First we need to look at how stained-glass windows are constructed before we can look at how to best maintain them. Stained-glass windows are made up of cut pieces of glass, grooved bar of lead for holding together the pieces of glass in windows of latticework or stained glass. Windows that most people call stained glass are actually made up of pieces of coloured glass. The individual pieces of glass are cut and pieced together to form a design. The frame around each piece of glass is called cames. The cames are wired to the bars at strategic intervals so the weight is transferred to the bars and sashes.
Before trying to clean or repair a leaded glass window, make sure that all the glass looks in good shape. Be sure the cames are wired to the support bars well. If any of the wires are lose, you can twist to tighten. If the window has a bulge away from the bar, it should be looked at by a professional.
The cames made up of lead or zinc if it is in good condition should have a uniform grey colour. A white powder on the surface means that the metal has oxidized and has reached the end of its life. Metal that cracks or breaks should be replaced. Repairing came should be done by a experienced professional.
Sometimes the came is in good condition but the filler cement has dried up and fallen out over time. Resulting in a noticeable gap between the came and the glass. Re-cementing of a leaded-glass window can be done yourself.
Use a good quality glazing compound for this it should be tinted to match the colour of the came. Mix a little lamp black into the compound, and manipulate it to distribute the colour. Push toward the came and not against the glass. Scrape the excess compound.
To clean the stained glass window use a solution of warm water and a neutral pH soap. Apply it with a soft cloth. Do not use a commercial window cleaner on leaded glass because they usually contain ammonia, which can cause a reaction with the cames.