A client visited us last month and we were discussing painting on float glass. Peter mentioned that it was possible to check for the tin side of float glass with a drop of water. It’s true! You don’t have to use a UV lamp.
Float glass (normal window glass) is made by floating the glass on top of a molten tin bath. The side of the glass in contact with the tin bath picks up residuals from the tin and this will have an effect on your silver stains and may have an effect on your other glass paints. Best to check the glass before painting and plan accordingly.