Protective Effects of Anoxic Enclosures
 

Previous studies (Arney, 1979) have suggested that while many light-sensitive pigments and dyes will benefit from being displayed in an oxygen-free environment, some will change via photo-reductive processes or show no effects whatsoever. These earlier studies selected a limited set of materials. Thus, as important as this work is, the full magnitude of the photo-reductive extent on colorants cannot be estimated. Some studies also used oxygen scavengers, which might not have attained low enough oxygen concentration to produce meaningful results. In these earlier studies, temperature and relative humidity were seldom controlled to the extent they would be in museum display conditions.

conservation image
 

Component Three, to be carried out at the GCI, applies nearly 15 years of Getty experience in designing and building environmentally-controlled, oxygen-free display cases, to photochemical damage research. For this research, a pair of matched display cases, one with a normal atmosphere and one with a nitrogen atmosphere, are irradiated under banks of MR-16 lamps. Temperature control is achieved with a re-circulating, liquid-cooled, closed loop system, which in turn allows for stable relative humidity conditions. The adjacent image shows Assistant Scientist Vincent Beltran standing next to the air and anoxia exposure set-ups during testing.

By the end of 2007, the first sample set had been exposed and their color changes measured. This set of samples consisted largely of pigments from the Forbes collection and the GCI Reference Collection, augmented by a set of experimental lake pigments provided by the Library of Congress and plant materials provided by Rob Waller at the Canadian Museum of Nature. The vast majority of samples during the initial exposure demonstrated a clear benefit from oxygen-free light exposure. The absence of oxygen, however, proved problematic for several samples.

Building upon the results of the first exposure, a second set of materials was exposed and assessed for color change during spring 2008. These included a large set of historic dyes on natural fiber made by Cecily Grzywacz, GCI scientist, and Jan Wouters of Royal Institute for Cultural Heritage, Belgium, for the GCI's Asian Organic Colorants project. In addition, several sets of commercial materials were exposed, including Windsor and Newton gouache paints and Dr. Ph. Martin's watercolors. Initial results from this trial indicated a smaller color change in the anoxic environment for most samples, but again the tests identified several materials for which anoxia proved disadvantageous.

Results from the first trial were discussed at the 2008 ICOM-CC Triennial Meeting in New Delhi, India, with presentation of the second exposure results at the AIC Annual Meeting in Los Angeles in 2009. Future work will build on this earlier research by duplicating the exposures but substituting microfading through the glass-top of the display cases in both air and nitrogen environments. The earlier exposures employed halogen lighting at only moderately elevated light levels. The microfading experiments will compare the ability of the microfader to derive the same type of data.

Last updated: July 2010