Case Study: Flying Squirrel Treatment

Another of the specimens treated as part of our preparation for our Care of Historic Mammalian Taxidermy workshop at the Society for the Preservation of Natural History Collections (SPNHC) 2017 annual meeting was a taxidermy giant red flying squirrel. Project Intern Logan Kursh executed the treatment.

TearRepairProcess

Conservation Intern Logan Kursh performing conservation treatment on a flying squirrel taxidermy mount. ©AMNH /F. Ritchie

There was little data available about the date or location where this specimen was collected, or about the taxidermist who prepared it. However, an examination of the specimen indicated that it was likely a nineteenth century mount, prepared using the binding method.

The specimen suffered from a number of structural and aesthetic issues. The treatment of many of these condition issues is detailed in a poster titled, “Strategies for the Conservation and Storage of Taxidermy:  Flying Squirrel Case Study” that was prepared for the SPNHC 2017 annual meeting in June 2017. Access the poster here:

SPNHC_2017_Squirrel Poster_Logan Kursh

The poster did not address the restoration of the squirrel’s snout, however, so that work is explained below.


Skin on the face and around the squirrel’s snout is thin and delicate. Like all skin in taxidermy, this hairless skin dried out and discolored after death. Taxidermists typically address this with the use of “finishing materials” such as wax and paint to add vitality. The finishing materials degrade over time, giving the specimen an unnatural appearance.

flying squirrel before treatment

Flying squirrel before treatment. Note the desiccated deformed nose. ©AMNH /L. Kursh

In the case of the squirrel, the nose appeared flat and desiccated. The skin had discolored, and there appeared to be some local fur loss. Examination of other giant red flying squirrels in our collection and reference images of squirrels in life confirmed that the specimen’s appearance was not an accurate reflection of the species in life. With the approval of the Mammalogy Department, we decided to craft a reversible overlay for the squirrel’s snout from reference images using well-understood conservation materials.

The nose and upper lips of the specimen were restored using an overlay made from Paraloid F-10 bulked with glass microballoons. Paraloid F-10 is a thermoplastic acrylic resin. It was chosen for this application because it adheres well to wax and has known ageing properties. The Paraloid F-10 mixture was spread onto a piece of silicone-release Mylar and toned slightly with dry pigment, then shaped with a microspatula based on reference images. The overlay was allowed to dry for several hours and reshaped as it slumped.

flying squirrel during treatment

Flying squirrel during treatment. The white fill material has been applied on top of the original surface and shaped to reconstruct the nose. ©AMNH /L. Kursh

To ensure complete reversibility, the overlay was attached to the specimen over a barrier layer of Paraloid B72 in acetone. Paraloid B72 is a stable thermoplastic acrylic resin and is a common art conservation adhesive in many different applications. Minor adjustments to the shape of the overlay were made, and the overlay was allowed to dry overnight. Once dry, further adjustments to the shape were made with a scalpel in consultation with expertise from the Mammalogy Department.

flying squirrel during treatment

Flying squirrel during treatment. The nose has been reconstructed and the white fill material toned brown with paint. The next step is to add hairs to integrate the fill with surrounding areas. ©AMNH /L. Kursh

flying squirrel during treatment

Flying squirrel during the final treatment step – the addition of hair on the toned fill of the nose. ©AMNH /L. Kursh

The overlay was toned with acrylic paint based on available references. Rabbit fur was flocked onto the overlay with Lascaux 498HV. Lascaux 498HV is a thermoplastic acrylic resin that dries flexible and is reversible with heat.

After treatment the squirrel’s nose appears more life-like and integrates with surrounding features.

flying squirrel after treatment

Flying squirrel after treatment. Note the reconstructed nose. ©AMNH /L. Kursh

For details about other aspects of the treatment of this specimen, be sure to check out the SPNHC poster. SPNHC_2017_Squirrel Poster_Logan Kursh

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Case Study: Lemur Mount Treatment Part 2: Treatment

Before Treatment of lemur.

Before treatment of lemur taxidermy mount. ©AMNH /C. Richeson

In addition to thorough condition examination and photographic documentation, conservation treatment decisions should begin with a clear proposal to be approved by Collections Managers, Curators, or other stakeholders prior to beginning hands-on work. Caitlin submitted the following treatment proposal to the Mammalogy Department for the treatment of the lemur mount. 


Treatment Proposal

  1. Use a HEPA-filtered variable-suction vacuum fitted with micro-attachments to remove dust from the specimen.
  2. Use wet cleaning solution to remove or reduce other surface accretions, as needed after vacuuming.
  3. Attach the detached proper left (PL) ear using an appropriate adhesive system.
  4. Inpaint the repair to visually integrate it with the mount.
  5. Attach the detached PL hand using an adhesive system, with a pin if necessary.
  6. Create fills for the fur losses using compatible materials.
  7. Inpaint and/or fill losses and deformations on the nose and face.

Once the treatment proposal was approved, she carried out the conservation treatment and recorded each step (described below). The reports and photographs generated during conservation treatments are archived in the Museum for future reference for conservators, researchers, and department staff. 


Treatment Record

Treatment began with surface cleaning the specimen overall using a variable speed HEPA vacuum at a low setting with micro attachments and an eyebrow comb.

In the process, hairs around the seam matted with a dark brown/yellow accretion  were exposed. Solvent tests were conducted using cotton swabs dampened with three cleaning solutions: a 1:1 mixture of deionized (DI) water and ethanol; mineral spirits; and a 1% solution of Surfynol 61 dissolved into a 1:1 mixture of DI water and ethanol. Although each solvent removed some of the brown/yellow accretion, mineral spirits was most effective. The accretion removal process began by placing small triangles of cotton blotter paper under the hairs. We then brushed mineral spirits onto the accretion. The blotter paper served to absorb the solvent and the loosened accretion. The white blotter paper also acted as a visual guide to ensure that the hairs were sufficiently cleaned of the dark accretion before moving to the next section. Once the hair was cleaned and dry, the specimen was gently groomed using an eyebrow comb.

during treatment lemur

During treatment of the lemur taxidermy mount. Note the right side of the torso has been cleaned and groomed, while the left side has not. ©AMNH /C. Richeson

Next we humidified the proper left (PL) ear and the detached fragment because both of them were desiccated and curled inward. The humidification was done using a small vapor chamber created from in a layer of Gore-Tex (a semi-permeable membrane that allows vapor through, but not water), a piece of blotter paper dampened with DI water, and a thin polyethylene bag. The Gore-Tex barrier was laid over the skin and the dampened blotter was secured on top of the Gore-Tex using a hair clip. A polyethylene bag was then placed on top of both layers to seal them into a chamber. The skin was checked approximately every 15 minutes for the duration of one hour until it was relaxed and pliable enough to be re-formed. The humidified skin was re-shaped and allowed to dry in proper alignment with the help of a rigid piece of dry blotter paper.

during treatment lemur

During humidification of the broken proper left hand of a taxidermy lemur. The humidification allows the skin to realign for reattachment of the hand. ©AMNH /C. Richeson

during treatment lemur

During treatment of the taxidermy lemur. Detached proper left hand in a water vapor humidification chamber to align the edges for reattachment. ©AMNH /C. Richeson

To reattach the ear fragment we used BEVA 371 film. Small strips of film were tucked between the layers of the epidermis on both the fragment and attached ear. The film was then warmed using a variable heat spatula, which set the adhesive. To protect the skin from direct heat contact, silicone release Mylar was used as an interleave.

Reattachment of the PL hand required use of Japanese tissue paper lining impregnated with BEVA 371. A bamboo skewer bent at a 45° angle was used to help apply pressure to the tissue while applying the heat spatula to the opposite side.

Losses on the repaired hand were filled using a small piece of coyote hide with bleached and toned fur. Faber Castell Pitt artist pens were used for toning, and excess ink was removed with blotter paper. The fill was adhered with BEVA 371 film.

after treatment lemur

After treatment photos of lemur. ©AMNH /C. Richeson

To restore the damaged nose, we sculpted a reconstruction using Paraloid F-10 heavily bulked with glass microballoons. The bulked resin was cast out onto a sheet of silicone release Mylar into the desired shape and thickness. After two days the bulked resin was pliable, but not sticky, and could be shaped without slumping. The reconstruction was formed to fit on top of the existing damaged nose. Once hard, it was smoothed using micromesh and toned with Golden acrylic paint. It it held in position by friction, and can easily be lifted/removed with a microspatula or bamboo skewer.

after treatment lemur taxidermy mount

After treatment of lemur taxidermy mount. ©AMNH /C. Richeson

Finally, we constructed a new storage mount for the specimen. The specimen was previously stored in an upright position with an L-shaped storage base. This orientation was optimum for the the specimen, as it placed the least amount of stress on the specimen and posed the least risk to the disruption of the hair, but the limited space in collection storage required a different solution. After confirming that the habitat base could be altered in a non-visible way, we drilled two small holes into the display branch, inserted brass rods, and positioned the rods into a plywood base, elevating the specimen slightly above the board. An ethafoam block supports the proper right hand of the specimen and branch. The new storage solution allows the specimen to be stored horizontally, while protecting the fur from being crushed.

 

Case Study: Lemur Mount Treatment Part 1: Condition Examination

In addition to testing the stability of metal-complex dyes, we have been studying condition issues facing historic taxidermy collections (see our previous posts on the Mammalogy condition survey) and performing conservation treatments on selected specimens. These treatments stabilized important mounts and served as case studies for a workshop on the Care of Historic Mammalian Taxidermy at the 2017 Denver meeting of the Society for the Preservation of Natural History Collections (SPNHC).

Before Treatment of lemur.

Before treatment of lemur taxidermy mount. ©AMNH /C. Richeson

In one of these Case Studies, project intern Caitlin Richeson treated a damaged red-fronted brown lemur (Eulemur rufus) taxidermy mount. Its catalog number suggests that it was acquired soon after the Museum was formed in the late 19th century. This post and the next one will provide some of the details of that treatment.

All conservation treatments should begin with thorough documentation: an object description, condition examination, and photography. Caitlin’s project provides a good example of what that documentation may look like for a piece of taxidermy.


Object Identification: A full-body taxidermy mount of a female red-dronted lemur (Eulemur rufus) mounted on a habitat base constructed from a tree branch.

 

Description
The specimen is constructed around a composite manikin that is visible in several locations due to previous damages. The manikin is composed of wood wool (thin wood shavings traditionally made of poplar, pine, or spruce) bound to recreate the musculature form of the specimen; cotton batting used to bulk appendages such as the hands; and a metal armature used to provide rigid structural support. Appendages such as the hands and feet still contain original skeletal materials. The nose, snout, and eyelids are shaped from a soft black material, likely a pigmented wax.

The specimen is attached to the base with ferrous metal wires at three points: the proper right palm, the proper right foot, and the proper left foot. The wires penetrate the palm and feet of the specimen as well as the habitat base where they have been secured to the base by bending at a 90-degree angle.  The specimen is mounted in a standing position gripping the habitat base with the proper right (PR) hand and both feet.

There is a paper specimen label tied to the proper right ankle, which contains taxonomic information in two separate campaigns of writing. There is also a metal plate attached to the habitat base located on the front of the branch.  The plate is inscribed with the catalogue number and attached to the branch with two tacks. There is another metal tag tied with a thin metal wire around the PR wrist of the specimen, also stamped with the catalog number.

Condition
The specimen is in fair condition. It is structurally stable; however, there are two detached elements, several areas of fur loss, tears and cracks/splits in the hide, which contribute to the overall instability of the specimen. In addition, the specimen is covered in a layer of light grey dust and grime.

Hide/Manikin:

  • A portion of the proper left (PL) hand is detached from the specimen. The detached hand consists of the hide and four digits, but excludes the thumb, which remains attached to the specimen. The detached hand has several cracks/splits in the hide and a large loss on the palm side, exposing the interior construction. The PL ear of the specimen is also detached and there are small areas of unrecovered loss.

Before Treatment of lemur detached proper left hand.

Before Treatment of lemur detached proper left hand.

Before treatment of lemur taxidermy mount. Proper left detached hand. ©AMNH /C. Richeson

  • On the lower back at both the PR and PL sides there several moderately large stable tears in the skin of the lower torso, which expose the wood wool manikin below. There is also a minor split located at the PR side of the vent. Although the skin is slightly out of plane, it remains somewhat pliable and can be pressed back into place with gentle pressure.
  • There is a small circular area of abrasion on the back of the PR hand.

Finishing Materials:

  • The material used to finish the nose of the specimen has sustained localized losses and a dent on the PL side. The eyelids, which are made from the same finishing material, have also been deformed.
    Before Treatment of lemur. Detail of nose with missing wax.

    Before treatment of lemur taxidermy mount. Note the loss of finishing material on the nose and the loss of skin on the ear. ©AMNH /C. Richeson

    Before Treatment of lemur. Detail of nose with missing wax.

    Before treatment of lemur taxidermy mount. Note the loss of finishing material on the nose. ©AMNH /C. Richeson

Fur:

  • The fur of the specimen has discolored to a light yellow-brown color, having lost its natural variation in red, brown, and black colors that are representative of the species.
  • There are several areas of fur loss located on the mount. The first is a a substantial loss of fur on the chin and underside of the snout. This species is identifiable by its characteristic “beard”, and thus the fur loss in this area detracts from the accurate representation of the species. There are also small losses associated with the detached PL hand and at the coccyx.
  • There are also beige accretions on the fur, primarily located along the seam at the center of the torso, and an overall layer of moderate dust accumulation on the fur.

Display Base (branch):

  • The specimen is well-secured to the tree branch habitat base, which appears to be in good condition. When examined in ultraviolet light, the base fluoresced a milky yellow/green color, and appears to have been coated.

After completing this type of photographic and written documentation, the conservator then submits a proposed treatment to the Collections Manager and/or Curator for approval. Follow along with the progress of this treatment in the next post.

 

 

Surveying Historic Taxidermy Part 3: Results

Our condition survey of historic mammalian taxidermy in the American Museum of Natural History’s Department of Mammalogy (see previous post), supplied an understanding of the most common condition issues affecting them, and clearly displayed their probable causes.

Cracks, Splits, and Dust: Responses to Environment

649_3_detail of crack_split on tail

Split in the hide at the base of a specimen’s tail.  AMNH/F. Ritchie

It is not unusual to find cracks and splits in historic taxidermy mounts. The organic materials comprising taxidermy (hide, skin, horn, teeth, manikin materials, etc.) will expand and contract as a response to changes in relative humidity and temperature in the environment. This is similar to the way one’s hair increases in volume during more humid days, but is flat on dry ones. If there are small tears or cracks in the hide, they may open up during these fluctuations and become bigger. Much of the historic taxidermy in the Museum is more than 100 years old, meaning it was acquired well before the invention of modern environmental control systems in use today. We were not surprised to discover cracks and splits in hides, teeth, and other organic components.

Akeley elephants_dust slide_1

Dust accumulation on a glass slide that was placed in a museum public hall for one year.  AMNH/F. Ritchie

Dust may seem innocuous, but it is a serious concern for taxidermy. “Dust” can be anything from lint or dried skin cells to coal dust or other sources of air pollution. These small particles can be abrasive, oily, and/or hygroscopic, meaning that they attract moisture that creates localized varying microenvironments on the surface. Furthermore, accumulated dust detracts from the perceived vitality of a specimen and alters its apparent color; even when the dust itself presents only a minor risk, the aesthetic considerations of display may require investing resources in cleaning methods that could introduce more significant risks like hair breakage, slippage, staining, or disruption of previous recoloring treatments. Most of the specimens surveyed were stored in enclosed storage cabinets or covered by protective plastic sheeting. Mounts in open storage, however, are particularly vulnerable to dust accumulation.

 

Breaks and Loss: Responses to Handling

As mounted skins age, they often become brittle and more sensitive to damage by handling. During the survey the conservators noted broken limbs, detached pieces, and other signs of damage that may have occurred as these objects were handled for various purposes over their long lives. Some taxidermy may have suffered these damages even before entering into the collections. Taxidermy is also vulnerable to damages due to handling during the exhibit installation and de-installation processes, during movement of the collections, and during research. For these reasons, our collections staff follows detailed guidelines that are specifically intended to mitigate these risks.

650_2_detail of broken foot

Detached toes that may have occurred during the de-installation of this specimen. Detached pieces are stored in the same location as the specimen until they can be repaired/conserved.  AMNH/F. Ritchie

Fading: Responses to Light Exposure

Discoloration and fading in fur is minimized by dark storage. Some taxidermy specimens surveyed were previously on display at the Museum and now exhibit light-induced discoloration and fading, not unlike that seen in the Bernard Family Hall of North American Mammals before its recent renovation. Comparing these discolored examples to the unfaded study skins in adjacent storage can be very useful in determining the degree of fade or discoloration. Where they can be used appropriately, re-coloring techniques have the potential to restore the naturalistic appearance of faded specimens and extend the possibilities for their use in dioramas or other exhibits.

fading example

Specimens of the same species – on the left, the taxidermy examples that were on display for a number of years and exhibit fading of the fur from light exposure. The unexposed unfaded (darker) study skins line the right side of the drawer.  AMNH/F. Ritchie

Other Condition Issues

Several other types of damage were reflected in our survey. These include loss of hair due to old, (currently inactive) pest activity; chemical deterioration of materials used in manikin construction or finishing work, such as rusting metal ear-liners or flaking paint; and structural issues in the base, such as loose attachment of the taxidermy mount and cracks in wood or plaster.

960_1_overall_1

Squirrel specimen that has lost the nut previously displayed in its mouth. Note also the area of loss of foliage on the display base (yellow area).  AMNH/F. Ritchie

Future Work

0421_0004

Project Conservator treating loose hide on a moose mount.  AMNH/J. Sybalsky

As the project continues, we will be working to stabilize and restore some of the specimens evaluated in our survey. Examples and case studies derived from these treatments will be shared in the various informational and training resources under development.

 

 

 

Surveying Historic Taxidermy Part 1: Goals and Parameters

Alongside the lightfastness testing described earlier in this blog, we are developing tools to support the efforts of other individuals and institutions seeking to preserve collections of historic mammalian taxidermy. To do this, we needed to deepen our understanding of the historic and modern materials and techniques used in creating these objects, the common condition issues affecting them, and methods of remediation, both historic and modern.

1194_2_detail face and mouth

Taxidermy viscacha specimen from the collection during condition surveying. (c) AMNH/F. Ritchie

Working toward these aims, we conducted an inventory and condition survey of taxidermy in storage in the Department of Mammalogy of the American Museum of Natural History. This survey was intended to accomplish the goals set out above with the added benefit of providing the department with a searchable, data driven inventory of the entire mammalian taxidermy collection. This kind of inventory can serve as a basis for planning and decisions related to collection management and storage, loans, exhibits, and associated conservation needs.

The Department of Mammalogy is one of four departments in the Museum’s Division of Vertebrate Zoology Division. The department’s collection comprises more than 420,000 specimens from around the world, although only a tiny fraction of those in storage are taxidermy mounts. This fraction still represents about half of the mammal taxidermy at the Museum, with the other half on permanent display. These numbers should not be surprising: museum-quality taxidermy is costly to produce and limited in its scientific uses compared to materials such as study skins or skeletons. Instead, taxidermy is valued primarily for display, so it has been produced in relatively small numbers for specific exhibits over the years. Thus, the percentage of specimens on display versus in storage is much higher for taxidermy than it is for other materials that are more often used in scientific research. Among the Museum’s mammal taxidermy holdings are numerous examples from the founding collections that were acquired in 1869 and are now approaching 150 years old. How are these specimens holding up after so many years?

Caitlin_bats

Project intern Caitlin Richeson examining taxidermy fruit bats in collection storage. (c) AMNH/F. Ritchie

Over a period of four months we spent an average of two to three days per week surveying. We worked around visiting researchers and staff using temporary photography and examination stations in each room. Each specimen took five to 10 minutes to assess, depending on its complexity and accessibility. After opening every storage cabinet and pulling out every drawer to ensure that no specimen was overlooked, we assessed approximately 635 individual mounts in 30 mammalogy-collection storage spaces.

Fran_bat

Project conservator Fran Ritchie examining a specimen at a temporary surveying station in collection storage. (c) AMNH/K. McCauley

Using a custom-built database, we tailored our survey parameters to record identifying information for each specimen, an assessment of its condition, and recommendations for treatment. If desired, the data collected can be exported in CSV and PDF file formats and then imported or attached to records in other existing databases, such as the EMu database system used by the Museum’s Division of Vertebrate Zoology.

Data gathered for each specimen included ‘identifying information’ such as:

  • Specimen Description – Basic taxonomic and locality information, as well as notes about special historical, scientific, or ecological significance
  • Current Storage Location – Building, floor, room, cabinet number(s), and cabinet label(s)
  • Transcriptions – Data from all labels and inscriptions, including taxonomy, catalog and other numbers, and other scientific or historical details
  • Digital Photograph(s) – An overall identifying photograph as well as details of specific condition or preparation issues, when appropriate
database_mock

Survey database example entry (not actual specimen in the collection).

We evaluated the condition of each specimen, looking closely at the following elements:

  • Internal armature
  • Skin/hide
  • Fur/hair
  • Antlers/horns/hooves/nails/claws/teeth
  • Eyes
  • Finishing materials (for sculpting lips, nose, etc.)
  • Base
  • Specimen label
Kelly_workspace

Summer intern Kelly McCauley using the survey database to examine a specimen in collection storage. Note the grey photography paper used to photograph each specimen. (c) AMNH/F. Ritchie

Each specimen was given an overall condition summary, identifying it as Excellent, Good, Fair, or Poor, and further noting whether it is Stable or Unstable, based on the likelihood of existing damage worsening if left untreated.

In the final section of our survey, we recorded the nature and extent of any conservation treatment that would be required to make the specimen stable or suitable for exhibit, such as skin repairs, reconstruction, general grooming, dry cleaning, etc.

Together, all of this documentation will be used to guide decisions about how best to manage, store, and exhibit historic mammal taxidermy at the Museum, while offering supporting resources for the preservation of similar collections at other museums or sites.

Our next post will reveal some of the unique examples that we discovered during the survey.

It’s All In the Preparation: Part 1

As earlier posts have mentioned, the first phase of our research aims to establish the lightfastness of the Orasol® and similar Sorasolve metal-complex solvent dyes in isolation‒ that is, in the absence of a binder, and without a chemically active substrate that could potentially influence the behavior of the dyes or interfere with the measurement of color change. To accomplish this we needed a substrate for the dye film that would not be altered physically or chemically by the accelerated aging exposure and would not interfere with our reflectance measurements (reflectance measurements will be discussed further in up-coming posts). The required substrate would need to be:

1.  Optically pure.

Any color or visual irregularities in a substrate would affect our color measurements, and impede an accurate calculation of the dyes’ lightfastness.

2. Durable.

The substrate needs to withstand a degree of handling throughout its use. For example, in one test cycle, the samples are measured for color change 8 times, in addition to before-, during-, and after-treatment photography.

3. Chemically inert.

The substrate must not be altered physically or chemically by the accelerated aging process, to ensure that it does not discolor (impeding accurate measurement of color change in the dye itself) or produce reaction products that could potentially alter the behavior of the dye.

Before making our final choice, we considered and rejected several candidates:

pink dye on wool

BASF dye Pink 478 (CIGN Solvent Red 127) sprayed on wool textile substrate. Although wool readily accepts dye, it was not chosen as the substrate because of its chemical instability during accelerated aging. Note also that the color of the dye is different depending on solvent. Solvent, top to bottom: acetone, ethyl acetate, ethanol, isopropanol, PGME. AMNH/F. Ritchie

Wool textile: inexpensive, readily available, and resilient to handling. It has the great benefit of accepting the dye in a manner very similar to the fur/hair on our taxidermy specimens because it is made from the same material, keratin fiber. However, it is not chemically inert, and is known to bleach or yellow during accelerated aging.

Acid-free paper: durable and inexpensive, but, like wool, is not chemically inert and may undergo color change or influence the stability of the applied dye. In addition, it accepts the dye solutions in a manner quite different from hair/fur, as they are readily absorbed deep into the sheet.

Glass slides or plates: much more chemically stable than wool or paper, though they may still produce reaction products in high temperatures and humidity. Dye applied to glass sits on the surface, similar to keratin fiber. Glass is inexpensive, but could be cleaned and reused if necessary. It is, of course, more fragile than wool or paper.

Ultimately we decided to use thin quartz plates, because they best fulfill our optical, physical, and chemical requirements for a substrate. Quartz plates consist of pure silicon dioxide (SiO2). They are not only optically pure (being transparent and colorless) and have a high damage threshold; they are also non-absorbent and reusable. However, as we came to appreciate, they are typically used in very sensitive research applications, which require high standards of dimensional exactness and chemical/optical purity. As such, they aren’t cheap. Finding affordable quartz plates was very challenging, and eventually took us to a Chinese company that was able to provide us with custom-cut plates that easily met the needs of our project, without the cost that accompanies the exacting standards required by other research applications.

Drawing on the procedure outlined in the ASTM D4303 standard, our testing of each dye solution and set of lighting conditions uses three replicate samples (A, B, and C). Two plates (A and B) are exposed in the aging chamber during the test cycle, and the third (C) is held in dark storage as a control. Throughout each test cycle, color measurements are taken periodically from each replicate. Each plate is measured in three locations, and these results are averaged to produce an overall measurement for that sample at that time index.

Having selected a transparent substrate, it was necessary for us to then identify a material to place behind our samples during our reflectance measurements and accelerated aging cycles. For the former, a standard white backing material was needed — something opaque (to eliminate any influence on the measurement from the tabletop or work surface behind this backing), and either durable or easily replaced. It would also need to be extremely white (i.e. with a uniform high reflectance throughout the visible spectrum) so that it would reflect the light transmitted through the sample back up into our reflectance spectrophotometer without distorting the spectrum of the dye. We chose to use plain white nitrocellulose membrane filters stacked three layers deep to ensure opacity. While a white ceramic tile could also have been used, we felt that the membrane filters would be more easily incorporated into the wooden jig that we are using to standardize our measurement locations.

jig with sample__1

Jig built for the project to hold quartz plate dye samples during color measurements. Note the white nitrocellulose film used to back samples. AMNH/F. Ritchie

For the same reason that a white backing material is helpful in color measurement, it would be problematic in our accelerated aging exposures: a white surface would act as a mirror, reflecting light from the xenon lamp that had already passed through the sample back up toward the plate. This would be exposing the dye films twice, once by direct exposure of the lamps, and a second time by reflected light from below, increasing the light exposure dose by some unknown percentage. This would make our determination of a rough equivalence between accelerated and real time aging periods in our dioramas more difficult. Eliminating the backing altogether would have the same effect: the plates would rest directly on our reflective aluminum sample holders. We needed to identify a material that would absorb the light transmitted through the sample plates but also would withstand the extreme environment within the accelerated aging chamber. We would need to use a black backing inside the chamber.

To realize this light-absorbing backing, we initially lined our aluminum sample holders with black archival matte board. We also added bumpers along the edges of the backing to create a small space for air circulation between the board and the plates, which helps with heat dissipation. Unfortunately, we discovered that the matte board generated a sticky condensate on the underside of the plates during aging. We altered our design to instead use black textile masks and corrugated blue board. These have proven to be free of the condensate problem of the matte board. The masks slowly fade during our exposures that include UV radiation, so we designed our sample mounts in such a way that new masks can be inserted when replacement is needed.

black panel_plate_holder

Clockwise: Quartz plate without dye, sample backing of black textile mask with cardboard bumpers covered in black textile mask, metal sample holder. AMNH/F. Ritchie

sample holders

Top: Dye samples resting on black backing. Bottom: Dye samples assembled in sample holder, ready for testing. AMNH/F. Ritchie

 

 

 

 

 

 

Part Two will describe how we prepare the quartz plate dye samples.

Accelerated Aging Chamber, Part 2

Troubleshooting

Conservation Intern, Associate Conservator, and Project Conservator working to troubleshoot an issue with the water purification system that occurred while this post was written. AMNH/F. Ritchie

Part 1 of our posts on accelerated aging instrumentation introduced the Q-SUN Xe-3 accelerated aging chamber. In this posting we describe some of the challenges we have experienced in installing and operating the machine; challenges which were unexpected and eye-opening. Problem-solving these situations has been such an important learning experience for us, demonstrating what taking on a project of this magnitude really entails.

Modifying the Lab

Our initial challenge was retrofitting the lab to accommodate the needs of the unit. In addition to electrical and plumbing adjustments to provide sufficient voltage, surge protection, purified water, and condensate drainage (all while retaining the ability to move the unit around the lab on its casters as needed), we had to install a ventilation hood over the machine with a fan and ductwork to vent its exhaust directly out of the building. This was necessary to limit the machine’s impact on the environment in the lab and adjacent offices, which otherwise became uncomfortably hot and cold respectively. The improved ventilation also allows the machine to cool itself much more efficiently, reducing both the noise and overall consumption of purified water – saving both our budget and our ears. We learned firsthand how important it is to moderate lab temperature when the HVAC system in the lab randomly failed and the machine was forced to stop because the chamber air rose to an unacceptable temperature. Luckily our maintenance staff provided the troubleshooting for this situation and the test cycle resumed within 24 hours.

Lesson: Make sure to understand completely the needs of a machine and its impact on day-today processes.

IMG_20151104_115246043

Ventilation hood and fan installed above the Q-SUN Xe 3 chamber to extract heat generated from the machine, helping maintain lab temperature. AMNH/F. Ritchie

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New ductwork installed to direct exhaust from the Q-SUN out of the lab. AMNH/F. Ritchie

Setting Test Parameters

Our next unexpected hurdle was in setting our testing parameters inside the Q-SUN (i.e. the RH, chamber air temperature, and irradiance). Our previous dye testing was undertaken following the ASTM D4303 (Method C) testing standard in a chamber that did not have the capacity to control for RH. Because our Q-SUN Xe-3 chamber can be run with RH control, we initially chose a different standard ASTM D4303 (Method D). Immediately, to our horror, we found that condensation was forming inside of the machine, dripping onto the carefully prepared samples and making them unusable.

Initial troubleshooting with Q-Lab Corporation (the Q-SUN manufacturer) focused on possible problems with sensors or calibration within the machine, but that did not solve the condensation problem. Ultimately we learned that the D4303 test Method D is outside the capabilities of the Q-SUN Xe-3 (and apparently outside the capabilities of any humidity controlled xenon arc testing chamber). This was not an intuitive conclusion since Method D is specifically written for a Humidity Controlled Xenon Arc Device. As such, we have adjusted our test parameters so that they now lie well within the capabilities of the machine, and more closely replicate the Museum’s diorama conditions that we are chiefly concerned with.

Lesson: Understand that standards are often simply guidelines to follow to provide consistent parameters for comparison. Standards can (and often, should) be adapted to meet necessary requirements.

Dealing with Malfunctions

The most recent wrinkle in our operation of this machine was the spontaneous cracking of one of the UV-blocking filters that we are using for half of the testing rounds. Though this required us to suspend our testing for a few days, Q-Lab Corporation was very quick in providing a replacement, and since then we have been able to run the unit without incident.

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Crack in a portion of the glass UV filter. AMNH/F. Ritchie

Lesson: Be flexible and ready to deal with unforeseen circumstances, and maintain a good relationship with the manufacturer of your equipment.

Budgeting for Consumables

The Q-SUN Xe-3 requires air filters, water purification filters, replacement lamps, sample preparation supplies, and many other expendable items that add cost beyond the initial purchase of the machine. Our grant budget has been adequate to deal with consumable materials, but we have realized that we must be prudent when running the machine and we must stay on top of ordering replacement supplies. There are even differences between test cycles. We are finding that our UV-filtered test cycles use up the lamps and water filters more quickly than the UV-rich test cycles.

Lesson: Pad your budget for expendable supplies and be sure to order the next set of replacements as soon as you install the first set.

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Row of Q-SUN replacement lamps awaiting installation. AMNH/F. Ritchie

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Project Conservator replacing a lamp. AMNH/J. Sybalsky

CONCLUSION

Owning and operating an accelerated aging chamber, at least one as complex as the Q-SUN Xe-3, is more than a plug-and-play operation. We hope that the steepest part of the learning curve is now behind us, but past experiences have taught us to expect that new issues will present themselves as we continue to work with this machine.

Lesson: When using any new tool or taking on any new experimental analysis, be sure to build time into the project timeline for troubleshooting.