Specialty Sessions – Page 39 – AIC Blog Archives: Conservators Converse

AIC’s 40th Annual Meeting, Objects and Research and Technical Studies Joint Session, May 9, “A Comparative Study of Protective Coatings for Marble Sculpture in the Museum Setting,” by Laura Kubick

One of the reasons I enjoy joint sessions is the more focused theme and connection between the talks. Laura provided a nice overview of the research that she carried at out at SAAM on marble coatings. Three white marble sculptures in the collection- by Rinehart, Cooper, and Houdon- attract a lot of attention and love from the public. Some love comes in the form of red lipstick. Laura took this as an opportunity to explore traditional and newer materials for coating marble and determine which have the best protective properties.

Her testing methods appeared thought out and well carried out. She tested Cosmoloid 80H wax and Ketone N resin, Renaissance microcrystalline wax, Methocel A4C Methyl Cellulose, and Avalure AC 315 Acrylic Copolymer 5% and 7% in ethanol. She tested polished and unpolished marble. All the coatings were applied by brush. They were tested for their appropriate aesthetic properties, effectiveness as a barrier, safe application and removal, reversibility and aging. Quite a feat if I say so. Needless to say there is more testing that can be done. However, her initial findings are quite interesting. To measure changes in color and gloss Laura used a Spectro Eye spectrophotometer and gloss meter. The marble samples were stained with lipstick, red wine, and a sharpie. Laura provided a nice graphic showing her samples and the order of testing, aging, cleaning, etc.

Overall, from the testing Laura concluded that none of the coatings were perfect. There is a give and take with all. However, most importantly Renaissance wax was NOT a good barrier- I found it shocking that the red wine etched the marble through all of the coatings except Avalure. The wax resin and avalure did the best in the aging test. Methyl cellulose had the best reversibility, while microcrystalline wax was the worst. It was also interesting to hear that the colorimeter readings were consistent with what she observed by eye. Although nothing can replace scientific readings it is nice to know that our trained eyes are good for something. She also felt that more research should be done on methyl cellulose and Avalure since they tested tested so well. Her tests were only done on small samples, but the practicality of applying it to a large sculpture might change things. Avalure is somewhat difficult to work with, but perhaps a spray application would be better. By the way, Avalure is available through the manufacturer and apparently they are generous with their free samples.

I don’t know if this would be possible, but a follow up to this study might be interesting to look at the penetration of these coatings into the marble. Perhaps looking at a cross-section with FTIR-ATR…

AIC’s 40th Annual Meeting, Objects and Research and Technical Studies Joint Session, May 9, “In Their True Colors: Developing New Methods for Recoloring Faded Taxidermy” by Beth Nunan and Judy Levinson

After 70 years on permanent display, the taxidermy at AMNH got a much needed renovation. It was beautiful to see the artistry behind the construction and design of the original dioramas. This talk focused on the fading and discoloration of the fur and hair of the animals. The care that was taken in reproducing details from actual locations in the field was amazing- such an elaborate process. The background paintings are true works of art. It is wonderful to see that they are being maintained. There are a limited amount of actual materials used, such as evergreen branches and grasses. The rest was replicated for the dioramas.

So in 2003 there was a survey done of the dioramas and this resulted in a reduction of heat and light in the display areas by moving from theatrical lights to fluorescent and tungsten and screening of UV. In 2010, through a citywide effort to reduce energy use by 50% they moved to LEDs, metal halide, and T8 fluorescents- still screening out UV. However, they haven’t been able to reduce the light levels from 50 and 65 fc to an acceptable conservation level of 5 fc because of the desire to replicate the natural environment. The lights stay on even at night! Beth and Judy can give you the name of who to contact to help them in their campaign to shut off those lights!

AMNH hired an artist to recolor the taxidermy. They chose the colorant based on the solvents needed (these were restricted because the painting had to be done in open galleries with limited fume extraction), reversibility to not prevent future treatment, light fastness, Tg, application method and appearance. Water based acrylics were eliminated because of the low Tg and difficulty for re-treatment. They were leaning towards Orasol dyes and XSL pigments due to these criteria, but he taxidermist had to be won over from their usual use of acrylics. Luckily they were successful!

Finally, Beth carried out light-fading tests to determine which would be the best colors to use. Samples were colored and sent to Paul Whitmore for microfading tests. The microfadeometer is limited by a threshold and this is not equivalent to the real light exposure they will get in the dioramas. So out of view of the visitors they have put samples for future comparison with areas that are covered to block out the light.

The authors got a lot of thoughtful questions about the amount of degradation of the hair (a lot), if a special brush was used for grooming (yes), if the dyes were applied with ethanol (yes), if they could turn off the lights at night (they wish!, please contact the museum to push for this), and what was used for the yellowed fur (XSL pigments had the best covering properties).

40th Annual Meeting, Objects and Research and Technical Studies Joint Session, May 9, “The Qero Project: Conservation and Science Collaboration Over Time” by Emily Kaplan

After hearing about this project in the past couple of years, I was looking forward to learning more about the evolution of this 16 year collaboration and some of the observations and conclusions that have come out of it. I applaud the original participants (including conservators: Emily Kaplan, Ellen Pearlstein, Ellen Howe and Judith Levinson) in their ability to continue their involvement over the past decade and with various geographic and institutional changes. Analytical participants include the MFA Boston, the Met, Yale, MCI, and University of Barcelona. Emily spoke about the benefits of working on this project over an extended period of time- for example, they are taking fewer and smaller samples now, there is increased collaboration, and improvements in technology have moved them from paper to an electronic shared database.

This project came about when Emily was a post-graduate fellow at the NMAI (when it was in NY), the Brooklyn Museum of Art was preparing for an exhibit, and the Met received a large gift. Several exhibits and publications came out in the early years of the collaboration. Some of the goals were to study the imagery depicted and the polychrome techniques as this was of interest to the conservators, but also to better understand the people, production and use. Qeros are drinking vessels used in the Andean region for consuming fermented beverages. They are sometimes made in pairs, but few still remain together, and have been made from a variety of materials including wood and metal. Qero actually means both wood and cup. They have been described and illustrated in colonial chronicles, sermons and legal documents. Qeros are still used today as this tradition persists.

So far they have identified organic and inorganic pigments: orpiment, cinnabar, cochineal, indigo, copper greens and carbon black. These all have potential local sources. There has been a renewed interest in Qeros and an authoritative book came out in 2002 by Thomas Cummins. The qeros have been dated stylistically and categorized into four periods (sorry I didn’t write down all the dates and I wish I had a photo of this slide): the Inca period (1425-1532) having incised decoration, the early Colonial period (1600-1650) having small areas of polychrome and incised decoration, the Mid Colonial, and the late Colonial.

The most recent research has focused on the white pigments. Three types were identified: cristobalite, anatase and white lead. They are also doing lead isotope analysis and finding two sources for the lead. Apparently lead ore was common in the Andes, but it wasn’t used as a painting material until after the arrival of the Spanish.

I loved seeing the images of a workshop on working with mopa mopa- a resin that was noted as a binder in early literature. Through working with the mopa mopa Emily could see how it was applied to the surface after being pulled into strips, laid on the surface and then heated.

It was nice to see the benefits of an extended project like this one. I’m sure Emily would appreciate knowing about Qeros in other collections if you have any!

AIC’s 40th Annual Meeting – Objects Luncheon: “So Far Away From Me? Conservation and Archaeology” by Suzanne Davis and Claudia Chemello

In the second talk during the OSG luncheon, Suzanne Davis and Claudia Chemello explored the question “are archaeologists and conservators so far away from each other?”, inspired by the sentiment of the Dire Straits song “So Far Away”. Their talk was illustrated with historic photographs of archaeologists working in Tunisia, Egypt and Turkey in the 1920s, from the collection at the Kelsey Museum of Archaeology at the University of Michigan.

As a follow-up to last year’s annual meeting presentation, which summarized the responses of a survey of archaeological conservators, this year Suzanne and Claudia presented the results of a 2011 survey of archaeological dig directors working primarily in the US. The purpose of the survey was to examine how archaeologists are engaging with conservators, to gain an understanding of conservation needs from an archaeologist’s perspective, and to identify areas for outreach and education.

They made the survey using the online survey tool Qualtrics and after wide distribution, received a whopping 346 responses.

They plan to publish the complete results of the survey, but in their presentation, they summarized a lot of the data, such as:

Half of the respondents are employed in an academic environment and half are employed in non-academic organizations.
41% have employed conservators in their projects. The 59% who have not said that it was due to lack of funding.
Most respondents spent between 1-30% of their budget on conservation, and the most frequent amount spent was $10,000/season.
55% said that conservation is expensive or prohibitively expensive.
Of those who have employed conservators, 38% have not received conservation reports, which corresponds with the 25% of archaeological conservators surveyed who do not write conservation reports for the sites they work on.
74% have never heard of AIC.
13% have used AIC resources.

Suzanne Davis broke up their presentation of this data by leading the audience in singing a few verses of Dire Straits- So Far Away.

In general, the archaeologists’ responses showed that there is a confusion between the terms “curator” and “conservator”, and they expressed that they feel that many conservators don’t have sufficient field training, nor do they understand archaeological research goals but that they feel that conservation is a necessary expense for archaeological projects.

Based on this survey, what do Suzanne and Claudia recommend? In essence, they said, to paraphrase Mark Knopfler, lead singer of Dire Straits, “we need to stop making love over the phone.” They said that while conservators and archaeologists are not so far away from each other, conservators need to work on increased and sustained outreach to archaeologists and to develop more resources for the AIC website or on the AIC WIKI specific to archaeology, particularly regarding funding sources and site preservation. They also indicated a need to improve education to further integrate archaeological and conservation research.

We think that the results of this survey are so interesting and help to provide hard data on topics that are often speculated on by archaeological conservators. We hope that Suzanne and Claudia are able to publish the entire results of the survey and we look forward to hearing more about efforts to improve the relationship between conservation and archaeology, and to contributing to this effort as much as possible.

-Vanessa Muros and Molly Gleeson

AIC’s 40th Annual Meeting, Book and Paper Session, May 11: “New Book and Paper Conservation Products and Processes from the Heritage Science for Conservation Laboratory” by John Baty

According to John Baty, he’s got a dream job: working side by side with conservators in a book and paper lab that bridges the gap between scientific analysis and bench work. You might call it practical science, or treatment-driven analysis. In either case, Baty argues that the Heritage Science for Conservation Laboratory–part of the Department of Conservation and Preservation in the Sheridan Libraries at Johns Hopkins University–is a model the rest of us should follow. Plus, the Andrew W. Mellon Foundation-funded lab has developed some cool toys we can use in our own paper-based research.

For Baty, the collaboration between chemists and conservators is key. (How’s that for alliteration?) This meeting of the minds has led the HSC Lab from fundamental research into the degradation mechanisms for cellulose to the production of tools that can help other conservators and conservation scientists in their work–particularly if they are engaged in studies that make use of accelerated aging. During his talk, Baty introduced three of these tools and the data that support their usefulness.

The first technology he discussed was the range of common-ion effect buffers that can be used to maintain a given pH in paper. These buffers, which take advantage of the equilibrium between a weak acid and its conjugate base, establish a narrow pH range that resists change, even after accelerated aging. Research at the HSC suggests that phosphate buffers added to paper remain effective after 42 days of accelerated aging, even at higher temperatures. In aging studies, these buffers can be used to minimize the number of variables acting on the test papers as they age. In theory, such buffers could also be used to maintain a pH range that would slow the deterioration of ir0n-gall ink or prevent color shifts in pH-sensitive dyes and pigments.

The HSC has also developed a new vessel for accelerated aging, after noticing hairline cracks and other failures in the vessels currently in use. The new closed tube, which features a glass-on-glass seal, was developed in collaboration with conservator Bill Minter. It can withstand high pressures without losing moisture, and because it has no gaskets, its contents cannot be contaminated by residual polymer chemistry or offgassing from faulty seals.

Finally, Baty introduced a calibration kit that will allow scientists and conservators to calibrate their X-Ray Fluorescence (XRF) or Near Infrared (NIR) spectrometers for nondestructive paper analysis. The kit contains paper targets uniformly coated with specific salt concentrations.

AIC’s 40th Annual Meeting, Book and Paper Session, May 11: “Preservation of Cultural Heritage: The Restoration of the Globe in Relief” by Maria Gabriela Mayoni

In the last BPG session of this year’s AIC meeting, “global conservation” took on a whole new meaning. Maria Gabriela Mayoni, a conservator of cultural heritage from the Colegio Nacional de Buenos Aires, Argentina, delivered a lavishly illustrated lecture concerning the conservation of a papier-mache globe and its support. This globe, manufactured in Germany in 1850 and bearing site labels in French, belongs to the Department of Geography of the Colegio Nacional and illustrates the European influence on Argentina during the nineteenth century–a period of nation-building and economic development. At some point in the past, the rare globe was seriously damaged in an accident: a large section was crushed, a portion of the papier-mache sphere was lost, and the support rings were deformed. The varnish coating the globe had also darkened and discolored, making the labels and land masses hard to read. The area representing Argentina had been overpainted, perhaps to keep up with changing geopolitical boundaries.

Mayoni described the complex structure of the globe, which included a papier-mache sphere with outer layers of cast composite, paper labels, paint, and varnish. This globe was mounted on a wooden axis, fitted with metallic rings, and placed on a stand made of iron and wood. All of these elements were addressed during the comprehensive conservation treatment of the globe.

Prior to beginning treatment, Mayoni and her colleagues analyzed the materials present on the globe with FTIR, and the results were consistent with an oil and natural resin varnish. This was cleaned with a mixture of water and ethanol, which was applied carefully to avoid disturbing the water-sensitive inks on the printed labels. After the varnish had been reduced, the conservators split the globe into its two original halves. Inside, they discovered labels containing information about the globe’s manufacture, including a date decades earlier than they had anticipated. The crushed portions of the globe were humidified and reshaped, and the losses were filled with a vinyl acetate adhesive and long-fibered paper. After the sphere had been mended from the inside, the two halves were reassembled, and the join was reinforced with cotton fibers. A combination of animal glue and calcium carbonate was used to fill the losses in the topographical relief. The deformed metal rings were reshaped, polished, and given a protective coating. The wooden elements of the stand were also reshaped as necessary to return the globe to usefulness.

Mayoni noted that the varnish selected during treatment will have to be replaced in a second conservation campaign. The reassembled sphere was varnished with a soft synthetic resin soluble in white spirits. Harder, solvent-soluble resins were rejected because the solvents used to reverse them would have affected the inks on the labels. However, the soft resin has become yellow and grimy since it was applied. After further testing, it will be replaced with something more durable and colorfast.

The globe is once more in use in the Geography Department of the Colegio Nacional de Buenos Aires, where the students and faculty learn the importance of preserving their cultural heritage as well as their place on the map.

AIC’s 40th Annual Meeting, Book and Paper Session, May 11: “Case Study: Examination and Analysis of a Mesoamerican Deerskin Map” by Ted Stanley

Ted Stanley wrapped up the Book and Paper Group sessions on Friday, May 11, with his presentation about the authentication and analysis of a 16th-century Mesoamerican map belonging to Princeton University Library. The map was believed to have a c. 1550 creation date, and depicts a portion of the central valley of Mexico at the time of the European conquest. Stanley attempted to determine the authenticity of the deerskin map through noninvasive analysis techniques, including light microscopy, UV-induced visible fluorescence, UV-VIS spectroscopy, and FTIR.

The map, which features black, blue, green, red, and yellow colorants on a leather support, depicts the upheaval in Mexico at the time of European conquest. Hernan Cortes famously invaded Mexico in 1519. The priests who followed in his train destroyed Maya and Aztec maps and codices, and Spanish conquistadors killed many indigenous people, especially those who resisted conversion to Christianity. In one of the map’s illustrations, priests preach to native noblemen, perhaps with limited success: one priest is shaking an Aztec listener so violently that blood flies from his nose. The map also illustrates roads, waterways, villages, agave plantations, and irrigation systems, accompanied by Aztec glyphs or pictograms and their Spanish translations, or glosses. It captures the meeting of the Old and New Worlds, with depictions of Aztec warriors, Spanish priests, Aztec shrine altars, and colonial Spanish villages. But is it authentic?

According to Stanley, the hide support was roughly scraped as part of the tanning process; he is still investigating how the Aztecs may have treated the skin to preserve it. Large, circular voids in the leather appear to be the natural result of abscesses in the animal’s skin rather than later damage. The map was previously folded and has prominent creases as a result. Its pigments are stable, with minor abrasion, and the map displays some liquid staining and minor losses along the edges.

Since no follicle pattern could be determined using light microscopy, Stanley compared the collagen fibers present in the map’s support with those of a known deerskin, and found they had comparable length and width. He also examined the map’s colorants and found evidence for both yellow and orange dyes, which were absorbed into the collagen fibers, and for blue, green, and black pigments, which were deposited on the leather surface.

Stanley then used UV fluorescence for general pigment identification, comparing the fluorescence of the map’s colorants to the fluorescence of Kremer pigment samples. Based on his observations, he tentatively identified the red colorant as cochineal, the yellow-orange as gamboge, and the blue as Maya blue, a combination of indigo and palygorskite clay. While cochineal and Maya blue are both associated with traditional Aztec culture, the gamboge was a surprise, since it is normally associated with Southeast Asia. In addition, the fluorescence of the green pigment did not match that of any Kremer samples. UV-VIS spectroscopy of the map’s colorants reinforced Stanley’s original pigment identifications, but the green remained a mystery.

Finally, Stanley turned to Fourier-Transform Infrared Spectroscopy using Attenuated Total Reflectance (FTIR-ATR) for more definitive pigment identification. Once the bands for the hide support had been subtracted, the spectrum for the red dye displayed the characteristic absorption band for carminic acid, confirming the presence of cochineal. The yellow-orange dye produced an absorption band for gambogic acid. Stanley theorizes that the gamboge present in the map is actually American gamboge, a resin that is chemically identical to Asian gamboge but originates in a Mexican plant. Both the blue and green pigments produced spectra containing absorption bands for indigo and palygorskite clays, suggesting that they are Maya blue and Maya green: the same pigment/dye complex at lower and higher pH levels, respectively. The black pigment produced absorption bands for calcium and phosphate, indicating the use of bone black.

Because all of this evidence points to the use of pigments and dyes known to have been used during the early colonial period, Stanley has determined that the map is likely to be contemporary with the European conquest of Mexico. However, the colorants, the skin, and the tanning process all provide tantalizing opportunities for further research. Could the green colorant be Maya blue in combination with a yellow dye? Is the leather in fact deerskin? How was it tanned? Finding the answers to these questions could shed more light on the map’s authenticity, and illuminate a period of dramatic historical change with even more accuracy.

AIC’s 40th Annual Meeting, Objects Luncheon: “Holy Mammoth, Batman! Conservation Education and Outreach for the Preservation of a Columbian Mammoth” by Vanessa Muros and Allison Lewis

This year’s OSG luncheon featured 2 archaeological-focused talks, each sprinkled with pop-culture references.

Vanessa Muros spoke first-a presentation titled “Holy Mammoth Batman! Conservation Education and Outreach for the Preservation of a Columbian Mammoth,” which was co-authored by Allison Lewis.

This presentation addressed the issues and challenges of training archaeologists in conservation techniques, and covered some of the outcomes-both good and bad-of such a collaboration. In the fall of 2010, Vanessa and Allison were contacted by archaeologists from Foothill College in Los Altos Hills, CA to advise them on the excavation of the fragile remains of a Columbian Mammoth. This was an unanticipated find and the archaeologists had no money to hire conservators and Allison and Vanessa had very limited time (or perhaps desire since they would be working for free) to spend in the field.

The solution that Vanessa and Allison devised was to act as consultants and to go out into the field to assess the condition of the remains and the possible treatment options, to devise protocols for safely lifting the mammoth remains and to train students working on the project to carry out this work themselves. After speaking to the archaeologists about possible analysis of the remains and ensuring that all sampling had been carried out, they devised protocols that involved consolidation of the bone and ivory remains in situ with Acrysol WS24, facing with cyclododecane, and block-lifting.

Vanessa took several block-lifted items back to the UCLA/Getty Conservation Program training labs at the Getty Villa, and, along with the graduate students, devised protocols for further stabilization of the excavated pieces using Acryloid B-72 for the dry bone and Acrysol WS24 for the bone that was still damp. Packing and storage solutions were also devised in consultation with Foothill College so that they could be replicated by archaeology students for the rest of the excavated material back at Foothill.

In the end, Vanessa and Allison deemed the collaboration a success-they felt that the archaeology students learned about conservation techniques, materials and proper storage, and the mammoth remains were safely lifted and stored. They also felt that they had promoted conservation and demonstrated the skills and knowledge required to be a conservator. Despite these great outcomes, they also saw several potential issues, including the fact that the project director, in the project’s Flickr photo album, labeled photos of archaeology students as “conservators.” Did the project director understand that his students aren’t conservators? Had they undermined our profession by demonstrating that non-conservators can do this work, and by teaching non-conservators irreversible and challenging treatments? Had they devalued conservation by volunteering to do all of this?

For being a potentially controversial topic, there were surprisingly no questions or objections about any of this by anyone in the audience. Personally, I think that this project is good for conservation- instead of trying to do the work themselves, the archaeologists contacted Vanessa and Allison, which I believe is an acknowledgement of the expertise and skills of conservators. And I think that while Vanessa and Allison trained students to carry out conservation methods, they did it in a way so that those students do NOT feel like they are conservators (even if the dig director may not fully understand). I also believe that these archaeology students will probably be even more likely to contact a conservator in the future, since this appeared to be a very positive collaboration. What I’d like to see, however, is archaeologists involving conservators like Allison and Vanessa from the beginning of projects. I know that there are always unexpected finds, but if conservators are involved from the beginning, there will hopefully be funding and time to carry out such work in the case that conservation is needed. Projects like this demonstrate the important relationship-building necessary for this collaborative work to take place.

AIC’s 40th Annual Meeting, Architecture Session: “Biofilms and Weather Resistance of the Rhyolitic Tuff: Preservation of the Cavates and Petroglyphs at Bandelier National Monument”, May 11, 2012

Doug Porter, of the University of Vermont, teamed with Angelyn Bass, of the University of New Mexico, to present their recent work at Bandelier National Monument in New Mexico. Their project began as a structural monitoring program, in collaboration with MIT, and Angelyn first walked the audience through the computer modeling investigation of a particular section of rock. The modeling was meant to investigate structural stability, collapse scenarios and potential failure points. Doug then discussed the geological formations at the park and the presence of a clay & calcite deposition in combination with biofilm colonization which the team thought could be providing structural stability and weathering resistance to the tuff rock. Their site investigation included absorption tests for those areas covered with biogrowth in comparison to recently exposed surfaces. They also looked at permeability and erosion resistance. The presentation acknowledges that biogrowth is identified as a deterioration process in most cases, but may also be contributing to the preservation of the substrate.

AIC’s 40th Annual Meeting, Architecture Session: “Gelatin as an Adhesive for the Reattachment of Decorative Earthen Surface Finishes”, May 11, 2012

Emily Aloiz presented a recent treatment investigation to address blistering and delamination of earthen finishes at Mesa Verde National Park in Colorado. Her study continues the work begun in 1994 at this site by Professor Frank Matero and the graduate students of the University of Pennsylvania program in Historic Preservation. (http://repository.upenn.edu/hp_theses/178/ ) The need to identify an adhesive which would re-adhere delaminating earthen finishes within the alcove sites of the park was guided by a desire to be respectful of the site’s Native American culture by choosing a natural product. Other parameters which were identified included: practical, inexpensive, non-toxic; durability in an outdoor environment and compatible with sandstone and earthen materials; re-establishes adhesion; retreatable; and versatile. Laboratory tests were conducted on a group of proxy samples using a food-grade gelatin as well as the gelatin with the addition of glycerine. Emily carefully laid out the methodology followed during these tests to analyze bond strength, changes due to freeze/thaw and wet/dry cycles and humidity fluctuations. Because the gelatin is organic, biodeterioration was also a concern and was addressed by placing petri dishes of the gelatin solutions at the site as a monitoring system. Once laboratory tests confirmed the feasibility of the use of these gelatin solutions, treatment was carried out in situ by syringe injection between the earthen finish and the substrate. Where there was carbon soot present on the surface, it was first treated by applying cyclododecane as a spray.