ANALYSIS AND CONSERVATION OF LEATHER, BONE, AND OTHER ORGANIC MATERIALS
A New Approach to Excavating and Handling Waterlogged Textiles from the American Civil War Submarine the H.L. Hunley. (peer reviewed)
Johanna Rivera and Philippe de Vivies
The Hunley was the worlds’ first successful submarine, sunk in 1984 and found in 1995. Over 1,400 artifacts have been recovered steadily since 2005, including textiles and organics (wood, leather, rope, horn). The inside of the submarine was completely filled with sediment. All crew were found at their stations. The talk involved the textiles on Lt George Dixon, removed in 7 block lifts. The block is placed in a tank and then slowly filled with water. A syringe filled with water is used to dislodge the sediment. Sediments are vacuumed off with a siphon hose made of PVC plastic, controlled by pinching with the fingers. When the need comes to flip it, they fill in gaps with foam, then cover all with a thin plastic film, and then fiberglass (DuraPower Inc Pipe and Hose Repair Kit) and then polyurethane resin. When firm, then they can slide something underneath and flip, exposing the other side for cleaning. Four fabrics were found: a fine black or brown wool, a cotton/wool, a red that turned brown with exposure to UV light, and a strange thread that was all that remained of suspenders that were apparently made of natural latex rubber. Fragments of textile were unfolded underwater, and rounded Mylar patches helped with the manipulation. One textile was a vest, but its stitches that held in the lining were only on the surface, no longer penetrating through the cloth. There is an entire AIC presentation on the vest treatment. Use of a surfactant helped remove dirt from the textile and keep it in solution instead of re-depositing on the textile. There are five more blocks from Dixon to be dealt with, and another 27 textile blocks from the rest of the ship, a huge undertaking. Elizabeth Peacock asks about dye analysis, and says its not likely to be madder, for example, as madder dyed textiles are often better preserved than other textiles in the burial environment.
A Neolithic Shoe from Sipplingen Conservation and Technological Examination
The shoe was found in a burned layer, and thought to be 5000 years old. The material seems to be strips of retted bast fiber, from the lime tree (tilia?) Comparisons were made to other old shoes that had been treated: Feldtkeller (1989) used PEG 400, and consolidated with Luviskol K30 after and then Bojesen-Koefoed et al (1993) using high molecular weight PEG. Seems that for this Sipplingen shoe, 8% PEG 1500 followed by freeze drying was the way to go. Another example about how the conservation field is moving away from the use of low molecular weight PEGs.
Analysis of Plant Fiber Artifacts from a Shipwreck: Application of Material History Methodology
Dr. Chen had a cool chart that was looking at Observation Data, Complementary Data, Supplementary Data, and then Conclusions along the rows, and then the columns were looking at Material, Construction, Function, Provincial, and Value. This was Smith’s Material History Methodology from 1985. Fits nicely with conservation treatment report format, doesn’t it? Dr. Chen was saying it really helps you to be more disciplined and eliminates pre-conceived notions or bias by using a matrix like this. There’s a recent article in the Journal of Nautical Archaeology that is a cordage study (French?) and has a new recommended framework for how to describe cordage. It is tricky to compare cordage if people are not talking about it in the same way. Louis Bartos is a sail maker and historian who was a useful resource. Info about the plant fibers can give you an idea about the size of a ship and the kind of sails it has…looking at the angle of twist, type of weave, seam construction, stitching, etc. I think Dr. Chen felt a little out of place in the context of the other papers, but I thought this was really valuable. With our noses so deep in the science, it is nice to be reminded of the balance we need to have with the interpretation of our wet organics and not just the preservation of our wet organics. Conservators are often called upon to help interpret what we are seeing and it is great to be reminded of some of the work that is happening in that area too. And knowing what people need to look at for interpretation helps guide the aspects of what we need to prioritize for preservation.
Polyethylene Glycol Treatments for Basketry on the Northwest Coast of North America (peer reviewed)
Ellen Carrlee and Dana K. Senge
This was our talk, and I was so glad it was on Friday so I had a chance to ask a lot of people about it before getting up in front of everyone. Despite feeling a little out of our element, Dana and I were definitely on the right track. We were trying to come up with a PEG protocol that would work for basketry. I had two baskets in the lab already treated with 20% PEG 400 and 5% PEG 4000, based on the best knowledge from the late 1990’s, and even though they looked nice, they were too fragile. So I wanted to see if using high molecular weight PEG would help, maybe without low molecular weight, and maybe at higher concentrations. I think that panned out, and is in harmony with the current understanding. Also, my consolidation with Butvar B-98 seems to be something others have found useful. Maybe 55% PEG 3350 is a good way to deal with very deteriorated spruce root. And maybe basketry treatment, which has been very challenging for lots of people, might be best approached with a two-step treatment: step one being PEG and step two being consolidation. I did not get an answer about why my unheated sample treated with 20% PEG 400 and 75 PEG 3350 turned very dark on cycling RH but the heated sample did not get dark. In all cases of treatment with 75%, that was too high and they were excessively brittle. at Dana’s work in compiling old basketry treatment info is right on the money as well, as this kind of data is really useful and she was right to start capturing that, too. We are still missing a bit of the degree of deterioration problem, since Dana and I struggled with what we were seeing under the microscope. I now have this fantasy that I can attract a grad student in wood anatomy to come from Minnesota and work up spruce root and cedar bark for me. If we cover those two materials, we’ve covered most of the baskets on the Northwest Coast? Carlos is keen to try silicone oil on the problem, and maybe I will collaborate with him a bit on that. I have to think it through, since I am feeling like I have a good direction to go with these treatments using techniques that I am comfortable with in terms of reversibility/retreatability, but the idea that giving over a bit of this material for silicone oil might add to our overall big picture knowledge of various tools in our toolbox…hmmm. Tara Grant agreed that POLYOX wasn’t that useful, but in order to work with it they found that putting a pool of it on the table and pushing to object into it was a good way to deal with its lousy handling properties. Kate Singley reports she’s had good luck with Lascaux, although the kinds I tried didn’t work so well for me. Rope gives a similar problem, and was reported on at the Portland WOAM. In Denmark, they tried using Paraloid F-10 on brittle rope after it was PEG treated and that worked well for them. For the consolidation issue, I guess it matters quite a bit whether your consolidant is dealing with the PEG or dealing with the wood. I suspect that if it is the former, then solvent-based consolidants are going to be good (as I was finding) but for the latter when wood is available for bonding (perhaps if the PEG has been cleaned off the surface) maybe that is when people are getting better results with the water-based consolidants. And one final revelation, Dana points out that historical spruce root baskets are BRITTLE too! Chemist Mikkel Christensen from Norway points out to me during one of the breaks that a general rule of thumb is that you can have stability or you can have flexibility but you cannot have both. Don’t miss Dana’s weblog of past basketry treatments and their outcomes at http://waterloggedbasketry.blogspot.com
Assessing the Physical Condition of Waterlogged Archaeological Leather (peer reviewed)
Katerina Malea, Thelxiopi Vogiatzi, David E. Watkinson
To ID the animal species, they used SEM to look at the hair follicle pattern. To assess degree of deterioration they were looking at amino acid analysis of the collagen. In examining leather visually, people tend not to agree in how deteriorated they think it is. pH reflects degree of hydrolytic deterioration. In the 4.6-7.5 range, with most in 5-7 range. They were also looking at shrinkage temperature, and how broad the range was from when the first one went to the last one in heating for shrinkage. Looking at ratio of basic:acidic amino acids? If the ration is low, does that indicate oxidative deterioration? I am not quite catching all the science, it is a little above my head on this talk. Some commentary afterwards cautioned the use of shrinkage temperature as a tool, since it was designed for use on recent leather. Apparently, there’s been some difficulty using it on archaeological leather because of mineralization? It behaves unpredictably? There was a 1997 study that showed a correlation between mineral content and shrinkage temperature. The plot thickens!!
A Comparative Study of Various Impregnation and Drying Methods for Waterlogged Archaeological Leather
Angela Karsten, Kelly Domoney, Liz Goodman, and Helen Ganiaris
There’s a backlog of leather to be treated in the UK, which is a problem because it is prone to mold growth, analysis cannot be completed until it is dry, and it cannot go into a repository wet. Usually, leather from anaerobic terrestrial sites is pre treated with glycerol or PEG and then freeze dried. 20% glycerol gave the best results, and EDTA along with it was good and also helped with flexibility. Using that in conjunction with vacuum freeze drying was the best, and air drying was OK too. All treatments dried darker and somewhat brittle, although the freeze dried ones were easier to examine without damage. The ones that went through controlled air drying with a series of salts to control RH had challenges with mold and using the technique was a pain. If they got some pre-treatment, even 10 years in storage was OK and they didn’t get moldy and good results were still possible. However, without pre treatment they tended to curl up. Ian Godfrey reports that in Australia, they found the glycerol treatments caused dessication and brittleness over time. In the UK, however, it seems that they’ve been using it since the 80’s without that issue, although that’s anecdotal and maybe it needs to be looked into. Dr Godfrey is keen to assist in the analysis of leather and help distribute the results. I think this issue of glycerol is really interesting. Like how the glycerol in the alum treatments for wood seemed to make them much worse? What is up with glycerol? I want to understand it better. Jim Spriggs says they treated leather in York with glycerol and freeze drying since the 1970’s and it does change over time. The ones in York that came out the best were some weird combo of solvent dehydration and then a solvent soluble oil? Wow.
Efficiency and Quality in a Batch Treatment: the Conservation of Over A Hundred Leather Shoes and Fragments
Metal cistern from 1850-1870 contained lots of leather shoes. Used an ultrasonic dental scaler to clean. Removed chlorides in tapwater baths, agitated, up to 3 months long. Iron was removed with either 2% dibasic ammonium citrate as a batch of 50 (immersing them twice) or 5% sodium dithionite in 2% EDA (did I write that down correctly?) used on shoes individually. The latter worked better, but cost more, took longer to prepare, and required ventilation. Iron stains might have helped preserve the collagen? The monitored the color of the solution to know when it was done. When it was rinsing clear, then they treated the leather with PEG, 20% with 1% Hostacor IT since there were metal attachments and wood inserts inside the shoes. She reshaped with foam supports and Supercrinx stretchy self-adhering bandages, and freeze dried for 2 weeks. There was 7-10% shrinkage, and really maybe even a little more than that since they likely shunk a bit in transit. After freeze drying, used some 2% Klucel G in ethanol where needed, and used Lascaux 50:50 498HV to 360HV applied by brush to sheets of Reemay and reactivated with acetone for tear repair. Susanne Grieve mentioned that the Hunley shoes were preserved with commercial shoe inserts successfully. She also likes a material called Bibac plastic, which can be shaped with a hairdryer. Sounds like it has lots of holes in it, so there is less surface area and the leather dries better? Susanne likes Teflon tape during PEG treatment because organic bandages like traditional roller gauze has gotten moldy or has left marks on the surface of artifacts. Emily Williams jumps into the issue of how the term “batch treatment” affects the concept of the artifact value to curators and collection managers. Objects treated individually are perceived as being more precious. But is it chicken and egg? Have the curators and collections managers already made that judgment before the batch treating happened? In the UK at least, with the volume of material and the limits on resources available to deal with it, there is a risk that things might get discarded rather than treated if batch treatment was not an option. With some 35 years of experience, Elizabeth Peacock wisely says we don’t have to advertise that batch treatment is how it is done!
Conservation of Thule Skin Clothing from the Sannirajaq Site, Nunavut
For me, this was maybe the most exciting talk of the conference. Tara does archaeological fieldwork as well as conservation work in the CCI lab. A 2006-2007 excavation of houses from 100-1400AD brought up boots, belts, fur parkas, bird skin inner parkas, gutskin anoraks, pants etc as well as human remains of 8 individuals. After consultation, it was determined to rebury the human remains, and the clothing was excavated separately. There were health problems and strong odors to be dealt with. The precendent of Christchurch, Spitalfelds, England was useful. It seem that lead dust, mold, and parasite eggs are a bigger risk than infectious disease. Anthrax and smallpox can survive, but plague, cholera, typhoid and tuberculosis do not tend to survive in burial. The site was pre-European contact and there were no domesticated animals. The Canadian Science Center for Human and Animal Health was also helpful, and determined that with appropriate personal protective equipment, the staff would be OK. They used a HEPA unit and charcoal filter for odors, mostly from putrescine and cadaverine. These are water soluble compounds that smell even more in high RH conditions. Mary Ballard’s work on this was very helpful. 20g/L water of sodium bicarbonate for proteins and sodium carbonate for cellulosics. The objects she was talking about were mainly a parka with seal fur, caribou fur and birdskins with the feathers still on them. (Cool tidbit, diving birds have stronger skins!) There were also boots of defurred seal skin. Gutskin anorak. They were dealing with hair loss, slippage, dirt, fat, loose/open seams, rips/holes in the skin. Some of the loss or damage was from pre-burial, as evidenced by things like a knot tied in the gutskin near a loss. Tara had really cool slides about gutskin structure. Summer gut is dried in above-freezing temperatures and is not as flexible as winter tanned gut which is dried at below freezing temperatures. They were looking at shrinkage temperature, which as between 45 and 63 for the artifacts, and modern seal and cow are 55C and 60C respectively. There’s a new technique for measuring Ts which is more accurate than the old visual method, so the reference numbers are a little different these days. So on the anorak, for example… They were using 20g/L of sodium bicarbonate, and is thought to preferentially react with amine rather than protein. 30 minutes, agitate, pH of 8 (a little high for skins) and then sodium dodecyl sulphase 0.5w/v as an anionic detergent to remove fats. Brush and cavitron cleaning, then a 17 hour rinse with running water to remove detergent. Repeated detergent and deodorizing, then rinsed for 4 days. They used 20%v/v PEG 400 for 24 hours, and the rinse, tamp, reshape, freeze at -22C. Odor removal was only partly successful. Feathers especially still had some smell, but seams were loosening and feathers were starting to detach so things had to stop. AT the gut didn’t smell at all, and they were able to use a cold mister and finger pressure to manipulate and then clamp into the desired shape.
Conservation of Waterlogged Ivory
Ian Godfrey and C. Wayne Smith
This particular talk was dedicated to the late Sophie Lussier, who did some important work on testing materials to use with ivory. Elephant tusks were found in a 1970’s excavation of a Dutch shipwreck. Tusks form as a cone-in-cone structure. Tendency to delaminate. No relationship between deterioration of ivory and success of treatment options. Some tusks had been “looted” pre-ban and air dried OK, others did not air dry OK. Layer of corrosion products on the outer surfaces were iron rich, and then there was an inorganic matrix better preserved at the core. Calcium would be replaced by iron, and you’d see that lovely blue vivianite. FTIR was the most helpful tool, it is really good for bone and ivory. There was collagen in the rich outer layers, but not in the core. Texture of the ivory was different throughout as well, with some areas as soft as paste and others very hard. Form 1996-99 they tested Rhoplex AC-235 30% for 4 months, Primal MV-23-LO 30% for 4 months, Gelatine 30% at 30-40C for 4 months, Biodur S-10 with S3 hardener and S6 gas cure (plastination) and finally silicone oil (SFD-10 silicone oil with MTMS crosslinker and the dibutyltindiacetate catalyst.) The aqueous treatments were all slow dried over 15 months. The Rhoplex penetrated only 1mm in. Aqueous stuff didn’t really work so well. Really, only the plastination and the silicone oil treatments worked. To do the silicone oil, they bound the tusk so it would not fall into pieces during treatment. For the plastination, they probably ought to have done it at -30C in acetone, but it was done at room temperature in the hopes it would remain more fluid and penetrate better, and so the results maybe not as good as they could have been. They embedded the tusk samples in epoxy and polished it down to look in SEM and see where the material went. There was lots of silicone oil in area with heavy degradation, and then a steady amount in other areas. By making a mixed sample with non-silicone treated ivory, they were able to prove they were not just smearing silicone around during polishing. People were wondering after the talk if the silicone oil treatment would inhibit the oxidation of the pyrite. Looked from this talk like silicone oil might be an appropriate tool for treating this tusk material since there wasn’t really anything else that worked. At the end of his talk, Ian Godfrey brought down the house with killer images of live “flying” penguins from his work in Antarctica. Is it an accident his talk was last? Or was he intentionally chosen as the closer?
Check out additional posts on the business meeting, specific WOAM personalities, the flavor of WOAM, and Lars Andersen’s advice to me on freeze drying at the AIC’s news blog.