be in a reducingatmosphere; otherwise even those artifacts buried in the frozensubsoil may be completely mineralized. Special precautionsshould be taken in lifting and packaging the iron; no attemptsshould be made in the field to remove corrosion layers.Specimens were to be rinsed and sealed, wet, in plastics.Several factors concerning the environment must betaken into account in deciding which impregnating and castingmaterials would be applicable at this site. Only impregnatingsolutions which would not be effected by cold temperaturescould be used. The molecular weight of the resins must be lowenough to penetrate well under these conditions. The rate ofchemical reactions such as those involved in casting materialswill be greatly decreased. Humid conditions may also necessi-tate the use of fungicides in packaging specimens.The stabilization of the site was of equal impor-tance. After the artifacts were recovered, it would be nec-essary to refill all of the excavated areas to insure that theintegrity of the structure could be maintained.While suggesting all of the aforementioned procedures,all conceivable variables had to be considered. In additionto those variables previously mentioned were those such astime, money, availability of conservation materials, space,facilities, energy sources, means of transportation, weight,the number of workers; the list could continue.

ConclusionThe problems may seem overwhelming, but those whichwill be solved by preventative conservation measures will far

out-weigh them. Working with the archaeologist in a meth-odology such as this should alleviate many of the unanticipa-ted difficulties in archaeological conservation.Recognizing the variables involved, one realizesthat this is still a preliminary proposal for a method withwhich to approach "in-field" conservation. To avoid such prioranalysis of conditions and material culture, simply because of


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the many variables, is to do nothing to move forward in thisimportant correlation of the site and conservation. As withall attempts in scientific progress, one must begin not bybeing overwhelmed by the problems, but must rather move towardperfecting solutions. This is such a proposal. Unless theconservator at least studies the situation, the archaeologisthas no choice but to continue as before.

WWWWWW ~~~

References1 Arthur N. Strahler, The Earth Sciences (New York, 1963),pp. 218-9, 328-92 William W. Fitzhugh, Associate Curator of Archaeology, TheSmithsonian Institution (personal communication)3 William W. Fitzhugh, Environmental Archeology and CulturalSystems in Hamilton Inlet, Labrador (Washington, D.C.), p.37David Von Endt, Organic Chemist, The Smithsonian Institution(personal communication)Nathaniel Davis, Geo-Chemist, The American University(personal communication)Richard Jordan, Field Director, Smithsonian Institution(personal communication)

notes on archeological conservation

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