On February 29, 1996, there was an internal meeting at the Canadian Conservation Institute to discuss accelerated aging research. Summaries of staff members' presentations were published in the September 1996 CCI Newsletter. Since no more recent report of this research exists, and since the preliminary results sound significant, four of the summaries are reprinted here with permission of the CCI editor.
Paul Bégin discussed the accelerated aging of paper, particularly the stack-versus-single-sheet phenomenon. CCI has evidence that the properties of paper aged in stacks rather than in single sheets resemble those of naturally aged materials more closely. Tests will be performed at CCI to determine if this stack effect holds true as the accelerated aging conditions approach ambient conditions (23° C and 50% RH). Paul also discussed the moisture content of paper aged at higher temperatures; the relative humidity is increased at higher aging temperatures to keep the moisture content the same as it is at ambient conditions.
Extrapolating edge effects in paper
Stefan Michalski spoke on extrapolating edge effects in paper when volatile intermediates are involved. Compared with room temperature, high temperatures increase production of intermediate volatile species such as acids more than they increase the rate of diffusion of these volatiles out of the stack. It appears from approximate calculations that at room temperature, diffusion of degradation products out of a stack of paper (such as a book) is more rapid than reabsorption and reaction. At higher temperatures, the reverse may be true--but at present the experimental data on this point is very limited.
Season Tse discussed accelerated aging and textile conservation research. In the past, CCI textile research has concentrated mainly on cellulosic textiles. The method of artificial aging used was thermal/humid aging. With a new priority to study protein fibers, Season plans to use artificial aging for the preparation of a series of samples for analytical method development, for the pre-aging of new samples prior to treatments, for the aging of samples after treatment, and for evaluating the light fastness of certain dyes. Methods of aging will include chemical tendering, thermal aging at different temperatures and light aging using a quartz-halogen light rack. The plan to build and age samples in a quartz halogen light rack is based on the fact that many museums are using these lamps for exhibition and some of the traditional fluorescent tubes will no longer be used in museums because of the new energy efficiency regulations (Michalski, CCI Newsletter No. 17, March 1996). Aging samples with these lamps will more closely approximate museum conditions.
Gregory Young spoke about possible alternatives to accelerated aging such as using sensitive microanalytical techniques for monitoring natural aging over a period of few years. He mentioned several instrumental methods of analysis currently available at CCI. Such alternatives should perhaps be considered first during the design phase of aging research.