Research: Care and Conservation


From 2013–2022, the Science Conservation lab staff conducted research on the conservation of historic mammal and bird taxidermy mounts through two National Leadership Grants awarded by the Institute for Museum and Library Services (IMLS): IMLS National Leadership grant MG-30-13-0066-13, Recoloring Faded Taxidermy, 10/1/2013–9/30/2017 (Recoloring Faded Fur), and IMLS National Leadership Research Grant, MG-60-18-0031-18, Continuing Conservation Research Challenges: The Impact of Cleaning and the Preservation and Restoration of Color on Historic Taxidermy, 9/1/2018–8/31/2022 (Conservation of Feathers). We are very grateful for the IMLS and their continued support of our work.

Research Questions 

  • What condition issues are most prevalent in taxidermy mounts?  
  • How are other professionals caring for and treating historic taxidermy?  
  • What materials and techniques are recommended for cleaning fur and feather objects?
  • Which materials and methods may be considered to restore color to faded feathers and fur?
  • Does the use of pesticides on or in proximity to collections impact keratin preservation?

A project blog, In their True Colors, follows these research efforts over the duration of both grant periods, and beyond.

Recoloring Faded Fur

The overarching goal of the initial research project, Recoloring Faded Fur, was to develop best practices for recoloring faded mammal taxidermy. While the direct physical application of colorants on top of degraded substrates would not be appropriate for many collections, this approach is a convention in the restoration of taxidermy, reflecting the importance that is placed on the naturalistic appearance of the animal. 

Research included devising methods that would minimally alter the texture or sheen of fur, and remain as reversible or re-treatable as possible. An AMNH pilot study determined that metal-complex solvent dyes commonly known as Orasol dyes (BASF) are well suited for this challenge: the earthy palette colors mirrors the tones in mammal pelage, and dyes can be airbrushed onto fur in low-toxicity solvents without a binder, which avoids the risks that aqueous systems pose to degraded skin. When used in this way, dyes deposit onto the fiber surface and can be removed with additional solvent for future retreatment if needed.

Orasol dyes were developed in industry to color printing inks, plastics and solvent products, comprising predominantly 1:2 chrome, 1:1 chrome, and 1:2 cobalt metal-complexes containing azo, monoazo, azomethine, and azo xanthene structures. They have a history of use in conservation to tint resin coatings and fills, as well as wood stains, but their use on keratin in the absence of a binder was untested. Investigations considered three related research questions:

Summary of Fur Recoloring Research Results: 

  • When used without a binder, lightfastness in metal complex dyes often differs from published values derived from resin films.
  • The product line exhibits a wide range in lightfastness.
  • Most colors have good to excellent light stability.
  • Stable dyes are available throughout the spectrum of colors.
  • Most colors perform as well on keratin fiber as they do on an inert substrate.
  • Even those of intermediate stability may provide acceptable longevity in some cases.
  • Orasol dyes are NOT associated with a significant increase in photo-oxidation of keratin over and above the natural rate. 
  • After aging, some dyes cannot be completely removed by washing in common solvents; Use blue dyes as minor constituents in dye mixtures to limit complications in retreatment.Durable recoloring treatments can be achieved using Orasol dyes. BW5 or even BW4-grade materials may have acceptable longevity in some recoloring applications if lighting is UV filtered.
  Color Index Name / New BASF Name / Old BASF Name Blue Wool Equivalent
  CI Red 118 / Orasol Red 471 / - 7
  CI Red 119 / Orasol Red 355 / - 2-3
  CI Red 122 / Orasol Red 335 / - 4-5
  CI Red 122 / Orasol Red 395 / Orasol Red BL 4-5
  CI Red 125 / Orasol Red 363 / Orasol Red G 4-5
  CI Red 127 / Orasol Pink 478 / Orasol Pink 5BLG 2-3*
  CI Red 130 / Orasol Red 330 / Orasol Red 3GL 3
  CI Red 160 / Orasol Red 365 / - 4-5
  CI Red 233 / Orasol Red 385 / Orasol Red 2B 5
  CI Orange 11 / Orasol Orange 247, Orasol Orange G 7
  CI Orange 54 / Orasol Orange 251 / - 4
  CI Orange 56 / Orasol Orange 245 / - 5-6
  CI Orange 99 / Orasol Orange 272 / Orasol Orange RG 4-5**
  CI Yellow 25 / - / Orasol Yellow 3R not tested
  CI Yellow 79 / Orasol Yellow 081 / - 4
  CI Yellow 81 / Orasol Yellow 141 / - 4
  CI Yellow 82 / Orasol Yellow 157 / - 4-5
  CI Yellow 88 / Orasol Yellow 152 / 2GLN 4-5
  CI Yellow 89 / Orasol Yellow 190 / 2RLN 7-8
  CI Yellow 146 / - / Orasol Yellow 2GN 2***
  CI Blue 67 / Orasol Blue 825 / Orasol Blue GN 6
  CI Blue 70 / Orasol Blue 855 / Orasol Blue GL 6
  CI Brown 42 / Orasol Brown 322 / Orasol Brown 2GL 6-7
  CI Brown 43 / Orasol Brown 324 / Orasol Brown 2RL 7-8****
  CI Brown 44 / Orasol Brown 326 / Orasol Brown 6RL 7-8
  CI Black 27 / Orasol Black X51 / - 7
  CI Black 28 / Orasol Black X45 / Orasol Black CN 6-7
  CI Black 29 / Orasol Black X55 / Orasol Black RLI 6-7

* Exception: all products BW1 with ethyl acetate
** Exception: all products BW6 with acetone
*** Exceptions: Orasol (BASF) branded dye supplied by Kremer Pigments, BW4 with ethyl acetate and propylene glycol monomethyl ether (PGME)
**** Exception: Sorasolve (FSW) branded dye supplied by Museum Service Corp., BW 5-6 with all solvents

More details on this research can be found in the article, An investigation into the lightfastness of metal-complex solvent dyes for use in the restoration of faded mammal taxidermy, which was presented at the ICOM Committee for Conservation 18th Triennial Meeting Copenhagen Denmark 4-8 September 2017.

Conservation of Feathers

The second IMLS-funded project, Continuing Conservation Research Challenges: The Impact of Cleaning and the Preservation and Restoration of Color on Historic Taxidermy, focused on a systematic evaluation of three distinct concerns in the conservation of feathers and feather objects. 

The research program was developed out of priorities articulated in an online community survey of nearly 100 allied preservation professionals, ensuring that it centered on concerns that reflect common needs. 

The survey data was supplemented with a series of artist interviews conducted by the research team in the fall of 2020. These recorded consultations were intended to explore the perspectives that indigenous artists and regalia makers, sculptors, and taxidermists bring to their decision-making about feather selection, cleaning and preparation, manipulation of structure and/or color, methods of storage, and pest prevention, providing additional perspectives on the meaning of transformations taking place during deterioration and treatment.

The research team also conducted an extensive review of published literature related to feather biology and conservation, assembling the Feather Conservation Library, a publicly available Zotero database of roughly 250 references that are curated, categorized, tagged, and available to all.

Impact of Cleaning Methods for Feathers

The cleaning study considered the unintended physical and chemical changes associated with cleaning, and progressed in three phases.​ 

Research reinforced the expectation that both wet and dry methods can cause moderate to severe damage to degraded feathers in the short term; but wet methods are, on the whole, more damaging than dry. All aqueous in particular methods carry significant risk for degraded keratin by causing barbules to deform and disengage​. Condition has a major impact on outcomes in cleaning and nearly all methods were associated with more damage in aged feathers than in fresh ones. In general, biopigments, particularly melanins, demonstrated some protective benefit. None of the methods tested were associated with detectable changes in color of keratin or carotenoid or melanin bio pigmentation, or with extreme changes in degradation behavior during accelerated aging. 

Restoring Lost Color to Feathers

Like many organic materials, keratin and biopigments in feathers are highly sensitive to light exposure. As a consequence, caretakers of these collections often have a responsibility to decide whether and how light-damaged objects should be displayed. If compensating for lost color is appropriate, best practice starts with a careful analysis of potential materials and techniques to be used, including the likelihood of damage to original materials, the lightfastness/durability of the treatment, and the possibility of future retreatment. This study aimed to identify effective, durable recoloring media for restoring faded feathers. 

  • Two approaches for restoring color to faded feathers were explored:
    • Direct recoloring of original feathers through the application of a colorant onto the faded feather
    • Construction of naturalistic fills from commercial poultry feathers, trimmed and toned with artist materials, then inserted among the original feathers over those that have faded, or in place of those that are lost
  • Potential colorants were evaluated in terms of whether they:
    • Provide acceptable lightfastness and the palette needed to replicate naturalistic color in faded and deteriorated feathers
    • Can be applied and removed without unwanted changes to feathers’ structure and arrangement
    • Can be used without inhibiting routine cleaning

This investigation also began with a preliminary investigation of methods described in the community survey, followed by in-depth studies of selected materials.  

These colorants tested included options that can work well for both approaches to restoration. As one might expect, some media are better suited to replicating specific patterns and colors than others. Selecting the best method requires attention to the coloration, condition, and morphology of the feather being restored, and how the object will be used in the future.

Impact of Pesticides on Feathers

Much of our current understanding of how pesticides impact feathers is anecdotal, so the goal of this study is to inform a more evidence-based approach to this aspect of pest management. The pesticide study aimed to address the long-term impacts of insecticidal materials that are in use today, excluding others used historically that are now largely abandoned due to the dangers they pose to humans and ecosystems.

Survey respondents and supplemental consultants identified roughly 25 commercially available insecticidal materials of interest to the preservation community. After researching their composition, availability, extent of use, and the feasibility of safely conducting lab-based testing, a smaller set of 13 materials was selected for study.

This real-time aging experiment will look at how sample feathers are affected when they are placed in tightly sealed jars with proportionally scaled doses of each pesticide. Each materials was mixed and/or applied in accordance with product label instructions or with reported practice; in some cases this meant placing the pesticide in the jar alongside the feather, while in other it meant a direct application. Over a period of at least ten years, the jars will be opened annually so that the feathers within can be imaged and analyzed using spectrophotometry and FTIR to detect changes in structure, color, and oxidation relative to a set of controls. Pesticides that require it will be reapplied before the jars are closed for another year, imitating a schedule of preventive pest treatments taking place in collection storage. Future analyses are scheduled to occur annually, and the research team hopes to make initial findings public in the next 3 to 4 years. 

Pesticide (chemical)​ Form​ Brand/scientific name​ Mode of Application
Naphthalene​ solid​ (flakes) Enoz Old Fashioned Moth Flakes​ Fumigation
Paradichlorobenzene​ solid ​(chunks) Enoz Ice Crystals​ Fumigation
Paradichlorobenzene​ Solid (urinal cake with cherry-scented additive​) ULINE Para Toilet Bowl Block​ Fumigation
Cypermethrin​ 0.1% liquid concentrate​ Constrain​ Applied to feathers
Beta-Cyfluthrin​ 10% solid concentrate (0.03% solution)​ Tempo Ultra WP​ Applied to jar interior
Pyriproxyfen​ 10% liquid concentrate (0.03% solution)​ NyGuard Insect Growth Regulator​ Applied to jar interior
Beta-Cyfluthrin/Pyriproxyfen​ mixture ​ Tempo Ultra WP/NyGuard IGR​ Applied to jar interior
Dichlorvos​ 20% solid concentrate​ Nuvan ProStrips​ Fumigation
Essential Oils (proprietary mixture)​ 6% liquid concentrate​ Mount Saver​ Applied to feathers
Borax ​ solid​ 20 Mule Team Natural Laundry Booster​ Applied to feathers
Amorphous silica  ​ solid​ CimeXa Insecticide Dust​ Applied to jar interior
Umbellularia californica leaves ​ California Bay Laurel​ (aka Pepperwood, Cinnamon Bush) Placed among feathers
Azadirachta indica leaves​ Neem ​(aka Nimtree, Indian Lilac) Placed among feathers