Christopher A. Maines

Condition Problems Related to Zinc Oxide Underlayers: Examination of Selected Abstract Expressionist Paintings from the Collection of the Hirshhorn Museum and Sculpture Garden, Smithsonian Institution

Abstract The presence of zinc oxide oil paint and the condition problems observed in a group of paintings from the collection of the hirshhorn Museum and sculpture garden prompted analytical examination of the museums mid-20th century holdings. results reveal a link between upper layer deterioration and underlying zinc oxide paint layers, and suggest that certain visible signs of deterioration may signal the presence of more serious and widespread condition problems. the popularity of zinc oxide house paint among mid-century artists creates a higher probability of this type of deterioration in works from this period.

Modification of Surface Roughness by Various Varnishes and Effect on Light Reflection

Abstract The modification of microscopically rough surfaces by commonly used varnishes and resultant changes in light reflection from these surfaces were studied using laser scanning confocal microscopy, stylus profilometry and specular gloss and distinctness-of-image gloss measurements. Natural resins as well as synthetic low molecular weight and polymeric resins were studied. The molecular weights of the resins were determined using size-exclusion chromatography. All the low molecular weight resins, with weight-average molecular weights in the range 800–6500, including the natural resins, essentially produced smooth surfaces and eliminated high-frequency as well as low-frequency roughness, while polymeric resins, with weight-average molecular weights between about 25000 and 210000, produced rougher surfaces, eliminating high-frequency roughness but not all low-frequency roughness. The spatial frequency range of the roughness of the polymeric coatings decreased with increasing molecular weight. As a result, low molecular weight varnishes reduced small-angle scattering about the specular reflection to a greater extent than the polymeric coatings. Polymeric varnishes, therefore, demonstrated lower specular gloss and, in particular, lower distinctness-of-image gloss. Distinctness-of-image gloss values showed good correlation with the weight-average molecular weights of the resins. The power spectral density of the surfaces coated with low molecular weight resins showed a sharper falloff at low spatial frequencies than the polymeric resins.

“TRANSPARENCY AND LIGHT, STRUCTURE AND SUBSTANCE”: ENAMEL PAINTS IN LáSZLó MOHOLY-NAGY'S Z VII (1926)

Abstract Z VII (1926), a painting by Hungarian-born artist László Moholy-Nagy in the collection of the National Gallery of Art, Washington, D.C., is striking for its richly varied surface, a quality unusual for his paintings from the period. Recent conservation treatment exposed a range of carefully calibrated and deliberate juxtapositions of smooth glossy and subtly textured matte paints on its surface. Subsequent scientific analysis conducted at the Gallery indicates that enamel paints were used discretely in several areas of the painting. This study addresses the use of these new materials in the artists repainting of Z VII.

Unraveling the modified surface of the photographic paper “Japine”

Modification of the surface of a paper intended for coating with a photographic sensitizer will influence both its chemical and physical characteristics. A scientific examination was performed on the photographic paper, Japine, produced by the Platinotype Company from 1906 to 1937 for their platinum, silver, and palladium printing processes. Scanning electron microscopy (SEM) and non-invasive imaging by optical coherence tomography (OCT) reveal the presence of a very thin layer at the paper surface. Detailed investigation by attenuated total internal reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and gas chromatography-mass spectrometry (GCMS) analyses determined that this surface consists of a parchmentized layer created by chemical modification of the paper support rather than the presence of an applied coating. Reverse engineering studies suggest that the paper was prepared by treatment with sulfuric acid under select conditions to modify the structure of the cellulose only at the paper surface. SEM imaging demonstrates that the distribution of the platinum particles that make up the image is significantly altered on surface parchmentized papers compared to unmodified papers.

AN INVESTIGATION INTO JAPINE PLATINUM PHOTOGRAPHS: WILLIAM WILLIS'S PROPRIETARY PAPER

Abstract Analyses of two samples of the commercial platinum photographic paper “Japine” revealed that this trade-name product was sold with a range of surface properties from matte to glossy. An in-depth examination of an unprocessed glossy Japine sample showed a chemically modified surface resulting from parchmentization by treatment with sulfuric acid. This treatment results in a thin film of amorphous cellulose on the printing surface, altering its visual appearance and wet strength. Photographers selected this paper due to its aesthetic qualities. However, such papers have never been characterized and are essentially unknown to modern-day scholars who may mistake them as prints with thin binder layers, such as albumen or gelatin. Indeed, the approach to conservation of these photographs may differ from one designed for a traditional platinum print. The parchmentized Japine paper was criticized for its tendency to crack, one characteristic that may have implications for its handling and conservation treatment today.