Q. Most municipal water is treated with chlorine and fluoride, but a lot of private wells are individually chlorinated to achieve the same water quality. Does chlorine have a deleterious effect on watercolors? If so, how much chlorine can be introduced into the water before it has a negative impact?
A. The chlorine content of a typical municipal water supply is on the order of 1.5 ppm (parts per million)—a negligible concentration. If this were an alarming concern we would have noticed problems with contemporary watercolor paintings, and artists and conservators would have already raised the issue.
I can offer two solutions if youre still concerned. First, put your tap water into a wide-mouth jar and let the chlorine evaporate out overnight. (Chlorine is a gas.) Or, second, you could buy distilled water at your local supermarket and use that instead.