Category: Objects Conservation

Emily Kaplan (Presenter), Objects Conservator, Smithsonian National Museum of the American Indian; email: kaplane@si.edu

Ellen Howe, Conservator, Sherman Fairchild Center for Objects Conservation, Metropolitan Museum of Art; email: ellen.howe@metmuseum.org

Ellen Pearlstein, Associate Professor, Conservation of Archaeological and Ethnographic Materials, UCLA; email: epearl@ucla.edu

Judith Levinson, Director of Conservation, Division of Anthropology, American Museum of Natural History; email: levinson@amnh.org

The qero research project is a seventeen-year-long collaboration among object conservators at four museums with qeros in their collections: the American Museum of Natural History (AMNH), the Brooklyn Museum, the Metropolitan Museum of Art (MMA), and the Smithsonian’s National Museum of the American Indian (SI, NMAI). Emily Kaplan (SI, NMAI) presented an update of the research to date on behalf of her co-investigators, Ellen Howe (MMA), Ellen Pearlstein (formerly Brooklyn Museum, now GCI-UCLA), and Judith Levinson (AMNH). The project is an in-depth technical study of materials and techniques of fabrication of a corpus of qeros, polychrome wood drinking vessels fabricated around the time of the Spanish conquest of Peru in 1532; the qeros in these four collections date from the Inca period (13^th-15^th c.), through the Colonial period (16^th-19^th c).  Consequently, the qeros offer material culture insights produced over a span of centuries and reflect the influences of both indigenous cultures and Spanish colonizers.  Principal goals of the project involved: understanding techniques of fabrication, the analytical identification of materials, and the correlation of the technical data with the stylistic data proposed by others (i.e. curators, art historians).

The qero project was an apt presentation for the joint OSG-RATS  session. Kaplan articulately presented the cultural history of the vessels, as well as the technical research undertaken by numerous conservation scientists, principally at the Boston Museum of Fine Arts and at the Metropolitan Museum of Art.  Indeed, both cultural and scientific research were presented in nearly equal measure, which underscored the efforts of the primary researchers to cover both aspects in depth.  Efforts at replication of techniques of manufacture, cultural exchanges with colleagues and artisans in Peru, and the application of the full arsenal of analytical  methods employed (including FTIR, GC-MS, PLM, XRD, and XRF) were discussed.  Kaplan noted that YouTube videos exist showing contemporary Columbian artisans in Pasto working with the sheets of resin.  The presentation was accompanied by quite beautifully photographed images of the vessels themselves, comprised of tropical woods with polychrome resinous inlays, which illustrate geometric (Inca) and figural (Colonial) design registers of increasing complexity.

Funding from the MMA and NMAI allowed Kaplan and Howe to travel to Peru to meet Andean artists and scholars; to collect raw materials; and to visit private and public collections.  Eventually botanical samples of the plant elaeagia were correlated via FTIR and GC-MS to the mopa-mopa resin noted in early literature and the samples from qeros.  Interestingly, the palette was identified as largely unchanged from the pre-Colonial period.  Colorants identified include cinnabar red, orpiment yellow, cochineal red and pink, indigo blue, copper-based greens, carbon black, lead white and titanium white.  A notable, recent reassessment is the meaning of the analytical identification of titanium white (cristobalite anatase in mineral form) on some vessels.  Early in the project, the noted presence of titanium white—a  pigment that found wide usage only in the 20^th century—was  thought to indicate areas of restoration.  Further study focusing on the presence of elaeagia in the media, led the conservators to believe it to be a pre-Colonial pigment.  A known Andean ore does exist.

Current research questions involve study of the ore source(s) of the cristobalite anatase and pigment comparisons to Colonial Andean paintings.  Further, the research and data collection evolved with technological advances and the collaborators are now considering ways to aggregate and share the data on-line.

This research project can be seen as a model for other conservation projects involving multiple institutions.  The sustained curiosity about these objects inspired a prolonged inter-museum collaborative effort , involving international allied professionals.  I’ve followed the progress of the qero project over the years, attending presentations and watching the list of publications in the US and South America grow longer and longer, as new findings emerged.  Near the beginning of the project (which started in 1995), while a graduate conservation student at New York University, I participated for two years as a research assistant on the project.  The concerted efforts to study both historical techniques of fabrication and the scientific results of analytical testing represent for me why the qero project ideally embodies the captivating interdisciplinary aspects of the conservation profession.

Perhaps better known as a medium used in biological studies, agar is gaining traction in the conservation profession as an ingredient for building poultices. The material, a combination of the polysaccharides agarose and agaropectin derived from the cell walls of an alge, is widely available, both in a highly purified form through laboratory supply houses and in a food grade form. It is used as a rigid gel to make poultices for flat surfaces or as more liquid sol-gel for three dimensional surfaces.

Cindy Lee Scott’s study of this material and possibilities for its use in removing shellac from ceramic surfaces was inspired by work using agar gels to clean outdoor plaster busts presented in 2010 by Paolo Cremnesi and published by Anzani et al. In their work, deionized water was the primary ingredient in their poultices, but Cindy Lee wondered if solvents and other cleaning agents could be added to these mixtures to extend their versatility and how these additions might change the stability and working properties of the gel.

After reviewing various properties of the material, particularly the manner in which the porosity of an agar poultice could be modified by altering its concentration, and then the  manner in which the gel is typically prepared, used and removed from a substrate (it peels off the substrate cleanly), Cindy Lee presented her own work, conducted in two phases.

The first phase of her work, a component of her thesis as part of her studies at the UCLA/Getty program, involved exploring agar as a gelling material for various cleaning agents on terracotta test tiles coated with a kaolinite-type slip with the goal of finding new ways to removing shellac from previous restored ceramics. She tested agar sol-gels mixed with ethanol, acetone and 5M sodium hydroxide, alone and in combination. She looked at efficacy of cleaning and clearance using visual analysis using a binocular microscope, UV-fluorescence microscopy, and FTIR spectroscopy.

She found that these agar gels performed beyond expectations particularly in comparison with other options tested for that study. She found that agar sol-gels had excellent working properties when they were mixed with ethanol and sodium hydroxide and had good clearance from the surface. Clearance improved for gels with a lower concentration of agar when Japanese paper was used as an intermediary layer.

The second phase of Cindy Lee’s work, undertaken during her internship at the Museums of New Mexico, extended the number of cleaning agents added to agar gels. Additives included solvents, surfactants, chelating agents, oxidizers, and acids. She noted working properties of each mixture, color changes to the gel that might lead to staining, and stability of the resulting gel. In this phase, access to analytical equipment was limited, so her analysis was generally limited to visual observation. Additionally, these mixtures were applied to plaster tiles coated with various materials including alizarin dye, shellac, various paints, PVA emulsion, and soil and artificially aged to test cleaning and clearance.

To summarize very quickly, as far as adding solvents go, best results for workability were achieved with ethanol, then Stoddard Solvent followed by acetone and xylenes. She noted that solvents added in too high a concentration could cause the gel to dissociate. Good working properties were also noted for gels made with the chelating agents, oxidizers, acids and bases tested. The surfactants tested caused complete dissociation of the gel. As far as cleaning efficacy, it appears that gels tested had a more difficult time removing dye and smaller particulates, but with regard to smaller particulates, concentration of agar within the gel appears to have a great influence. She found that efficacy could be improved by altering concentrations of agar and solvent, the temperature of the poultice on application, the length of application and number of applications of the poultice.

Cindy Lee concluded her presentation with  pros and cons of using agar-based solvent gels for objects conservation. Since she was kind enough to provide me with her paper and slide deck to help me write this post, I will share them here (if you click on the image it expands):

In short, I found her presentation to be an excellent introduction to this material and I can’t wait to experiment with it myself. It was also excellent to see the kind of simple testing we all do regularly in our own labs presented in a RATS/OSG session, and I look forward to seeing this work published. I don’t presently use Agar, but her presentation has encouraged me to do some experiments to see if this material would be appropriate to use in my own practice.

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…

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).

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!