Dawn Rogala’s research while affiliated with Conservation Biology Institute and other places

On June 6, 1949, members of the Victorian Branch of the Oil and Colour Chemists’ Association gathered in Melbourne, Australia, to share their concerns regarding a sudden increase in problems associated with zinc oxide oil paints, problems which Association members posited were tied to industry-wide changes in processing methods for the zinc oxide pigment. The issues raised during this meeting inform and parallel current studies regarding metal soap behavior. This paper reviews the topics discussed at the 1949 symposium, distilling the historical research and its relationship to modern conservation and scientific inquiry. Topics include existing research literature, pigment processing methods and observed relationships between particle morphology and paint film behavior, and zinc oxide paint film failure patterns. Related metal soap research from the period is also discussed, including investigations of zinc oxide soap formation, the effect of environment on soap formation and film failure in zinc oxide oil paints, and the impact of zinc oxide-specific failure mechanisms on single- and composite-paint systems.

This paper summarises the analysis of more than 500 paint and fibre samples from the late-career work of Abstract Expressionist painter and teacher Hans Hofmann (1880–1966) and finds a correlation between condition issues in Hofmann’s work and the combination of new paint materials with traditional art practice. The results of this study help to inform the conservation of Abstract Expressionist and other works that incorporate both traditional and modern paint media.

A recent visual survey of Abstract Expressionist-era paintings in the collection of the Hirshhorn Museum and Sculpture Garden (HMSG), Smithsonian Institution revealed a particular type of paint layer separation. Earlier work by the authors showed that zinc oxide in oil paint is a contributing factor to the problem. Ten samples from five Abstract Expressionist-era paintings as well as twenty-three samples eight years or older from the Smithsonian Institution’s (SI) Materials Study Collection were analyzed by pyrolysis – gas chromatography – mass spectrometry (Py-GC-MS), and unexpectedly significant amounts of oleic (cis-octadecenoic) acid were detected in samples containing high proportions of zinc oxide (25 % or greater by weight). In a typical fully cured oil paint, the oleic acid is oxidized to azelaic (nonanedioic) acid. Although the formation of zinc soaps in oil paints is well-known, the detection of zinc oleate in paints by Py-GC-MS has never been described. The close-packing of the oleate chains in the plate-like structure of zinc oleate prevents the oxidation of the cis-double bond, and therefore prevents the formation of azelaic acid. The detection of zinc oleate in paintings is an indication that the paint layers are at risk for future separation.

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 museum's 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.