Caroline (Carrie) Roberts presented an interesting talk about a multi-year collaborative project that demonstrates the real impact that surveys and technical studies can have on collections. In less than two years, the authors were able to survey a collection of 200 limestone stelae, assign treatment priorities, identify the agents of deterioration, suggest environmental guidelines, carry out treatments, and develop an informed treatment protocol.
The project began with the survey of the collection of limestone stelae by then 3rd year intern LeeAnn Barnes Gordon and continued as part of Carrie Roberts’ fellowship project at the Kelsey Museum. LeeAnn and Carrie collaborated with scientists in analytical laboratories at the University of Michigan and at the Detroit institute of Arts, including co-author Cathy Selvius DeRoo. Through their hard work and successful collaborations, the authors were able to accomplish an impressive amount and significantly improve the condition and long-term preservation of this invaluable collection.
Carrie first introduced the history of this collection of funerary stelae excavated in 1935 from the Roman-Egyptian site of Terenouthis. You can find some of this info on the Kelsey website here… and here:
She then spoke about the condition issues identified during the survey, which included stone delamination, surface powdering, biological staining, and peeling, darkened coatings. There were several types of salt efflorescence present including spiky salt crystals and more round gypsum like-salts. Spot tests identified chlorides and sulfates. Interestingly, research conducted into the archival holdings of the museum produced some incredibly relevant information regarding the past treatment of the pieces. A transcribed 1941 lecture by the archaeologist indicated that Duco cement was used to stabilize the stelae as they were excavated. The presence of cellulose nitrate was later confirmed using FTIR on samples of the darkened and peeling coatings.
As a result of the survey, approximately ¼ of the collection was determined to be high priority for treatment. These stelae received further study to characterize the deterioration and identify a treatment protocol. Testing was carried out using a barrage of analytical techniques including FTIR, XRF, XRD, specimen culturing and DNA analysis. The results allowed identification of soluble salts (calclacite- a calcium chloride acetate salt produced from interactions with offgasing materials + halide salts), characterization of stone properties (clay component within limestone- possibly responsible for delamination), and ID of the biological growth (black staining identified by DNA as Epicoccum nigrum of the class dothideomycetes, lichen not identified- no DNA present).
The treatment protocol that was developed through testing included:
-Consolidation of the limestone with CaLoSil (150nm particles of lime hydrate Ca(OH)2) in n-propanol. Testing was conducted using CaLoSil, Paraloid B-72, and Conservare (Ethyl silicate) consolidants. CaLoSil was most successful as it reduced powdering after 1 application without darkening stone. It is presumed to penetrate deep into the stone due to the small (nano) particle size.
-Structural stabilization using Paraloid B-72 (in 85:15 ethanol/acetone) injected into delaminating cracks. Not many of the stelae had extensive delamination but Paraloid B-72 was found to successfully stabilize cracks and areas beginning to delaminate.
-Desalination by poulticing with Arbocel paper pulp. This method was considered challenging/problematic and so the environmental controls were considered the best method of preventing future problems from soluble salts
-Coating reduction was accomplished by applying acetone followed by blotting.
-Biological staining was reduced by swabbing with ethanol; however, this was not found to be fully effective.
-Environmental parameters were set based on the equilibrium RH of the identified salts. The recommendation was to stay below 75% humidity, which is the equilibrium of halide salt and below that of calclacite (79%).
Carrie finished with some questions for future research, including: how is the CaLoSil distributed in the limestone after consolidation? What is the nature of the clay component in the limestone? What are the possibilities for reduction of the biological staining? And what is the best method for treating the stelae that had been stabilized with cyclododecane in 2009 when the collection was relocated to the current storage area.
Overall a very informative talk that hopefully will inspire similar in-depth survey and treatment projects!
Tag: archaeology
39th Annual Meeting-OSG, June 1st, Panel Discussion on Ethical Issues in Archaeological Field Conservation
What are the ethical issues that archaeological conservators face in the field? This was the topic of a panel discussion held at the start of the OSG sessions focusing on archaeological conservation. It was organized by the Archaeological Discussion Group co-chairs Claudia Chemello and Susanne Grieve and the OSG program chair Sanchita Balachandran. Four archaeological conservators were invited to talk about some of the issues they face when working on site. The speakers, Angelyn Bass Rivera, Rae Beaubien, Eric Nordgren and Nancy Odegaard, all have different areas of specialization and were able to talk about a broad range of ethical issues that they have encountered in the work that they do.
The first speaker was Angelyn Bass Rivera, a conservator in private practice who specializes in wall paintings and built heritage. She presented 3 case studies and described the issues that she encountered working to preserve hominid track ways at Laetoli , murals at the Mayan site of San Bartolo and at Frijoles Canyon Cataes at Bandelier National Monument. All sites suffered from environmental degradation because they were outdoors, but there also seemed to be larger administrative issues affecting them. Issues such as the need for tourism to a site and its impact in the case of Laeotoli, or the issue of inadequate funding for conservation on archaeological excavations can also affect the preservation of these sites.
Rae Beaubien, archaeological conservator at the Smithsonian’s Museum Conservation Institute (MCI) talked about her experiences working in the field with archaeologists. At sites where there hadn’t been a history of conservation prior to her working there, she was able to come in and establish the protocol for processing finds. She could also forge the idea that archaeologists and conservators should work together from the start. Her work at MCI, where she was able to create an archaeological conservation internship program, allowed her to continue establishing these collaborations and emphasizing their importance in the field.
Rae then went on to discuss some of the items in AIC’s Codes of Ethics that stood out as important to those working in the field. The first was the issue of stewardship and the preservation of collection, where in the field, conservators are responsible for taking care of the entire collection. She then discussed the idea of operating within the expertise of the person charged with doing the work. She felt that in a museum or institution, it was possible to find a specialist or expert for different aspects of conservation or preservation. In the field, however, you are sometimes asked to work outside of your area. Because finding and paying for these specialists or experts is difficult, often the conservator will have to take on additional responsibilities and in those situations, you just do the best you can. Her final point was for those conservators working in the field to be aware of the laws and regulations of each country they work in in regards to antiquities, especially for unprovenanced material. She ended with the idea whether our work in a country brings unwanted attention to a site and once we leave, how do we protect the site.
Leaving the discussion of terrestrial sites, Eric Nordgren, conservator at Queen Anne’s Revenge Shipwreck Project, talked to us about some of the issues conservators of maritime artifacts face, both practical and ethical. In the case of practical, the size of some of the objects brought up from the sea and the size of tanks or equipment needed for their storage and treatment pose a problem. He stressed the importance of long term planning to provide funding and equipment/materials to undertake the conservation and long term preservation of these materials.
In regards to ethical issues, the largest one faced is where artifacts are recovered without following ethical guidelines and work is carried out by treasure hunters or salvage crews. The question is, what do we do about this? Eric’s suggestion is to work with these groups of people, in addition to other professionals involved in maritime archaeology such as boat captains, riggers, etc. to educate them about conservation and have them understand how they can do their work following ethical guidelines. His final point was if we should think about the larger question of whether we even need to excavate these underwater sites anymore and how well can they be documented without excavation.
The final panel speaker was Nancy Odegaard, conservator at the Arizona State Museum, who was asked to speak about her experiences working with human remains. The Arizona State Museum issues permits for excavations and the policy is that if remains are found, the excavation has 48 hours to get someone out there to identify the remains and determine whether they are human. When found, human remains are not excavated in the Southwest. They are not disturbed, unlike in other areas where the remains are exposed, removed and can be sampled/examined/analyzed/reconstructed. She also mentioned that this summer she will be reburying human remains and artifacts that are currently at the museum.
After each speaker presented, the floor was opened for discussion and questions. One of the issues that kept recurring both in the panel presentation and discussion was how to get archaeologists and conservators to work together, particularly in the US. Rae mentioned that in some countries permits and regulations for excavations are centralized so there is common governing body and regulation to guide archaeologists. There are countries that do require archaeologists to work with conservators and having centralized regulations makes enforcing this easier. This is not the case in the US. Rae suggested having conservators go to archaeological conferences to present their research and integrate themselves into archaeology. Training archaeology students about conservation also helps because you get them to understand early in their career about the importance of conservation and working with conservators. Also writing grants to fund conservation on sites from the same sources that archaeologists use and including this as part of the archaeologist’s funding process for their project also helps.
The issue was raised in the question portion about non-conservators treating materials, especially in the case of maritime archaeology. Eric Nordgren had touched upon that in his presentation and addressed this again in the discussion. He brought up the point that often because of the need to recover these types of items and the need for immediate treatment, archaeologists often do the work themselves. The work of non-conservators preserving maritime sites and the issues of working with them was also brought up in paper presented in the OSG session following the luncheon by Susanne Grieve. It seems that the issue of non-conservators treating archaeological materials and how we should deal with them is something that needs further discussion in the specialization of archaeological conservation.
The final point brought up in the discussion session was of conservators working on unprovenanced materials. Museums have protocols for dealing with these, but should conservators have protocols or guidelines on how to deal with these materials. There was not enough time to have a full discussion of this at the luncheon, but it is an important point that was brought up and one I’m sure will be discussed in more depth in the future.
This luncheon introduced us to some of the issues, both ethical and practical, that archaeological conservators face in the field. It also led to discussions about larger issues of funding and allocation of resources for conservation, how to better integrate with archaeologists, working with non-conservators and other professionals and the ethics of dealing with unprovenanced material. Though no clear answers could be given for how to deal with some of these items, it did provide some interesting discussions and reminded everyone about the complexities of conserving material in the field. I think we all left with many issues to think about that certainly should be further discussed in future annual meetings.