Papers by Samantha Alderson
Heritage Science, Apr 9, 2021
The collection of the American Museum of Natural History, New York, includes a set of four elabor... more The collection of the American Museum of Natural History, New York, includes a set of four elaborately painted 19th-century Tsimshian house posts that have been on continuous open display for more than a century. Over time, these objects have accumulated surface grime, and several coating layers applied in undocumented past restoration campaigns, some of which have yellowed with age. The combination of heavy soiling and multiple coatings has obscured the underlying polychromy, shifting the colors of the wood and paints, and yielding improper surface appearances. Further, some of the coatings appeared to have sunk into the media-lean paints, complicating removal. Questions regarding the number, types, and timing of coating applications, as well as the nature of some of the paint below, set the stage for an in-depth technical study aiming to inform the conservation treatment of these poles being undertaken in connection with the renovation of the Northwest Coast Hall at the museum. Microscopic examination of numerous cross sections removed from the four house posts under polarized and ultraviolet (UV) illumination shed light on the number of coating layers present in selected areas and their location in relation to the overall stratigraphy. Micro-invasive analysis of samples relied on a combination of spectroscopic and chromatographic techniques, including transmission Fourier-transform infrared (FTIR) spectroscopy, attenuated total reflection (ATR)-FTIR spectroscopy, and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), aiming to determine the exact chemical composition of the coatings. Portable X-ray fluorescence (XRF), FTIR, Raman, and scanning electron microscopy with energydispersive X-ray spectroscopies (SEM/EDS) provided insight into the color palette used, with a focus on green paints. Investigation of the coatings revealed the application of multiple layers, including cellulose nitrate and localized areas of polyvinyl acetal. Analysis of the paint identified a limited range of inorganic pigments and, additionally, assisted in tackling issues that arose during the cleaning of specific colored areas. Results from this technical study helped address outstanding questions regarding this group of historical Tsimshian house posts, informing the development of a suitable treatment tailored to the safe removal or reduction of surface coatings and grime, ultimately improving the legibility of the design and colors.
Journal of Cultural Heritage
While undertaking treatment of a monumental Northwest Coast wooden carving at the American Museum... more While undertaking treatment of a monumental Northwest Coast wooden carving at the American Museum of Natural History, conservators encountered a difficult cleaning challenge. The 19th century painted red cedar carving served as a house entry pole in the Nuxalk village of Bella Coola in the province of British Columbia, Canada. The painted surface was weathered by years out of doors in front of the house of Chief Pootlass and obscured by darkened museum-applied coatings and grime acquired during more than 100 years of open display at the museum. The methods used to reduce the grime and cellulose nitrate coating found on the surface overall were not successful when applied to the green painted areas on the bottom of the pole, as it was covered with an additional coating of poly(vinyl acetal) resin. The present work reports on the testing and use of aqueous nanostructured fluids (NSFs) and hydrogels for succesfully cleaning these areas, where other methods could not be used safely. There have only been a few published examples of these recently developed cleaning fluids and gels being used on art objects and this is the first known use on this type of material. Further analyses were performed following the cleaning. Micro-reflectance FTIR, optical microscopy, SEM-EDX, and NMR were used to characterize paint and coating samples taken from the carving. In addition, laboratory tests were performed to evaluate the response of poly(vinyl acetal) to a selection of NSFs, providing an understanding of the mechanisms underlying the successful cleaning performed on the pole by the conservators.
Additional file 2: Fig. S2. Polarized light microphotograph of cross section S5 from house post 1... more Additional file 2: Fig. S2. Polarized light microphotograph of cross section S5 from house post 16/567, i.e. light green paint from the leg of a frog, clearly showing that the paint migrated into the upper cells of the wood.
Additional file 9: Fig. S9. Transmission FTIR spectra of sample S5 from house post 16/568, i.e. &... more Additional file 9: Fig. S9. Transmission FTIR spectra of sample S5 from house post 16/568, i.e. "disturbed" area of red paint over filled crack from a woodpecker at the top of the pole. Bands at 3365, 2933, 1652, 1153, 1079, and 1022 cm− 1 are attributed to starch.
Additional file 5: Fig. S5. Proper left side of the frog figure on 16/567 after treatment, showin... more Additional file 5: Fig. S5. Proper left side of the frog figure on 16/567 after treatment, showing two shades of green paint.
Additional file 4: Fig. S4. Raman spectra of a sample S6 from house post 16/568, i.e. "intac... more Additional file 4: Fig. S4. Raman spectra of a sample S6 from house post 16/568, i.e. "intact" area of black paint from the bear's eyebrow, and b sample S4 from house post 16/568, i.e. "intact" area of red paint from a woodpecker at the top of the pole. In spectrum a, bands at ≈ 1335 and ≈ 1575 cm− 1 are assigned to a carbon-based black. In spectrum b, bands at 252, 284, and 343 cm− 1 are attributed to vermilion.
Additional file 6: Fig. S6. a Polarized and b UV light microphotographs, as well as c BSE image o... more Additional file 6: Fig. S6. a Polarized and b UV light microphotographs, as well as c BSE image of cross section S4 from house post 16/567, i.e. dark green paint from the leg of a frog, unequivocally displaying only one layer of paint.
Additional file 8: Fig. S8. A detail of cupping and flaking red paint over fill material, from th... more Additional file 8: Fig. S8. A detail of cupping and flaking red paint over fill material, from the top woodpecker figure of house post 16/568.
Additional file 7: Fig. S7. UV light microphotograph of cross section S3 from house post 16/565, ... more Additional file 7: Fig. S7. UV light microphotograph of cross section S3 from house post 16/565, displaying diffusion of soiling into the paint layer.
Additional file 1: Fig. S1. Location of samples removed from the AMNH Tsimshian house posts in th... more Additional file 1: Fig. S1. Location of samples removed from the AMNH Tsimshian house posts in this study. Line drawings by Kayla D. Younkin, 2018.
Additional file 3: Fig. S3. Polarized light microphotograph of cross section S2 from house post 1... more Additional file 3: Fig. S3. Polarized light microphotograph of cross section S2 from house post 16/565, i.e. coating over gray paint from a seal at the bottom of the pole, and b UV light microphotograph of cross section S8 from house post 16/568, i.e. green paint from the eye of a standing wolf or bear, showing a brown-yellow layer of presumed drying oil just underneath the samples' surface.
The ceramic vessels known as Zapotec or Oaxacan urns are among the most recognizable and signific... more The ceramic vessels known as Zapotec or Oaxacan urns are among the most recognizable and significant products of the Zapotec culture, which flourished in the Valley of Oaxaca Mexico from A.D. 200 - 800. There are hundreds of these objects in museum collections throughout the world and they have been published widely, however, beyond authentification studies, scant technological information about these important artifacts has appeared in the literature. The American Museum of Natural History holds one of the largest collections of urns outside of Mexico, including many excavated in 1898 at Xoxocotlán. This material offered a unique opportunity to undertake a technological study of an important collection of well-provenanced urns together with other artifacts from the same excavations. The study focused primarily on the painted surfaces of the urns. It appears that almost all Zapotec urns were at least partially painted, however, this aspect of the urns has not previously received a great deal of attention. For the study, the surfaces of the urns were carefully examined and diagramed using a binocular microscope. Paint samples were taken from the urns and other related material for analysis. The pigments were identified using microchemical tests, polarized light microscopy (PLM), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). A few larger samples were taken for examination of the paint layers in cross-section. The study revealed designs and patterns painted on these urns that are not readily apparent and could be easily overlooked without careful examination. The study also showed evidence of repainting and reuse of the urns. The analysis resulted in the positive identification of the important pigment Mayan Blue on Zapotec artifacts and an interesting pattern in the use of red pigments (cinnabar and iron oxides) on the artifacts sampled.
Journal of the American Institute for Conservation
ABSTRACT Several poly(vinyl acetate) resins that continue to be important and useful in many area... more ABSTRACT Several poly(vinyl acetate) resins that continue to be important and useful in many areas of conservation are no longer available, namely, the AY series manufactured by the Union Carbide Corporation (AYAC, AYAA, AYAF, AYAT), and Mowilith 20 originally manufactured by the Hoechst Corporation. To identify potential substitutes, comparable resins were obtained from manufacturers and their properties were investigated and compared to the discontinued resins. Non-instrumental analysis was conducted to assess basic properties and measure relative viscosity. In addition, instrumental analysis was used to measure molecular weight, glass transition temperature, and chemical composition. The collected data were compiled and evaluated to determine potential substitutes for each of the discontinued resins.
Journal of Cultural Heritage, 2022
While undertaking treatment of a monumental Northwest Coast wooden carving at the American Museum... more While undertaking treatment of a monumental Northwest Coast wooden carving at the American Museum of Natural History, conservators encountered a difficult cleaning challenge. The 19th century painted red cedar carving served as a house entry pole in the Nuxalk village of Bella Coola in the province of British Columbia, Canada. The painted surface was weathered by years out of doors in front of the house of Chief Pootlass and obscured by darkened museum-applied coatings and grime acquired during more than 100 years of open display at the museum. The methods used to reduce the grime and cellulose nitrate coating found on the surface overall were not successful when applied to the green painted areas on the bottom of the pole, as it was covered with an additional coating of poly(vinyl acetal) resin. The present work reports on the testing and use of aqueous nanostructured fluids (NSFs) and hydrogels for succesfully cleaning these areas, where other methods could not be used safely. There have only been a few published examples of these recently developed cleaning fluids and gels being used on art objects and this is the first known use on this type of material. Further analyses were performed following the cleaning. Micro-reflectance FTIR, optical microscopy, SEM-EDX, and NMR were used to characterize paint and coating samples taken from the carving. In addition, laboratory tests were performed to evaluate the response of poly(vinyl acetal) to a selection of NSFs, providing an understanding of the mechanisms underlying the successful cleaning performed on the pole by the conservators.
Heritage Science, 2021
The collection of the American Museum of Natural History, New York, includes a set of four elabor... more The collection of the American Museum of Natural History, New York, includes a set of four elaborately painted 19th-century Tsimshian house posts that have been on continuous open display for more than a century. Over time, these objects have accumulated surface grime, and several coating layers applied in undocumented past restoration campaigns, some of which have yellowed with age. The combination of heavy soiling and multiple coatings has obscured the underlying polychromy, shifting the colors of the wood and paints, and yielding improper surface appearances. Further, some of the coatings appeared to have sunk into the media-lean paints, complicating removal. Questions regarding the number, types, and timing of coating applications, as well as the nature of some of the paint below, set the stage for an in-depth technical study aiming to inform the conservation treatment of these poles being undertaken in connection with the renovation of the Northwest Coast Hall at the museum. Mi...
Fossil preparators have a range of adhesives to choose from and it is often difficult to select o... more Fossil preparators have a range of adhesives to choose from and it is often difficult to select one most suitable for any given task. The adhesives that preparators use can be divided into two basic categories: solution adhesives, which include Paraloid B-72, Butvar B-76, Butvar B-98, and McGean B-15; and reaction adhesives, which include various brands of epoxies and cyanoacrylates. Both types of adhesives share some basic characteristics, however, solution and reaction adhesives differ fundamentally in the manner in which they set or solidify. Understanding the distinction between these two types of adhesives helps to explain differences in both their working and final properties. This information can assist the preparator in making an appropriate and successful adhesive selection when joining, consolidating or coating a specimen. Davidson, A. and S. Alderson. 2009. An introduction to solution and reaction adhesives for fossil preparation. In: Methods In Fossil Preparation: Procee...
Fossil preparators have a range of adhesives to choose from and it is often difficult to select o... more Fossil preparators have a range of adhesives to choose from and it is often difficult to select one most suitable for any given task. The adhesives that preparators use can be divided into two basic categories: solution adhesives, which include Paraloid B-72, Butvar B-76, Butvar B-98, and McGean B-15; and reaction adhesives, which include various brands of epoxies and cyanoacrylates. Both types of adhesives share some basic characteristics, however, solution and reaction adhesives differ fundamentally in the manner in which they set or solidify. Understanding the distinction between these two types of adhesives helps to explain differences in both their working and final properties. This information can assist the preparator in making an appropriate and successful adhesive selection when joining, consolidating or coating a specimen.
Fossil preparators have a range of adhesives to choose from and it is often difficult to select o... more Fossil preparators have a range of adhesives to choose from and it is often difficult to select one most suitable for any given task. The adhesives that preparators use can be divided into two basic categories: solution adhesives, which include Paraloid B-72, Butvar B-76, Butvar B-98, and McGean B-15; and reaction adhesives, which include various brands of epoxies and cyanoacrylates. Both types of adhesives share some basic characteristics, however, solution and reaction adhesives differ fundamentally in the manner in which they set or solidify. Understanding the distinction between these two types of adhesives helps to explain differences in both their working and final properties. This information can assist the preparator in making an appropriate and successful adhesive selection when joining, consolidating or coating a specimen.
Journal of the American Institute for Conservation , 2019
Several poly(vinyl acetate) resins that continue to be important and useful in many areas of cons... more Several poly(vinyl acetate) resins that continue to be important and useful in many areas of conservation are no longer available, namely, the AY series manufactured by the Union Carbide Corporation (AYAC, AYAA, AYAF, AYAT), and Mowilith 20 originally manufactured by the Hoechst Corporation. To identify potential substitutes, comparable resins were obtained from manufacturers and their properties were investigated and compared to the discontinued resins. Non-instrumental analysis was conducted to assess basic properties and measure relative viscosity. In addition, instrumental analysis was used to measure molecular weight, glass transition temperature, and chemical composition. The collected data were compiled and evaluated to determine potential substitutes for each of the discontinued resins.
The field of art conservation has used Polyvinyl acetate PVAC for consolidation and retouching si... more The field of art conservation has used Polyvinyl acetate PVAC for consolidation and retouching since the 1930s. Its use as a retouching medium was first mentioned in a 1935 journal, Technical Studies in the Field of the Fine Arts, published from 1932-42 by the Fogg Art Museum. PVAC paints were found to exhibit little or no discoloration upon aging, could be dissolved in a range of solvents including alcohols, glycol ethers, acetone, and toluene, and could maintain both clarity and reversibility. Hoescht Mowilith 20 and Union Carbide AYAB were the typical PVAC resins used for inpainting. Collaboration between Golden Artists Colors and painting conservators led to the introduction of Golden’s pre-made PVAC conservation paints based on a blend of Union Carbide AYAA and AYAC in 1991. Mark Golden also created custom-made retouching paints for the 1988-1992 treatment of Whistler’s Peacock Room in the Freer Gallery of Art. Unfortunately, both the Mowilith and Union Carbide resins were discontinued causing Golden to cease production of the line in 2010. Continued interest in PVAC retouching paints inspired Golden to collaborate with conservators and conservation scientists to reformulate a new conservation paint line three years later. After much testing, the company was once again able to provide conservators with pre-made PVAC conservation paints in 2017. This talk will briefly outline the history of PVAC retouching paints and discuss some of the specific properties of the new Golden line including molecular weight, gloss, solubility, and practical application tips with examples from the authors’ personal conservation treatments.
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Papers by Samantha Alderson