I've formulated a gel peel intended for estheticians with:
20% Glycolic Acid
5% Salicylic Acid
20% Propylene Glycol
Theoretically this amount of propylene glycol and alcohol should be enough to solubilize the salicylic acid, and it does when formulated, but over time a lot of the SA form crystals in the gel.
Advice on how to fix this?