Category: Research and Technical Studies

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!

Presenter: Paul Benson

Sulfur is well known as an agent of deterioration associated with atmospheric pollution, but sulfur was, and still is, intentionally introduced into buildings as part of the construction process, and is a part of some objects in museum collections. This presentation by Paul Benson was tremendously informative about how sulfur may be hiding in plain sight and damaging collections.  The talk provided examples of the use of sulfur past and present, and provided an example of effective control of sulfur used in the construction of an exhibition space.

Molten sulfur is an excellent electrical insulator. It has very good adhesive, handling, and casting properties that make it a good fill material. It goes through a flexible stage when cooling and it expands slightly (3%) on setting. In the US plaster ceilings were repaired with molten sulfur until the 1920s and buildings built before 1940 may have sulfur behind the surface of the walls as an insulator or fill material.   Conservators carrying out CAP surveys should be mindful of these possibilities.

There are unsuspected modern uses of sulfur as well. Used as an inexpensive filler in Chinese-manufactured dry wall imported to the US between 2001 and 2009, it caused extensive damage and reconstruction. Sulfur with additives is used instead of Portland cement in Canada because it has considerable shorter set time.

The Nelson-Atkins Museum discovered that the cause of severe mottling of bronze sculptures was sulfur applied behind the  numerous travertine sides of display cases integrated into the structure of the walls.  This situation was successful remediated by removing each piece of travertine, and applying  Marvelseal® with Beva®.

Sulfur has been used as a fill material in bombs. Police forensics use sulfur to take very accurate casts of footprints in snow.  These objects may be stored for long periods of time and contaminating other evidence.

Molten sulfur has been used since antiquity as an adhesive.  Pliny may have described its use as an adhesive for glass (depending on the translation). Sulfur was used as an adhesive in Rome, Greece, and Byzantium. All stones in the Thetford treasure at the British Museum were set with sulfur.  Sulfur was used to secure iron rods holding together elements of stone sculpture.

Sulfur can be found as an inlay material in furniture marquetry particularly in the sixty years from 1760 forward.  Sulfur will take on the appearance of mother of pearl with repeated heat treatments and can be found as “pearl” inlay on guns and  guitars.

Objects may be made of sulfur. “Spences Metal” is an iron-sulfur alloy used in the years around 1880. It can take a high polish and imitate a variety of metals. At the time hoped to be in inexpensive replace for bronze. “Ebonite” was made of rubber with 30-40% sulfur and was used to manufacture buttons and casters for furniture among other utilitarian objects that may be in museums of attached to objects in a collection.

Sulfur has been found in an historic clock cast around the weight to hold it in place. The “lead”  of German pencils made before 1770 is a combination of graphite mixed with sulfur. Coins may have been cast in sulfur lined plaster casts.  And among the seemingly innocent items that might be in a conservation lab sulfur is present in Plasticine® and pencil erasers.

This presentation provided a useful warning about possible contamination from sulfur present in unpredictable places and provided a wide range of examples to guide in hunting for an unseen source of corrosion.

The original topic of this talk shifted from the analysis of sculpture created by the “Finish Fetish” artists using ATR (attenuated total reflection) to a discussion of the materials and methods of fabrication employed by three of these artists: Craig Kauffman, John McCracken, and Larry Bell. Though not accepted by the artists themselves, “Finish Fetish” was a name bestowed upon a group working in the L.A. area in the 1960s referring to the cool, yet pristinely finished surfaces that were characteristic of their art. Rachel noted that care must be given to preserving the signature surfaces, thus any analytical investigations required the use of non-invasive techniques only. The materials examination was augmented by interviews with artists when possible, as well as archival documents.

Craig Kauffman, one of the first artists to use plastics in the L.A. art community, converted industrial fabrication methods into his practice. Heavily influenced by Marcel Duchamp, his early work involved painting, typically with clean lines, on the back of acrylic sheets composed of poly(methyl methacrylate), confirmed by ATR analysis. By 1964, he had begun shaping the acrylic sheets by vacuum forming, collaborating with a manufacturer. The acrylic was heated in an oven until it softened, then shaped on a mold to create shallow reliefs. Kauffman’s sketches reveal plans for fiberglass molds with wooden supports, which were especially necessary for his later experimentations with depth and complexity. The transparent shells were subsequently painted, using thick rubber masks to create crisp lines. Later, he created a feathered look by spraying the paint over a cardboard mask, which served to soften the lines. He eventually shifted from solvent-borne acrylic-based paint, an ethyl methacrylate/methyl acrylate co-polymer, to nitrocellulose paints, since the solvent-based paints caused the substrate to craze and crack.

Rachel went on to discuss the technique and materials of John McCracken, who is reported to have said he wanted his sculptures to look as if they were “made of color.” They generally consisted of wooden planks coated in a layer of fiberglass, followed by a primer and various layers of paint, later switching to polyester resin application instead of paint. To make grooves in the surface, he would mask the lines with painter’s tape, then coat exposed surface in the polyester resin mixed with pigment. He consistently jotted down ideas and sketches before producing technical drawings, and even kept a notebook recording the varying temperatures and amounts of catalyst used for the resin as he experimented, making note of how it affected the working time, as well as the properties of the resulting work. Regardless of the conditions, the application of resin to the surface of the planks required an experienced and steady hand in order to avoid the evolution of bubbles in the resin layer (as any novice conservator embedding their first few paint samples for cross-sections knows!). The final step involved sanding of the surface to a smooth sheen.

The last artist Rachel broached was Larry Bell, who worked not with plastic, but with glass. Originally a painter, he would add mirrors to his compositions to introduce volume, eventually deciding that he wanted to work exclusively with volume. He worked often with plywood, mirror parts, and paint, though he increasingly favored glass, such that his paint became instead the effect of light as it was manipulated by the glass. In 1962, he began experimenting with the vacuum deposition of thin films to the glass, soon after which he bought a secondhand machine to execute the process himself in 1966. This purchase allowed him the freedom to create larger panels, which also corresponded with a shift into more environmental art. The vacuum chamber heated the metal under vacuum to a temperature at which the metal vaporized and was deposited on the surface of the glass as a micron-thin film. The three metals most commonly used by Bell were aluminum, silicon monoxide, and nickel-chromium alloys, otherwise known as ‘Inconel.’ The thin film of metal influences the way light is reflected, refracted, and transmitted through the glass. Bell also experimented with changing the temperature and combining metals, all while monitoring the chamber through a window to assess the changes. Rachel noted that Bell, the only artist alive of the three discussed, is actively involved in the conservation of his work, providing conservators with replacement panels when they break.

The above represents but a small portion of the project embarked upon by the GCI (Getty Conservation Institute), a study of the materials and working methods of these and other artists active in the LA area during the postwar period who borrowed from modern industry. The study is a part of both the Pacific Standard Time initiative that included a recent set of exhibitions across Southern California sponsored in part by the The Getty. It also represents the GCI Modern and Contemporary Art research initiative. Future plans include a publication to disseminate the work, a short video, and an exploration of practical applications for the information gained, such as ways to mend cracked and chipped polyester and acrylic resin. Ultimately, the research of Rachel and her colleagues, Emma Richardson and Tom Learner, will hopefully help facilitate treatment decision-making for conservators working with modern and contemporary artwork.

I’m not an educator, but while listening to this talk I was thinking “Sign Me Up!”. Dr. Hill spoke about the intensive workshop provided for educators who want to improve their science classes or start new ones. She’s a professor at Millersville University and wants conservators to know that chemistry professors are safe to connect with! The overarching program of cCWCS (Chemistry Collaborations, Workshops, and Communities of Scholars) covers many topics, but she focused on those that combine chemistry and art. You can check out their website (there was a typo in the original talk title) and find lots of materials if you aren’t able to attend the workshop or you’re just interested in finding out more about what they do. If you are thinking about starting a class or want to improve a class that you already give this 5-day intensive workshop might be for you. And it’s all expenses paid, thanks to the NSF. Their target audience is undergraduate faculty and staff and includes mainly chemists, practicing artists and art faculty. They are interested in having more representation from the conservation community. It sounds like a fun way to get the word out about what conservation is and what conservators do as there is a high degree of confusion about the difference between curators and conservators amongst this group. Also, you could potentially make some helpful contacts in the chemistry world.

The participants come from all over the country and generally fall into four categories:

1. those how are looking for a fancy vacation (really a minority)
2. older faculty who now have more flexibility in their schedule and are looking to pursue interests outside of their previous research and bring excitement to their students
3. mid-career faculty who are looking for a unique area of research or trying to find their teaching niche
4. and community college faculty who are looking for support and to bring interesting applications to students to engage them and get them more enthusiastic about science.

Vicki Cassman is an example of one of their alums who attended a session in 2010 and took what she learned back to UD for an honors seminar.

In 2009 they started an advanced workshop, the third of which will be held this summer. During this workshop they discuss ethics and understanding the questions you are trying to answer before starting analysis. Participants can bring an object that they have questions about and then they share the results with one another.

In the future they are looking for ways to broaden the community and making resources available to educators. Thanks to Nancy Odegaard and Dr. Hill for bringing this to our attention.