Liquid Gypsum

Hello, I'm looking for any type of acid that can remove a film of glaze gypsum product created from the mold, so to get a result u or matt cutter about it. There should be some kind of liquid, I think it's an acid wash of the film that was created when the plaster has been hardened in the mold. Thnx for your help

Did you know they put in plaster twinkies?

Help Sorry but i cannot.