Preparing for Conservation on Archaeological Excavations

1. What is the archaeologists role in the conservation process?
2. Do I need a conservator on site?
3. When should I start talking to a conservator about an excavation project?
4. How do I find a conservator to work on site?
5. What conservation supplies do I need in the field?
6. Where can I get conservation supplies?
7. Isn’t conservation expensive?
8. Where will the artifacts go after the fieldwork?

What is the archaeologist’s role in the conservation process?

Too often, archaeologists and conservators can view the archaeologist’s role in the conservation process as packaging up the artifacts to send to the conservator, receiving them at the end of treatment and paying the bill. This is a very simplistic view that ultimately does a disservice to both the artifacts and the site. Although one of the key goals of a conservation treatment is to stabilize an artifact, the other is to elucidate the artifact-to aid in understanding what it was, how it was made and used, how it was deposited and for what reason. This cannot be done effectively or efficiently without the partnership of the archaeologist.

The archaeologist plays a key role in helping to formulate the questions that should be asked and in defining the amount of time that should be spent on understanding each artifact. To truly study and understand an artifact can take a considerable amount of time-time that may not be necessary if the artifact is from a disturbed context or if the construction, use and disposal of that type of artifact are already well understood. Ideally, the conservator and the archaeologist should be in regular contact. At the start of conservation work, the archaeologist should communicate as much information as possible to the conservator about the site, the burial environments and contexts within which artifacts were found, and any methods used to stabilize the artifacts in the field. A dialog should be maintained between the conservator and archaeologists, new discoveries communicated, and new questions formulated and asked.

Key points to remember:

• Provide your conservator with detailed information on contexts (feature descriptions, dates, associated artifacts, soil type).
• Share as much information as you can about the historical uses of the site (topography, drainage, present-day vegetative cover).
• Share information about the appearance of the site as well as any disturbance (rodent burrowing, bio-turbation, tree-root disturbance).
• Clearly identify key research issues developed for your project.

Emphasize and foster communication between sub-consultants. Collaboration between specialists can be highly productive.

Do I need a conservator on site?

The need for a conservator on an archaeological excavation or site varies from project to project. Typically, Phase I (assessment) archaeological excavations do not require the expertise of a conservator in the field. However, Phase II (evaluation) and Phase III (mitigation) excavations may need a conservator to assist in various aspects of the project. Unique finds, heavily corroded or degraded materials, fragile artifacts and particularly waterlogged sites often require the presence of a conservator in the field to help maximize the data recovery potential.

It is not uncommon for a conservator to agree to be “on call” for an archaeological excavation if they are not needed in the field full time. The option of having a conservator on call should be discussed during the planning phase of a project, rather than when a “cool” or fragile artifact is found. Ideally, a conservator should be involved in helping to decide whether their presence is needed. Additionally, the conservator may be willing to help provide input for general object recovery and processing guidelines.

When should I start talking to a conservator about an excavation project?

Ideally, a conservator should be included in the planning stages of an excavation. There are a number of ways in which a conservator may be involved, from providing artifact-handling training to facilitating analysis. In some instances, such as Phase I excavations, surface mitigations, and walking surveys, it may not be necessary to have a conservator in the field full time. It may be preferable to review general handling and object recovery guidelines with a conservator prior to going into the field, and retain the conservator on an “on-call” basis in case of a significant or fragile find. Whatever decision is made, it is important that all parties are aware of it. Communication is key to a successful relationship and will ultimately help to provide greater information about the site
During the planning phase of a project the project archaeologist and conservator should discuss the following points:

1. General site information: How long the excavation will run, where the site is located, what type of site it is, particulars about the field such as pH, soil stratigraphy, features, and the moisture content of the site.
2. The role of the conservator within the archaeological project: Whether or not field visits are necessary and when, how many visits, treatment priorities for artifacts post excavation, the conservation budget for the project.
3. Supplies and equipment that may be useful for the field archaeologists to take on site given the likely nature of the finds and their condition.
4. Recovery and processing techniques that can be used to enhance data retrieval.
5. Recovery and processing techniques that can be used to enhance data recovery.
6. Who will coordinate with the conservator: It is better to have one individual contact the conservator to avoid confusion. This person may be the project leader or someone in the field with general conservation awareness.
7. Other analysts who are likely to be working with the material, what their schedules and needs are.
8. Overall timeline: When should processing be completed, when should treatments be completed, what reports are needed and by when.
9. Where the artifacts will go after excavation: Are they scheduled for an exhibition, study, research or will they go to a curatorial repository, and are there any special requirements as a result of these plans?

How do I find an archaeological conservator?

The American Institute for Conservation (AIC) has a referral service (FAIC) to help people find a conservator. Requests are taken by topic and location. Brochures are also available on how to select a conservator and how to care for objects.

Contact information: American Institute for Conservation
1717 K Street, NW Suite 200
Washington, DC 20006
(202) 452-9545;
info@aic-faic.org http://aic.stanford.edu

The Association of Regional Conservation Centers (508-470-1010) can provide information on 13 regional conservation centers across the country.

Local museums, historical societies, and university departments may also be able to refer you to a conservator. Always ask many Questions of a Conservator to ensure that his or her training and expertise are appropriate for your needs. It is a good idea to get opinions, quotes, and references from at least two conservators.

What conservation supplies do I need in the field?

Supplies most useful in the field are those needed for packaging, padding, and support. Supplies may also be needed for lifting fragile artifacts. Use archival quality materials in the field, as artifacts may be stored in them for long periods.

Coroplast® Boxes	Des: Made of lightweight, corrugated polypropylene/polyethylene copolymer sheets. Uses: A strong box, which won’t collapse when wet. Used for packaging artifacts. Source: University Products; Hollinger; or contact Coroplast for distributors. Note: May require the use of an insert to reinforce the bottom for heavier artifacts. May require polyethylene foam insert to reduce slippery surfaces. Small artifacts (like beads) can get lost in the seams of the box. When wet, corrugations fill with water and cannot be thoroughly dried.
Corrugated Plastic Boards	Des: Corrugated polypropylene/polyethylene copolymer sheet available in several thicknesses (2-6mm). Virgin, translucent, 3mm board is recommended. It is strong and will not cause chemical reactions with artifacts. Also called Coroplast® sheeting. Uses: Use as a flat support with polyethylene foam cushioning. Can also be used to make boxes and trays. Side flaps are easily fastened with polyethylene rivets, tied with cotton twill tape or plastic ties, or adhered using hot melt adhesive. Source: Hollinger; Alexandria Packaging; Cadillac Plastics. Note: When wet, corrugations fill with water and cannot be thoroughly dried.
Cotton gauze/Cheesecloth	Des: Soft, loosely woven fabric. Uses: Wrapping and padding in the field. Source: Fabric stores, grocery stores. Note: Use only when other forms of padding are not available. Do not use for long-term storage of wet materials as mold and fungus will grow quickly. Do not use on rough surfaces as material may catch and pull off surface detail. May leave impressions on soft materials (such as organics).
Ethafoam®	Des: Polyethylene (PE) foam. Specify virgin PE foam, nitrogen blown, not solvent blown. It is available in a variety of densities and thicknesses from 1/32 in. to 4 in. Uses: Thin sheeting used for lining and padding containers for artifact packaging for transport and storage. Thicker planks are used to make individual artifact supports. Foam is easily carved with a knife. Pieces can be glued together with hot melt adhesive or welded with hot air gun. Rough surfaces should be covered with acid-free tissue, Tyvek, or cotton muslin to avoid abrasion of fragile artifacts. Source: Dow Chemical Mfr., Distr. by Alexandria Packaging; Jarrett Industries; University Products; Light Impressions. Buy from a reputable source.
Fasteners, polyethylene	Des: Loops and fasteners. Come in several colors. Uses: Use to attach labels to objects or supports. Source: Hardware stores; Chiswick; Consolidated Plastics. Note: Should never be applied directly to the surface of an object.
Gloves, Latex	Des: Latex gloves in sizes small, medium and large. Choose powder-free. Uses: Handling artifacts and chemical solutions. Source: Fisher Scientific; Lab Safety Supply; Ansell. Note: Some people are allergic to latex-alternatives include nitrile and vinyl gloves. Latex gloves are not impervious to all chemicals and solvents. Check with suppliers to choose the most appropriate glove for your project. Additionally, Ansell has a glove use chart on-line for helping to select the best gloves for each use.
Monel® Staples	Des: Rustproof and chemically resistant staples made primarily of nickel, cobalt and copper. Uses: To attach labels to supports and to staple containers that will hold wet artifacts. Source: Talas; Hardware stores
Nylon-Cotton Gauze	Des: Soft, stretchy bandages, in a variety of widths, stable in a wide range of chemicals. Uses: To hold artifact assemblages together. Source: Medical supply houses; Fisher Scientific. Note: Use only when other forms of padding are not available. Do not use for long-term storage of wet materials as mold and fungus may grow. Will catch on rough surfaces. May leave impressions on soft materials (such as organics).
Nylon-Fiberglass Screening	Des: Inert, black or gray window screen. Uses: Good for packing artifacts for storage in a water solution where diffusion is important. Source: Hardware stores. Note: May leave impressions on the surface of soft materials (such as organics). Rough edges may damage materials.
Open-Cell Foam	Des: Generic form of open-cell foam, usually polyurethane. Sold in sheets and rolls, for carpet underlay, or padded clothing linings. Uses: Open-cell foam can be used to wrap or lay over objects in wet storage for transport padding, and to maintain high RH environment. The foam will hold water, and conform to the surfaces of large objects that you need to keep wet. It will not rot like cotton towels, but is sensitive to ultraviolet light, so keep it out of the sun. Source: Hardware stores, carpet stores. Note: For short-term use only. Will degrade over long exposure to direct sunlight and become sticky and granular. When full of water, foam becomes heavy and will sag and tear easily. Extended exposure to water may cause foam to rot and promote mold growth.
Orthoplast	Des: Quick-set medical casting gauze impregnated with a casting resin. Uses: Hold fragments together when lifting. Source: Pruett Medical Inc.; Johnson & Johnson Orthopedics, Inc. Note: Always use a barrier layer (such as aluminum foil or cling-film) between the Orthoplast and the object. Sets hard and may be difficult to remove from around some objects.
Plaster of Paris	Des: Calcium sulfate hemi-hydrate derived from gypsum. The powder is mixed with water and then sets hard. Uses: Supports for molds and block-lifts. Source: Hardware stores; Construction supply outlets like Lowe’s and Home Depot. Note: Always use a barrier layer (such as aluminum foil or cling-film) between the plaster and the object. Plaster of Paris will not set in contact with damp or wet soils. Heavy when set, adds weight to artifacts, so it may crush fragile artifacts if applied too thickly and may require additional resources to lift. May be difficult to remove from around objects.
Polycarbonate Boxes	Des: Stable, transparent, available in a variety of sizes. Uses: For packaging fragile artifacts for dry storage. Source: Consolidated Plastics Note: Brittle, easily scratched.
Polyethylene Cling Film	Des: Thin food-grade polyethylene film. Sometimes called shrink film. Uses: Barrier layer to prevent plaster, bandages, or other materials from being in direct contact with artifact surfaces. Can be used to hold damp foam around large waterlogged artifacts for transport. Source: Grocery stores (e.g., Glad Wrap); Chiswick. Note: Use the Beilstein test (in the Supplementary materials section) to be sure it is polyethylene, not PVC (poly-vinylchloride) plastic wrap.
Polyethylene Foam	Des: See Ethafoam, See Volara
Polyethylene Sheeting	Des: Chemically stable and water resistant, transparent. Comes in a variety of thicknesses. Uses: Line tanks, seal artifacts, and cover work surfaces. Source: Hardware and building supply stores. Note: Sheeting may become brittle over time and split easily.
Polyethylene Tubs	Des: Watertight, chemically resistant containers. Uses: Storing materials and artifacts. Source: Global; C & H; Consolidated Plastics.
Polyethylene Vials	Des: Low density polyethylene vials with friction-fit, snap closures. Uses: Short or long term storage of small artifacts. Source: Consolidated Plastics; Cole-Parmer.
Polypropylene Containers	Des: Polypropylene containers with tight fitting lids in a variety of sizes. Uses: For packaging small artifacts in liquids or placing in a freezer for stable holding or for creating a stable microenvironment with silica gel. Source: Consolidated Plastics; grocery and hardware stores (e.g. Tupperware®, Rubbermaid®)
Polypropylene Screening	Des: More resistant to chemicals than fiberglass screening. Stiffer than fiberglass screening. Uses: Support artifacts in treatment. Provides more support than regular screening when used in the field. Source: Small Parts, Inc; Companies that supply materials for papermaking. Note: May leave impressions on the surface of soft materials (such as organics). Rough edges may damage materials.
Polyurethane Foam Spray	Des: Available in spray cans as insulation material. Sometimes called expanding polyurethane foam. Uses: Used occasionally for supporting and packing large, fragile pieces for transport. Not for long-term storage. Source: Hardware stores. Note: Newer formulations may not cure completely when used in large quantities; the center remains un-reacted and liquid. Exposure to light causes discoloring and crumbling. Always use a barrier layer (such as aluminum foam or cling film) between the object and the foam. Expansion during curing may exert significant pressure. Components are harmful and should be used with care
Tank liners	Des: Heavy-duty polyethylene and vinyl sheet. Order custom made from tank liner manufacturers. Uses: For lining large storage tanks. Source: Flexi-liner.
Teflon Tape	Des: Strong, chemically inert tape. Comes in rolls, .015″ thick, fits into Dymo Labeler. Uses: Makes embossed labels that are impervious to dirt, stains and most chemicals. Source: Cadillac Plastics; McMaster Carr.
Toweling	Des: Non-dyed terry toweling. Uses: For covering large artifacts to keep surfaces wet. Source: Available from fabric stores in rolls; Testfabrics. Note: For temporary use only-will decay if kept wet for prolonged periods, may cause staining to artifacts. May catch on rough surfaces and cause damage. May leave impressions on softer surfaces (such as organics). Use only when smoother fabric, a storage tank, or water spray are unavailable.
Twill Tape	Des: Woven cotton tape. Soft, good tensile strength. Available in rolls 1/4 to 1 in. wide. Uses: As container and package ties. Source: Benchmark; Talas; University Products; Testfabrics.
Tyvek	Des: Non-woven spun bonded polyethylene sheeting. Use Tyvek with no coatings. Uses: Artifact labels, smooth interface between object and rougher packaging, wrapping which will allow minimal breathing and protect object. Source: Reed Plastics; Cadillac Plastics: Masterpak Note: Can have a highly slippery surface, also can have high static electricity, which can damage fragile textiles.
Tyvek Tape	Des: Non-woven, spun bonded polyethylene backed with acrylic pressure-sensitive adhesive. Uses: Box and tray construction; labels on boxes. Source: Light Impressions; University Products
Volara	Des: Polyethylene foam, closed cell, with a smooth surface. Uses: Provides some support for cushioning artifacts and creating mounts for small artifacts. Source: University Products; Light Impressions; Rubberlite.

These supplies are excerpted from: TECHNICAL UPDATE No. 1 – REVISED 2005 of the STANDARDS AND GUIDELINES FOR ARCHEOLOGICAL INVESTIGATIONS IN MARYLAND, published by the Maryland Historical Trust. The supply list for Technical Update No. 1 is a compilation of collections curation material lists from several sources including: SPNHC (Society for the Preservation of Natural History Collections) pamphlet, CfMA (Council for Maryland Archeology) Collections Curation Committee List of Suppliers.

Where can I order conservation and lab supplies?

There are a number of companies that supply tools, chemicals, resins, and other supplies for conservation. A lot of standard laboratory suppliers also sell suitable materials and tools (usually in bulk, and often cheaper). See the list of suppliers attached to the end of this FAQ.

What conservation supplies do I need in the field?
Storage Materials Suppliers
Where can I get Acryloid B-72 and Acryloid B-67
What supplies are recommended for archival storage of documentation?

Isn’t conservation expensive?

In simple terms, yes. Most conservators in the Mid-Atlantic region will charge $50-$80 per hour for their services on a case-by-case basis (plus materials and special services). See document 1h. What does conservation cost? But consider the cost of conservation in light of the whole archaeological project. U.S. regulations, 36 CFR 79, and the English Heritage planning document Management of Archaeological Projects (1991) both include conservation of the archaeological collection as a requirement or responsibility of the excavator. Neither document sets spending targets, but anecdotally, many projects or archaeological contractors will earmark about 10% of their total budget for conservation.

As in almost any field, there are significant cost savings to be found in pre-project planning. Including a conservator in pre-excavation planning can avoid significant costs associated with emergency procurements, staff and space allocations. Costs for equipment and supplies can be reduced by bulk purchases based on anticipated finds and conservation needs, rather than piece-meal shopping as artifacts are found and shipped off for treatment. Some classes of artifacts, or treatment processes, can be set up for bulk or batch processing, thereby incorporating economies of scale. Finally, long-term contracts for conservation services can incorporate all of these factors to avoid high, piece-work rates.

Such contracts may include the provision for conservation technicians to perform much of the work, thus saving on high labor costs. Project managers should, however, avoid the trap of relying on low-cost student labor without proper trained supervision – “cookbook” conservation performed by inexperienced staff can often lead to far more expensive re-treatment by a trained conservator when the long-term effects of inappropriate treatment affect artifacts in storage.

Where will artifacts go after fieldwork?

This question needs to be answered, and arrangements made, prior to beginning excavation. After fieldwork, artifacts will likely need to be processed further, perhaps at a laboratory, and then will need to be placed in a repository for long-term storage. Many repositories are reaching full capacity, so there is no guarantee that one will accept a collection if prior arrangements have not been made.

The repository should meet professional curation standards. The federal publication: 36CFR§79 Curation of Federally-owned and Administered Archeological Collections, provides information on the requirements for a repository.

Artifacts must be prepared for curation according to current professional practices and the requirements of the selected repository. A repository may refuse collections which do not meet professional standards and guidelines for curation, and which do not originate from the same state as the repository. The principal investigator can consult the collections manager of the repository to obtain a copy of its standards and guidelines, and should become familiar with professional publications about curation, archival practices, and conservation. A collection and its associated records should be kept together to provide access for research and study. Also a collection should not be divided. Most repositories will not accept partial collections from a project, as the research value is diminished.

Sometimes a property owner will insist on keeping the artifacts from a site on their property. The principal investigator should encourage donation of the collection to a suitable repository, so that the artifacts and records can be preserved and accessible for future study. Sometimes there are tax incentives. Otherwise, one can appeal to the owner’s civic responsibility for preserving history, and suggest that donation can provide public recognition in the community.

Before returning artifacts to a property owner, the artifacts should be cataloged, processed, and packaged according to professional standards. Also the artifacts should be thoroughly recorded, photographed and drawn, especially the diagnostic artifacts and other objects critical to the interpretation of the cultural resource. This documentation should be deposited in a repository along with information about the owner(s) and the location of the artifacts. The owners should be given artifact care information and contacts for a repository, in case they or their family wish to the materials in the future.

In summary, include planning for the final disposition of the artifacts before excavation begins. Consult with property owners and the repository ahead of time. If preservation and curation arrangements are established in advance, people are more receptive.

Copyright © 2006 Colleen Brady, Molly Gleeson, Melba Myers, Claire Peachey, Betty Seifert, Howard Wellman, Emily Williams, Lisa Young. All rights reserved. Commercial use or publication of text and graphic images is prohibited. Authors reserve the right to update this information as appropriate.