JAIC 1997, Volume 36, Number 3, Article 3 (pp. 207 to 230)
JAIC online
Journal of the American Institute for Conservation
JAIC 1997, Volume 36, Number 3, Article 3 (pp. 207 to 230)

FURTHER STUDIES ON TRANSPARENT GLAZE FADING: CHEMICAL AND APPEARANCE KINETICS

PAUL M. WHITMORE, & CATHERINE BAILE


ABSTRACT—The light fading of transparent glazes is described from two perspectives: first in terms of the colorant loss from photochemical reaction, then in terms of the color changes that result from that colorant loss. The authors postulate that if the rate of colorant loss depends only on the amount of light absorbed at the photochemically active wavelengths, then the results of light exposure of dark and pale glazes should be very different. The loss of colorant in highly absorbing glazes should be constant with exposure, but only minor spectral changes that cause slight hue and chroma changes are produced. In paler glazes that absorb less light, colorant loss from light exposure should be slower than for dark glazes, and it should also become progressively slower as colorant is lost. Despite this slower colorant loss in pale glazes, large spectral changes result, giving rise to the large chroma losses and value increases that are the changes normally associated with fading paints. The general trends predicted by this simple model were observed in fading experiments of Pigment Red 66 glazes. Although some discrepancies from the idealized fading behavior were observed, these trends are suggested as a starting point for identifying glaze applications that may be at high risk of light-induced damage and may thus warrant special care or condition monitoring.
[Spanish Abstract] [French Abstract]

Article Sections:

1. INTRODUCTION
2. THE OPTICS AND APPEARANCE OF TRANSPARENT GLAZES
3. THE PHOTOCHEMISTRY OF GLAZE FADING
4. APPEARANCE KINETICS OF GLAZE FADING
5. SUGGESTIONS FOR MONITORING THE COLOR STABILITY OF GLAZES
6. CONCLUSIONS
1. APPENDIX 1
2. APPENDIX 2: EXPERIMENT
a: Appendix , Materials , References , Author Information
Entire Article

Copyright 1997 American Institute for Conservation of Historic and Artistic Works