Surveying Historic Taxidermy Part 2: Fun Finds

At its outset, execution of our inventory and condition survey of taxidermy mounts in storage in the American Museum of Natural History’s Department of Mammalogy (see previous post) required clarification of what exactly can and cannot be considered “taxidermy.”

What exactly is taxidermy?

The word taxidermy is derived from the Greek words “taxis” meaning arrangement, and “derma” meaning skin. Strictly speaking, a specimen must have preserved skin that is arranged in a lifelike form to be considered taxidermy. Taxidermists achieve this using different materials and methods, but in our survey we considered a specimen to be “taxidermy” if it had an articulated pose and glass eyes (indicating that it was meant to be exhibited). This criteria discounted study skins (preserved specimens with stuffing, but without an articulated pose or eyes), skin rugs (preserved hides with glass eyes and reconstructed head, but without an articulated pose), and mummies (specimens that may appear articulated, but lack internal armature or glass eyes).

hutia mummy

Hutia “mummy” that appears to be in a lifelike pose, but further inspection reveals that there is no internal armature and no glass eyes. This specimen therefore was not considered taxidermy.  AMNH/F. Ritchie

rat drawer2_1

Rodent drawer of study skins that have glass eyes, but not articulated poses, and therefore are not considered taxidermy.  AMNH/F. Ritchie

The bat collection proved to be the trickiest to classify because a majority of specimens were mounted onto external glass panels. They were not fully articulated internally to form an accurate lifelike pose. It is difficult to pose the thin skin of bat wings, especially of smaller specimens, because, having qualities similar to parchment, it deforms and tears easily.

807_1_overall

Bat specimen mounted to an external thick glass plate. Note the glass eyes and articulated mouth.  AMNH/F. Ritchie

The glass plates provided a way to support the wings while on display.

810_3_detail of back of glass to show paint

The verso of a bat specimen mounted to an external glass plate.  AMNH/F. Ritchie

Many of the bats encountered in the survey had glass eyes and an articulated mouth, a metal wire armature in their wings, and were previously exhibited. For these reasons, we decided they were akin to other mammal mounts and included them in our survey. Half-mounts (also known as shoulder or trophy mounts) were also considered taxidermy, even though the whole animal isn’t represented because the preserved hide is still arranged to mimic a living pose.

 

Taxidermy Materials and Methods

In order to accurately identify the technology and materials used to create the mounts and to appropriately describe the damages we observed, we researched historical taxidermy practices. The choices the taxidermist makes can have an important impact on the condition of the object.

743_2_detail of split ear with earliner

Splitting skin around a rigid ear liner.  AMNH/F. Ritchie

If the internal manikin is made of excelsior or “wood wool” (slivers of wood, a common material from the late 19th and early 20th century), it will move in response to fluctuations in environmental conditions just as the mounted hide around it does. This movement can eventually cause tension or tears, and loosen the hide from the manikin. Conversely, if the manikin is too rigid, the hide may shrink over time and split open around the internal support.

 

 

 

Small copper-alloy pins added to hold fingers in place can react with the skin to form a waxy-green corrosion product called copper stearate. The corrosion can stain surrounding skin and hair, and can be difficult to remove.

annotated

Waxy green (most likely copper (II) stearate) corrosion on the pins that hold small fingers into place on a display branch. Red arrows indicate areas of corrosion.  AMNH/F. Ritchie

Some glass eyes can also exhibit an inherent deterioration known as “glass disease.” The cloudy appearance or even crizzling (fine cracking) occurs because of a breakdown of the chemical composition of the glass, often exacerbated by contact with skin. Once the disease begins it can only be slowed, not stopped.

735_3_detail of crack in eye

A crack in the glass eye of a specimen.  AMNH/F. Ritchie

860_3_detail of cloudy eyes

White accretions covering the glass eyes of a specimen, possibly glass disease.  AMNH/F. Ritchie

A future blog post will discuss taxidermy methods in more detail. In the meantime, check out the book Windows on Nature, written by longtime Museum exhibition project manager Stephen Quinn.

Here is a selection of some of the most interesting taxidermy specimens that we came across during our survey.

One of the oldest specimens that we assessed was an agouti that was collected in 1843, before the Museum was founded.

1058_1_overall

Image  AMNH/F. Ritchie

The largest mount was an elephant seal that is so large it must be stored in the Museum’s special large species room.

921_1_overall

Image  AMNH/F. Ritchie

The smallest taxidermy specimen was a harvest mouse.

1000_1_overall

Image  AMNH/F. Ritchie

The most unexpected specimen (for a North American conservator) was a platypus.

platypus

Image  AMNH/F. Ritchie

The exceptionally skilled execution of historical taxidermy techniques is exemplified by some of the small mammals, like squirrels, that were mounted in dynamic positions. This specimen was acquired through one of the founding collections (Verreaux).

937_1_overall

Image  AMNH/F. Ritchie

A Horse of a Different Color – researching colorants for recoloring taxidermy

For the 2011-2012 renovation of the Bernard Family Hall of North American Mammals dioramas, we were limited by the need for high lightfastness (resistance to fading), in situ treatment considerations, health and safety requirements, and reversibility/retreatability, so the project conservators looked to materials already in use in our profession (see previous posts for more details on this project). The Orasol® dyes seemed like a good alternative to the acrylic paint favored by the project taxidermist. Orasol® dyes (Ciba-Geigy; currently marketed by BASF for coatings and printing inks) are commercially available metal complex dyes that cannot be dissolved in water, but can be dissolved in many common organic solvents such as ethanol. They can be applied without salts or peroxides (which can be acidic), and require no rinsing, making them useful for in situ treatment. They are manufactured in a palette of 26 colors, which was enough to mix the range of tones needed for the North American Mammals. They are also generally approved by the conservation community and are commonly used in furniture and wood stains, as well as for tinting epoxy and other resins used for fills.

A word on dyes:

A dye is a substance that has an affinity to the substrate (in our case, the hair of the taxidermy mount) to which it is applied. In contrast, a pigment is generally insoluble and has no affinity for the substrate.

A typical dye molecule is composed of different chemical groups, each responsible for a specific property of the dye:

  1. Chromophore – color producing portion
  1. Auxochrome – influences the intensity of the color and provides the site at which the dye chemically bonds with the fiber (hydrogen, ionic, or dipole-dipole interactions with the substrate).
  1. Solubilizing group – allows the dye molecule to be soluble in a given solvent so it is capable of reacting with the fiber.
Typical dye molecule (from Synthetic Dyes for Natural Fibers. Knutson, Linda. 1982)

Typical dye molecule (from Synthetic Dyes for Natural Fibers, Linda Knutson. 1982)

Metal complex dyes are made of a transition metal ion such as chromium, copper, or cobalt complexed to two symmetrical dye molecules (chromophore and auxochrome). In general, members of this group have better lightfastness (resistance to fading) compared to other dyes due to the stability of the chelated complex and their large particle size; this, along with their working properties, has been the basis for their past use in conservation.

To determine if the dyes met all of our needs for the project, we developed some tests to compare the acrylic paints to the Orasol® dyes. The conservators worked closely with the taxidermist and partnered with outside conservation scientists to test the materials against these necessary criteria: minimal physical alteration to the hairs, retreatability/reversibility, and high lightfastness.

The physical appearance of bison hair samples colored with acrylic paint and ones colored using Orasol® dyes was examined using normal light as well as scanning electron microscopy (SEM). At first look, all of the colored samples appeared somewhat similar. The acrylic paints produced a matted and stiff feel, whereas the Orasol® dyes produced a more natural look and feel. The SEM images showed us that the binder in the acrylic paints covered the hair cuticle unevenly, creating a non-cohesive coating around the hair with some visible peeling and lifting. The Orasol® dyes were only just visible on the hair fibers and did not appear to cover or coat the hair shaft.

The surface of bison hairs imaged using scanning electron microscopy. From left to right: control (no colorant), acrylic paint, Orasol dye.

The surface of bison hairs imaged using scanning electron microscopy. From left to right: control (no colorant), acrylic paint, Orasol dye.

The taxidermist also found that the Orasol® dyes could be reduced or removed entirely when wiped or rinsed with ethanol after application. Although initially taken aback by this revelation, we quickly recognized the potential for reversibility, as well as the ability to produce special effects, such as localized reduction or removal of color to achieve special effects.

Project taxidermist reduces dye from a practice skin.

Project taxidermist George Dante reduces dye from a practice skin.

Metal complex dyes are generally regarded as having a high lightfastness. However, chromophore and auxochrome structures vary, making some dye colors more susceptible to fading. In their product literature, the manufacturer reports a definite range in both lightfastness and solubility from color to color.

Orasol dye lightfastness ratings according to manufacturer.

Orasol dye lightfastness ratings according to manufacturer.

These ratings are based on their use in printing ink, and the tests were conducted with two different binders (nitrocellulose and vinyl acetate) which produced significantly different results. To be able to judge the lightfastness of the Orasol® dyes when used on taxidermy, it was necessary to conduct our own tests without any binding media.

 The lightfastness of the dyes was tested using accelerated light-aging following the ASTM D4303 Standard Test Methods for Lightfastness of Colorants Used in Artists’ Coloring Materials. Test swatches were produced by airbrushing a 1% solution of dye dissolved in ethanol onto unbleached 100% wool as well as swatches of bleached bison fur. As a flat substrate of keratin fibers, the wool textile was chosen as a reasonable substrate to measure color changes using a spectrophotometer. Details about the testing procedure will not be listed here, but will be covered in subsequent posts as continued lightfastness testing is part of the current research program.

Conservation Fellows Julia Sybalsky and Rebecca Pollak prep swatches of Orasol dye for testing.

Conservation Fellows Julia Sybalsky and Rebecca Pollak prep swatches of Orasol dye for testing.

The ASTM protocol requires exposure of test materials to a broad spectrum of light that includes ultraviolet (UV) radiation. Since new lights in the diorama are filtered to exclude this particularly damaging light, the test helped us develop a worst-case scenario for assessing the lightfastness of the dyes.

Real-time monitoring of cumulative light exposure is continuing inside the bison diorama. Orasol dyes are exposed in situ alongside Blue Wool reference standards out of sight of visitors. At the same time, portions of the bison have been sprayed with dye mixtures and masked to permit direct comparison of exposed and unexposed areas of restoration.

Strategically placed dyed swatches and a blue wool card were placed inside the bison diorama (hidden from view), and sections of the dyed bison were covered for side-by-side comparison.

Strategically placed dyed swatches and a blue wool card were placed inside the bison diorama (hidden from view), and sections of the dyed bison were covered for side-by-side comparison.

Our lightfastness tests identified the most stable of the dye colors, allowing us to be picky about which shades could be used for the diorama taxidermy. The reversibility and retreatability of the dyes also played a major factor when deciding to use them on specimens in dioramas with higher light levels, with the understanding that fading will occur in time. The AMNH conservation and exhibition team was able to successfully recolor many of the faded specimens in the Bernard Family Hall of North American Mammals.

Coyote, before and after recoloring.

Coyote, before and after recoloring.

The dye research we did as part of the renovation generated numerous new questions, which fell into three main topics:

Lightfastness – While our previous testing did effectively establish a lightfastness ranking among the Orasol colors, it didn’t answer one of the questions we were asked the most often – “Ok, we know that the dyes in the brighter dioramas are eventually going to fade… how long will they last?” By developing a test procedure that mirrors the UV-filtered lighting environment in the dioramas , we will get enough information to be able to create a probable lifespan for these materials when used in treatment.

Penetration/Fixation – While the ease of dye removal was beneficial in the 2011-2012 recoloring treatments, in other contexts you might want a greater fixation or penetration of the dye. We want to understand ways we could achieve and manipulate that “fixability”, as well as knowing if those variations impact the dyes working properties and lightfastness.

Substrate Degradation – Finally, we want to better understand whether or not the use of recoloring materials like the Orasol dyes causes the colored animal hairs to degrade faster than normal, or do they act as a protectant and slow down light damage?

These topics acted as a starting point for the research plan for the current project: Recoloring Faded Taxidermy: Research into the Properties and Applicability of Dye Materials for Conservation Treatment, the details of which will have to wait until the next post!

Renovation of the Bernard Family Hall of North American Mammals Part II: Unique Challenges in Restoring Faded Taxidermy

Badly in need of restoration after over 70 years of exposure to high light levels, temperatures, and fluctuations in relative humidity, the iconic habitat dioramas in the Bernard Family Hall of North American Mammals were renovated in 2011-12. Among the most significant problems was fading observed in the taxidermy specimens.

Some members of the diorama renovation team: Museum Exhibition Project Manager: Stephen Quinn. Museum conservators: Judith Levinson, Lisa Elkin, Elizabeth Nunan. Conservation Fellows: Julia Sybalsky, Bethany Palumbo. Museum artists: Richard Webber, Joi Bittle-Knight. Project Taxidermist: George Dante AMNH/E.Nunan

Some members of the diorama renovation team: (clockwise from upper left) Director of Natural Science Conservation Lisa Elkin, Museum Exhibition Project Manager Stephen Quinn, Assistant Conservator Elizabeth Nunan, Project Taxidermist George Dante, Director of Anthropology Conservation Judith Levinson, Museum exhibit preparator Joi Bittle-Knight, Museum exhibit preparator Richard Webber, Conservation Fellows Julia Sybalsky and Bethany Palumbo.
©AMNH/E.Nunan

 

The diorama renovation team (curators, conservators and conservation scientists, exhibit preparators, taxidermist) faced a number of challenges in choosing an appropriate colorant to restore the faded taxidermy in the dioramas. One of the most immediate difficulties was the short project timeline, which limited the type and extent of research that could be done. There was only one year for all of the renovation work to take place, from start to finish, with 45 dioramas and over 100 taxidermy specimens. A maximum of only 2 months within that year could be allotted for research and testing of possible colorants for the faded mammals.

In addition to the limited research period, there were several other critical factors that restricted the materials that could be considered for re-coloring.

High light levels

Even with the new energy efficient lights, the naturalistic lighting design in each diorama did not allow us to reduce light levels to what is generally considered acceptable for museum collections. The highest recorded light levels are 65 footcandles (fc) on the top of the mountain goat and 50 fc at the head of the cow in the bison diorama, whereas the recommended level for fur at the Museum is 5 foot candles. Therefore, even with somewhat reduced light exposure, it was clear from the outset that any colorant considered for use would have to have high light-fastness ratings to limit fading under the harsh diorama conditions.

Light levels in the Mountain Goat diorama. ©AMNH/E.Nunan

Light levels in the Mountain Goat diorama.
©AMNH/E.Nunan

Treatment in situ

Because the larger taxidermy mounts had to be treated in situ, custom built platforms to avoid crushing the fragile foreground materials were required to provide safe access. Washing or rinsing excess coloring materials from the specimens would not be possible. Ease of preparation, application, and clean up were all important considerations when choosing a colorant.

 Installing platforms inside dioramas in the Bernard Family Hall of North American Mammals ©AMNH/E.Nunan


Installing platforms inside dioramas in the Bernard Family Hall of North American Mammals
©AMNH/E.Nunan

Health and Safety

The use of certain solvents was restricted because possibilities for effective fume extraction inside the dioramas were limited. Additionally, because half of the exhibition hall was required to remain open to the public over the duration of the project, control of solvent fumes was critical.

 Project taxidermist and artist wearing respirators during recoloring. ©AMNH/E.Nunan


Project taxidermist and artist wearing respirators during recoloring.
©AMNH/E.Nunan

Reversibility/Retreatability

Because the dioramas would probably not be renovated again for at least 25 years due to associated costs, favorable aging characteristics, reversibility and ease of future retreatment were important factors in choosing recoloring materials. The colorants selected should not cause the hairs to clump or mat, and if not fully reversible they should not prevent future recoloring projects on these irreplaceable taxidermy mounts.

Investigation of the conservation literature on contemporary methods for coloring taxidermy revealed few references. Through personal correspondence, some museums reported success recoloring some of their taxidermy mounts using Clairol commercial hair dye, but their situation allowed for the removal of the specimens from the diorama for treatment, and the long-term stability of those dyes are not known. Other recent studies investigated fiber-reactive dyes for feather recoloring, but the approach was ruled out due to concerns about water-based treatments having an adverse effect on the tanned taxidermy hides, as well as the long-term effects of the acidic or basic dye residues.

Water and solvent-based acrylic paints are commonly used among contemporary taxidermists. When used inside habitat dioramas, reversing acrylic paints for retreatment would be very problematic. Also, due to their low glass transition temperature, it is possible that the paints would remain soft in the heat of the diorama lamps, entrapping dust and hindering future cleaning.

The project taxidermist’s familiarity with commercially available acrylic paints and his skill with airbrushing played a tremendous factor in determining what other colorants would be considered.

 An echidna mount recolored by taxidermists at Wildlife Preservations, Inc using acrylic airbrush paints. ©G. Dante/Wildlife Preservations, Inc.


An echidna mount restored and recolored by taxidermists at Wildlife Preservations, Inc using acrylic airbrush paints.
©G. Dante/Wildlife Preservations, Inc.

His method for restoring faded specimens consisted of layered airbrush applications with constant grooming throughout the process in order to control the hue and intensity of the color. Any alternative colorant would need to be applied in a similar manner, in order to fully utilize the taxidermist’s skill in this method, and to meet the tight project deadline.

 Taxidermist George Dante recoloring a bison mount. ©AMNH/E.Nunan


Taxidermist George Dante recoloring a bison mount.
©AMNH/E.Nunan

The next post will discuss the colorants that the research team chose, as well as the tests conducted to determine whether they met the necessary criteria for minimal alteration to hairs, high lightfastness, and retreatability/reversibility.

Introducing the Recoloring Taxidermy Research Project

In 2013, the American Museum of Natural History and Yale University’s Institute for the Preservation of Cultural Heritage and the Peabody Museum of Natural History were awarded an Institute for Museum and Library Services‘ (IMLS) National Leadership Grant to fund a three-year project devoted to the development of best practices for recoloring faded mammal taxidermy mounts, especially those in habitat dioramas: Recoloring Faded Taxidermy: Research into the Properties and Applicability of Dye Materials for Conservation Treatment.

After years of display under bright lights, and harsh temperatures and humidity, many taxidermy mounts have become discolored and faded. Techniques for restoring the lost colors of damaged natural history collections are limited and under-researched. This knowledge gap puts at risk collections of great educational value, especially as some historical specimens represent species that are endangered, if not already extinct.

Image

The project conservators are interested in developing re-coloring methods that would minimally alter the texture or sheen of hair and fur, and could be as reversible or re-treatable as possible.

This research will foster cross-disciplinary partnerships between conservators and scientists with varying forms of expertise, helping to bridge the institutional gap between natural history, art, and history museums and collections.

The IMLS-funded project will build upon promising results from a pilot study conducted by the Museum into the use of certain dyes, such as those used in certain specialized printing inks, to recolor taxidermy hair and fur. The next few posts will present the results of the restoration project that resulted in the dramatic restoration of the faded specimens in the habitat dioramas in the Museum’s Bernard Family Hall of North American Mammals.

Image

 

The findings from the study, which the Museum conservators presented at 2012 annual meetings of the Society for the Preservation of Natural History Collections (SPNHC) and the American Institute for Conservation (AIC) and published in the October 2012 International Committee of Museum, Natural History Collections Working Group Newsletter, were received with immense interest by practitioners and researchers alike. Together with results from a national survey among conservation professionals, it was evident that there was a strong need for comprehensive research to explore additional materials and discover an appropriate method for recoloring faded taxidermy in museum collections.