Leaded glass, commonly referred to as stained glass, is a type of multi-colored glass with colors separated by a thin lead layer. When cleaning this glass, it is important to use a safe cleaning technique that will remove residue and dirt without damaging the colored glass. Abrasive commercial cleaning products will eat through the color, but you can make your own mild cleaning solution.
Step One
Wipe the glass regularly with a feather duster to wipe away dirt as it accumulates.
https://letsfixit.co.uk/15083/how-to-clean-leaded-glass/?utm_campaign=twitter&utm_medium=twitter&utm_source=twitter