Ellen Pearlstein

Evaluating Color and Fading of Red-Shafted Flicker (Colaptes auratus cafer) Feathers: Technical and Cultural Considerations

Abstract Fading behavior of undyed feathers has not received much attention in conservation literature and as a result feathers are categorized with other natural materials as being fugitive to display lighting, based on anecdotal evidence. The authors investigated Red-shafted Flicker feathers, which have carotenoid-based colorant systems and significance in North American native regalia, to demonstrate how lighting guidelines could be informed by a multivariate approach that considers material sensitivity, properties of value, and use before entering a museum collection. Ornithological literature reviewed demonstrates that feathers are highly differentiated in their sources of coloration, which include chemistry, structure, diet, age and gender, all resulting in varying responses to illumination. The authors explore the value placed on color by original fabricators, and how use and attitudes toward color contribute to the collections for which we assume stewardship. Red-shafted Flicker feathers were exposed to equivalent photometric doses in order to compare results from window-fading and microfading to Blue Wool Standards. Results indicate color changes more stable than Blue Wool 1 and 2, with ultraviolet radiation playing a significant role in fading. Microfading is beneficial for measuring color change because the variability within and between feathers is eliminated as the sample site remains unvaried.

A REVIEW OF COLOR-PRODUCING MECHANISMS IN FEATHERS AND THEIR INFLUENCE ON PREVENTIVE CONSERVATION STRATEGIES

Abstract Lighting policies as part of a preventive strategy for feather collections in museums often do not consider the different colorant systems found in the feathers. Ornithological research about plumage coloration, while targeting an understanding of signaling in bird behavior, provides valuable information about different colorant systems and their response to light exposure. Because photosensitivity varies for different colorants, it is important for conservators to be able to identify colorants as a first step in designing a preventive strategy for feathers. Visual assessment methods are described as a means for helping conservators distinguish colorant mechanisms. Color measurement methods, especially as used to monitor color change, must be able to reproducibly measure feather colors despite their complex geometries. Measurement methods are referenced that permit reproducibility by accounting for the variations in measurement angles and feather position. Studies reviewed indicate that pigment-based color and structural color do not have the same light sensitivity, with pigment color being more sensitive. This light sensitivity will depend on the nature, concentration, and chemical environment of the pigment. Recent work provides evidence that the insensitivity of structural colors has been over-simplified and photochemical effects beyond fading are necessary and important directions for further study.

Restoring provenance to a Native American feather blanket

Abstract A technical examination of an unprovenanced feather blanket in the Agua Caliente Cultural Museum in California found turkey feathers, yucca fiber cordage, human hair, associated botanicals, and a documented twining technique indicating that the blanket likely derives from the prehistoric Southwest, possibly Basketmaker III–Pueblo I (ca. 700–950 AD), rather than from eighteenth to nineteenth century California as originally believed. Sources on excavated Southwest prehistoric fur and feather blankets, revival practices by contemporary Pueblo weavers, and physical examination of two historic California feather blankets indicate similarities and differences in materials and construction methods, and vastly different contemporary attitudes toward feather blankets in museums. This case study is an example of how conservation methods can be used in support of post-Colonial museum goals, benefiting traditional owners and indigenous communities. Reattribution from historic California to a Pueblo child burial in northern Arizona changes not only conservation treatment and display, but also the disposition of this object in the museums collection.

The occurrence of a titanium dioxide/silica white pigment on wooden Andean qeros: a cultural and chronological marker

A white pigment found on a sub-set of polychromed wooden Andean ritual drinking cups called qeros has been characterized by X-ray diffraction, X-ray fluorescence spectroscopy and Raman spectroscopy as consisting principally of cristobalite (SiO2), anatase (TiO2), and α-quartz (SiO2). This unexpected assemblage of minerals is like that reportedly found in an exposed titanium ore body in southern Peru, an area once part of the Inka Empire. The ore is a close match in color and composition to the white pigment found on the qeros and offers a possible candidate for the geological source of this material. The temporal horizon for the use of this pigment appears to be ca. 1532–1570, correlating with what we refer to here as the Transitional Inka/Early Colonial period, although production of polychromed qeros may have begun before this time and certainly continued well into the eighteenth century or later. Not long after the arrival of the Spanish, this titanium dioxide/silica pigment was replaced by lead white, a result of Spanish influence. We suggest that white pigments on qeros offer material evidence for establishing a chronology for these ritual vessels and that the titanium dioxide/silica pigment on this group of qeros constitutes a previously unidentified, naturally occurring white pigment indigenous to the southern Andes, the first use of which probably dates to the Pre-Columbian period.

AN EXAMINATION OF PLANT ELEMENTS USED FOR CAHUILLA BASKETS FROM SOUTHERN CALIFORNIA

Abstract Plant materials used in the production of traditional Cahuilla baskets from the historic period in San Diego and Riverside Counties in southern California were examined in order to relate their processing and morphology to their behavior in completed baskets. Details on the harvesting, processing, and weaving techniques for these plant materials, obtained from a traditional Cahuilla weaver and teacher, are included. The plants selected for examination are chaparral yucca (Hesperoyucca whipplei Torr.), deergrass (Muhlenbergia rigens (Benth) Hitchc.), juncus (Juncus textilis Buchenau), sumac (Rhus trilobata Nutt.), and palm (Washingtonia filiferia (Linden ex André) H. Wendl.). Physical descriptions of the processed fibers are provided, along with photomicrographs of surface and cross sections. Five Cahuilla baskets from the collections of the Agua Caliente Cultural Museum were selected for a detailed study of their construction techniques, including direct comparison of their construction materials to the reference fiber set. Results of nondestructive x-radiography of the baskets provided additional information about materials and coiling.

Conserving ourselves: Embedding significance into conservation decision-making in graduate education

Graduate conservation students are well educated in many aspects of their work; however, it is difficult in the classroom to teach students how to base their conservation decisions on aspects of cultural significance. It is widely acknowledged that conservation decisions are not neutral, that they depend on cultural context and upon the predilections of the conservator and the owning individual or institution. Partnerships between community members and conservators have had a long history within conservation practices described as ‘ethnographic’, and such methods have arguably influenced working practices within other conservation specialties. A graduate conservation class is described in which students conserved important heritage items belonging to their classmates, in an environment where access to discoveries of significance were encouraged for their ability to inform preservation decisions. Cases are described that link decisions with specific values.

Teaching Sustainable Collection Care

Teaching sustainable collections maintenance to graduate students in conservation as well as students in museum, library, and archives preservation is challenging. Students enter school with an exposure to preventive care, but are surprisingly unfamiliar with prescriptive ideas about requirements for temperature and relative humidity for collections, and therefore do not need to unlearn former rigid climate standards enforced in many institutions. Central to graduate conservation education is an understanding of the environmental responses of individual materials, and the contributions of climate mitigation to preservation. While there are some case studies, such as those reviewed in this paper, in which museums and libraries have achieved energy savings while maintaining collections preservation, further studies illustrating building and collection performance and energy savings, taken together, would aid both graduate instruction and preventive practice. For the first time in a class on sustainable collections maintenance at UCLA, graduate students monitored both the climate and the energy expenditures in a Leadership in Energy and Environmental Design (LEED) certified building housing a library collection. Both the architect and the engineer who shepherded the LEED process participated in course instruction. The students used an energy modeling calculator to measure the energy currently used to maintain indoor conditions, and compared this with energy needed to maintain stringent standards of 20°C and 45% RH year round. Calculating building energy data alongside environmental data teaches students about the complexity of crafting sustainable recommendations. It further pinpoints the importance of long-term collaborative work in the creation of sustainable preservation climates.

ULTRAVIOLET-INDUCED VISIBLE FLUORESCENCE AND CHEMICAL ANALYSIS AS TOOLS FOR EXAMINING FEATHERWORK

Abstract Feathers are found in cultural heritage collections of tribal arts from the Americas, Africa, and the Pacific as well as in contemporary art, European and American fashion, and in taxidermy and ornithology specimens. Although museum conservators routinely evaluate feathers by looking at insect damage and mechanical wear, as well as fading as evidence of light exposure, examination of feathers for visible fluorescence under an ultraviolet source is atypical. Recent research by both the authors and bird biologists indicate that ultraviolet fluorescence examination can provide valuable information about the identification and pigmentation of feathers found in museum collections. A number of feather pigments, including psittacofulvins found only in red and yellow pigments in birds in the Psittaciforme family, as well as porphyrins found in rusty brown owl plumage, may be identified by their specific ultraviolet-induced visible fluorescence. Feathers whose pigments are not directly fluorescent may still undergo appearance changes under an ultraviolet source as a consequence of light aging. Fluorescence is demonstrated to be an early marker of chemical change, and can be used to detect such change before it can be measured colorimetrically. The authors evaluate different methods of analysis, including ultraviolet-induced visible fluorescence, reflectance spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, gas chromatography/mass spectroscopy, and rates of pigment extraction for detecting light-induced physical and chemical changes in feathers. Results indicate that ultraviolet-induced visible fluorescence may be the most sensitive indicator of light-induced degradation. Museum featherwork, some with records of estimated display, was found to display ultraviolet-induced visible fluorescence changes analogous to photoaged feather samples.

Label removal from deteriorated leather-bound books

Abstract This research on label removal from leather was inspired by a real-life circumstance in a library where similar pressure-sensitive labels had been applied to the covers of a series of eighteenth-century leather-bound books. The challenge was to develop a protocol for safely removing the unwanted labels that could be carried out by non-specialists outside of a laboratory without causing damage to the historic bindings. The adhesive was analysed with Fourier transform infrared spectroscopy and solubility tests. The degraded sheepskin was characterized by its follicle pattern, shrinkage temperature, spot tests and surface pH. A selection of mechanical and solvent-based techniques was evaluated, including removal with a scalpel, solvent gels, solvent poultices, solvent chambers and changes in temperature. The best results occurred when the paper label was thinned, followed by a cellulose fibre poultice with ethyl acetate applied to the thinned backing.

Featherwork: Beyond decorative

Abstract Investigation of the light sensitivity of feathers used in Californian material culture revealed that the cultural values held by these materials was crucial for their interpretation. It was evident that feathers are valued both for their tangible and intangible attributes and that tangible qualities, including color and shape, and modification and attachment methods, often have meaning beyond their decorative and practical functions. Several different feather-working cultures, the birds that are important to these communities, how feathers from these birds are used to make featherwork, and how objects reveal changes in tradition over time are examined. Much of this information requires reference to a combination of sources, including historical and contemporary accounts, discussions with native featherworkers, ethnologists and ornithologists, and close examination of feathered objects in museum collections. This multidisciplinary approach leads to a more thorough understanding of feathered objects and aids conservators in better interpreting whether modifications are the result of access to feathers, intentional alterations of cultural use, or museum display.