http://www.savinggraves.org/education/index.htm Many of the sites I've looked thru this morning say use an non ionic detergent cleaner such as NP40, Triton X-100, Tween 20 or Photo Flo which is made by Kodak. They say it is available in conservation, janitorial and photographic supply houses. When I go to the cemetery I bring plain water, a soft unused paint brush and some wooden or plastic spatulas. My object, like most everyone here, is to do no harm. I start from the bottom and work up to avoid streaking which can be just as bad as the stains. It's a time consuming process. I wouldn't attempt it if you don't have the time or an adequate water supply. Stefanie