Methods of coserving Archeological Material from Underwater Sites- Donny L.Hamilton.pdf

Methods of Conserving Archaeological Material

from Underwater Sites

by Donny L. Hamilton

Revision Number 1

January 1, 1999

Anthropology 605

Conservation of Archaeological Resources I

Nautical Archaeology Program

Department of Anthropology

Texas A&M University

College Station, Texas 77807

Conservation Files

Overview of conservation in archaeology; basic archaeological conservation procedures.

Adhesives and consolidants

Conservation of bone, ivory, teeth, and antler

Conservation of pottery

Conservation of glass

Wood conservation

Leather conservation

Textile conservation

Metal conservation: preliminary steps

Iron conservation: Part I - Introduction and equipment

Iron conservation Part II: Experimental variable and final steps

Non-ferrous metal conservation

Cupreous metal (copper, bronze, brass) conservation

Silver conservation

Lead, tin, and lead alloy conservation

Gold and gold alloy conservation

Casting and molding in conservation

Concluding remarks

Conservation bibliography

The following conservation files were first posted on the World Wide Web during the 1998 spring semester for use by the students

enrolled in ANTH 605, Conservation of Cultural Resources, at Texas A&M University in College Station, Texas. These files constitute

the laboratory manual that is used in conjunction with the course. The emphasis of the course is on the conservation of material from

underwater sites, especially marine sites, but the conservation of material from terrestrial sites is also discussed. While this laboratory

manual is posted for use by students enrolled in the ANTH 605 class, others may download and use the manual; proper credit,

however, must be given. (See the proper citation at the end of this page.)

This laboratory manual has been compiled from material gathered over the past 20 years. It consists of much of the data

presented in a number of publications by the author, as well as class handouts. Particularly important resources include:

1973-1998: Numerous mimeographed class handouts compiled and distributed to the conservation classes taught by the author

at the University of Texas at Austin and Texas A&M University.

1976: Conservation of Metal Objects from Underwater Sites: A Study in Methods . Texas Antiquities Committee Publication No.

1, Austin, Texas.

1996: Basic Methods of Conserving Underwater Archaeological Material Culture . Legacy Resource Management Program, U.S.

Department of Defense, Washington, D.C.

The last publication is largely a compilation of the first two and is very similar in content to this on-line manual. The current

manual does differ from the 1996 publication in that material has been added or updated in some sections. This conservation class

manual changes each time it is used, and new changes and additions are being planned as preparations are made to post this version.

Each time the manual is posted, it will be dated to reflect new changes, and a new revision number will be assigned. Consult the date

and revision number to see if you have the most recent version. Revision 0, dated January 1, 1998, starts the series.

The general reference for the entire conservation manual is as follows:

Donny L. Hamilton

1998. Methods of Conserving Underwater Archaeological Material Culture. Conservation Files: ANTH 605, Conservation of Cultural

Resources I. Nautical Archaeology Program, Texas A&M University, World Wide Web, http://nautarch.tamu.edu/class/ANTH605.

Donny L. Hamilton

Head, Nautical Archaeology Program

Texas A&M University

College Station, Texas 77843-4352

Overview of conservation in archaeology; basic

archaeological conservation procedures

IN THIS FILE:

Basic References

Conservation Ethics

Tenets of Conservation

The Role of Conservation in Marine Archaeology

Basic Conservation Procedures

Field Recommendations

Laboratory Conservation

Storage Prior to Treatment

Evaluation of Conservation Process

Mechanical Cleaning

Treatment to Stabilize

Artifact preservation is one of the most important considerations when planning or implementing any action that will result in the

recovery of material from a marine archaeological site. It is the responsibility of the excavator or salvor to see that material recovered

is properly conserved. The conservation phase is time consuming and expensive, often costing more than the original excavation.

Without conservation, however, most artifacts will perish, and important historic data will be lost. The loss is not just to the excavator

but also to future archaeologists, who may wish to reexamine the material.

Artifacts recovered from a salt water environment are often well preserved but of a very friable nature. In general, artifacts

recovered from anaerobic marine environments (i.e., buried in sediment) are recovered in better condition than artifacts recovered

from aerobic marine environments (i.e., the water column and surface sediment). Artifacts not properly conserved in a timely manner

are apt to deteriorate at a very rapid rate and subsequently become useless as diagnostic or display specimens. Organic material, i.e.,

leather, wood, textile, rope, plant remains, etc., if allowed to dry without conservation treatment, can crumble and become little more

than a pile of dust and debris in a matter of hours. Iron, on the other hand, can last for a few days to months according to the size and

density of the artifact; however, it too will eventually deteriorate and become useless as a display or diagnostic specimen. Bone, glass,

pottery, and similar material will, if not conserved, slowly devitrify and, in extreme cases, degenerate to a pile of worthless slivers. For

these reasons, conservation must be of paramount concern when the excavation of a marine archaeological site is considered.

Before discussing the conservation of archaeological materials, it is helpful to examine and clarify the various definitions of the

term 'artifact.' For the purposes of this manual, the definitions given in the United States Code of Federal Regulations 36, Part 79,

section 4 are applicable (U.S. Department of Interior 1991):

1. Collection: material remains that are excavated or removed during a survey, excavation, or other study of a prehistoric or

historic resource, and associated records that are prepared or assembled in connection with the survey, excavation, or other

study.

1. Material remains: artifacts, objects, specimens, and other physical evidence that is excavated or removed in connection

with efforts to locate, evaluate, document, study, preserve, or recover a prehistoric or historic resource. Classes of material

remains include, but are not limited to:

1. Components of structures and features (such as houses, mills, piers, fortifications, raceways, earthworks, and

mounds);

2. Intact or fragmentary artifacts of human manufacture (such as tools, weapons, pottery, basketry, and textiles);

3. Intact or fragmentary natural objects that are used by humans (such as rock crystals, feathers, and pigments);

4. By-products, waste products or debris resulting from the manufacture or use of man-made or natural materials (such

as slag, dumps, cores, and debitage);

5. Organic material (such as coprolites, and vegetable and animal remains);

6. Human remains (such as bones, teeth, mummified, flesh, burials, and cremations);

7. Components of petroglyphs, pictographs, intaglios, or other works of artistic or symbolic representation;

8. Components of shipwrecks (such as pieces of the ship's hull, rigging, armaments, apparel, tackle, contents, and

cargo);

9. Environmental and chronometric specimens (such as pollen, seeds, wood, shell, bone, charcoal, tree core samples,

soil sediment cores, obsidian, volcanic ash, and baked clay); and

10. Paleontological specimens that are found in direct physical relationship with a prehistoric or historic resource.

This section of definitions goes on to discuss what constitutes associated records resulting from an archaeological excavation.

This manual is concerned only with cultural material or collections resulting from an archaeological excavation; it is does not consider

archival or art collections for which there are established standards of conservation that are quite similar in many ways to the federal

standards established for archaeological material. What is important is that all relevant documentation be recorded from the start,

including all records pertaining to conservation treatment, and that a complete set of records accompany the collection or any artifact

separated from the collection.

The following section discusses alternative methods for conserving archaeological artifacts recovered from marine sites.

Techniques which may only be appropriate for the conservation of artifacts from terrestrial sites will not be discussed. The section is

divided into eight major headings:(1) Introduction to Marine Conservation, (2) Synthetic Resins and Adhesives, (3) Ceramics, (4)

Glass, (5) Bone and Ivory, (6) Wood, (7) Leather, and (8) Metals. Appropriate subdivisions will be found under each major heading.

All the treatments discussed in this manual do not conflict with any known federal regulations and laws; from this perspective,

therefore, there is no limitation on their use.

It is necessary to make a brief statement regarding the level of effort and resources necessary to perform each technique. As each

treatment is discussed, the required chemicals are listed, and any necessary equipment is either listed or obvious. For example, if an

object is to be rinsed in sodium carbonate, it is obvious that sodium carbonate, water, and a vat necessary to hold the object is

required. If the solution and object must be heated during the rinsing process, then a metal vat and a source of heat (i.e., gas stove,

electric hot plate, or oven) is required. There are too many variables involved in each treatment to arrive at any specific cost; the cost

is dependent upon the size of the artifact and the length of time required for treatment, neither of which can be reliably estimated.

How much does it cost to treat by a given treatment a spike from a ship as opposed to a cannon from the same ship? The exercise

merely becomes a numbers game that serves no useful purpose.

Any discussion of both near-term and long-term conservation goals is equally meaningless. In conservation treatments, there are

no near-term goals as opposed to long-term goals; the only ethical alternative is to treat the artifact so that is stable in the

environment in which it is to be stored or displayed. There are some viable alternative conservation treatments for particular artifacts

that can be performed by untrained personnel and with a minimum amount of specialized equipment; these treatments, however, are

employed only when they will successfully preserve the artifact. For the purposes of this manual, near-term conservation goals will be

considered those that deal with the proper storage of an artifact until the long-term goal of suitable treatment can be performed.

Where possible, comments relevant to these two goals will be made. Near-term goals are also most relevant when it comes to making

decisions such as whether an agency wants to contract out the conservation to existing laboratories or establish its own conservation

capability in order to conserve all future artifacts that might be acquired.

BASIC REFERENCES

There is a considerable body of literature on the conservation of archaeological material recovered from all environments, including

that from marine sites. However, in recent years, a significant amount of the available data has been compiled in several publications,

and the majority of the knowledge that is required to conserve artifacts from marine sites can be obtained from a relatively small

number of publications. In addition to this on-line manual, the following publications should be consulted for additional details. These

are the most important publications in the field of marine archaeology conservation to date.

Cronyn, J. M. 1990. The Elements of Archaeological Conservation . Routledge, London.

Grattan, D. W., ed. 1982. Proceedings of the ICOM Waterlogged Wood Working Group Conference .

Waterlogged Wood Working Group, Committee for Conservation, ICOM, Ottowa.

Hamilton, D. L. 1975. Conservation of Metal Objects from Underwater Sites: A Study in Methods .

Texas Antiquities Committee Publication No. 1, Austin, Texas.

_____. 1996. Basic Methods of Conserving Underwater Archaeological Material Culture .

US Department of Defense Legacy Resource Management Program, Washington, DC.

ICOM Waterlogged Wood Working Group Conference. 1985. Waterlogged Wood: Study and

Conservation . Proceedings of the 2nd ICOM Waterlogged Wood Working Group Conference,

Grenoble, France.

Pearson, C., ed. 1987. Conservation of Marine Archaeological Objects . Butterworths, London.

Plenderleith, H. J. and A. E. A. Werner. 1977. The Conservation of Antiquities and Works of Art .

Oxford University Press, Oxford.

These basic references, combined with various articles and papers from the Journal of the American Institute for Conservation ,

the Canadian Conservation Institute, the Getty Conservation Institute, the International Council of Museum Papers, and the

International Institute for Conservation and Artistic Works in London (which publishes Studies in Conservation , the major journal for

conservation), form the core of the information on the conservation of material from marine sites (see bibliography ) . These are

supplemented by various university theses, papers prepared by conservation laboratories that are not widely distributed, personal

communications from conservators, and personal experiences.

The following discussion on conservation is condensed from a combination of the above sources. This discussion, however, cannot

replace consulting these references for a more detailed presentation. A 'cookbook' approach to archaeological conservation should

never be taken. A range of personal experience and a thorough knowledge of the alternative techniques available is required to

contend with the array of material to be treated. Even with this knowledge and experience, there will always be artifacts that simply

cannot be successfully conserved; furthermore, there will always be instances when, for any number of reasons, it is simply not

practical to conserve an artifact.

CONSERVATION ETHICS

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