Removing Puzzle Pieces Stuck to Glass

Dear Donia,
How do I safely remove puzzle pieces that are stuck to glass in a frame?

Framed Puzzle

Q. Dear Donia,

I have a framed puzzle which unfortunately sustained some water damage and as a result has become moldy in a few spots. In my attempt to remove the puzzle from the frame and clean it up, some of those moldy spots have stuck to the glass. Any suggestions as to how I might remove the puzzle without ruining those pieces which are stuck? Thanks, Shannon

A. Dear Shannon,

It is unfortunate that your puzzle got wet and then moldy. It is very difficult to remove items that are stuck to glass because the mold has damaged the paper substrate and also changed the composition of the paper. It is also difficult to remove puzzle pieces on glass if it is a more modern puzzle. These puzzles would use a clay coated paper to give the glossy finish on the image side and clay coated paper gets very sticky when wet and adheres itself to whatever it is adjacent to.
Before attempting to remove the puzzle pieces, I would get a good scan of the puzzle so that if any irreparable damage occurred, you still have the image. Then I would first attempt to remove the stuck pieces with a very thin metal spatula (similar to one that you use for icing cakes or used in palette painting) to see if they will pop off. If they won't, then about the only option is to try to use moisture to get the pieces to loosen. Use a brush (a flat or fan style artist's brush) to slowly apply water between the piece and the glass and use the metal spatula to try to separate the pieces. Once separate, be sure to get the pieces dried as quickly as possible to prevent the mold from reactivating.
Separating items from glass is very tricky to do so if you do attempt it, please work very slowly and carefully.
Thanks for asking Dear Donia!