DETERIORATION OF SURFACES EXPOSED TO ENVIRONMENTAL CHANGES
GUSTAV A. BERGER, & WILLIAM H. RUSSELL
OUR TESTS have shown that to protect canvas paintings from environmental changes, the following steps are required:
- Maintain as stable an environment as possible.A stable, unchanging environment is ideal for the preservation of paintings and most objects. Regrettably, this can not be achieved by most of the currently available cycling radiators, air-conditioners, humidifiers, and dehumidifiers. These devices might be helpful if the painted objects were isolated from the effects of cycling by enclosing them in additional “envelopes” or showcases (Thomson 1977; Stolow 1977).
- Cycling changes due to intermittent exposure to light should not be overlooked.Occasional artificial illumination such as lamps or reflectors, turning on and off the lights in galleries, or just changing daily light levels can cause considerable changes in the temperature and RH of the irradiated surfaces. Much of the damage attributed to photochemical action might actually be caused by the cycling effects of intermittent exposure to light.
- Avoid excessively high RH.This would eliminate stress peaks when the resistance of the painting (Tg) is low (Bresee 1986).
- Avoid overstretching of the canvas.This can be achieved by:
reducing the stress fluctuations in the canvasapplying new sizings, currently being tested, which reduce the stress fluctuations in the fabricsusing the self-adjusting, continuous-tension stretcher (Berger 1983, 1984). This special stretcher eliminates stress peaks and overstretching of the canvas while maintaining optimal tension, as demonstrated by our tests (Berger and Russell 1987)lining, or mounting on a solid support. This treatment increases the stiffness of the fabric support, reduces the effects of cycling by adding bulk to the painting, and shields the reverse of the painting from fluctuations of the environment. Good linings and mountings have preserved paintings in the past, and our stress tester has proven their effectiveness by repeated, unbiased measurements.
The continuous surveillance of the stress changes in the tested samples and the detection of alterations that occur in the material in response to environmental influences have provided an entirely new understanding of the mechanisms of aging and decay, not merely of canvas paintings but of all surfaces exposed to environmental changes.