The Effects of Acid Rain on the Visible Light Absorption of Stained Glass

Abstract
The effect of acid rain on stained glass windows is felt by many churches and other
historic buildings worldwide, especially in Europe. As a result, the relationship between the
traditionally dark interiors of these European churches and the acid rain that corrodes the stained
glass was studied. Specifically, the effects of specific pHs of acid rain on the visible light
absorption of stained glass over time were examined.
In order to study this topic, various samples of modern stained glass were exposed to
acidic solutions at specific pHs. The visible light absorption of these samples was measured
using an Ocean Optics Chemistry USB 4000 NIR-VIS spectrometer over a period of eight
weeks, with one absorption measurement per week. These absorbance spectra were then
compared to analyze the specific impact of pH on the samples of stained glass.
It was found that pH affects the visible light absorption of stained glass in three main
ways. First, after breaking through an initial outer layer on the glass, the visible light absorption
of stained glass will continue to increase as it is exposed to acidic solutions over a period of time.
Second, the lower the pH of the acidic solution that the samples of stained glass are exposed to,
the higher the visible light absorption of the samples of stained glass. Finally, a greater change
in the pH of the solution over the course of the experiment lead to a greater change in the visible
light absorption of the samples exposed to that solution.

Francis Ricci

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