The hydroxamic acid and the named salts thereof have the ability to dissolve gypsum, and also the ability to convert gypsum not actually dissolved into a water dispersible sludge.

How do you dissolve gypsum powder?

Looking at Sinkankas' book, he says gypsum is soluble in hot dilute hydrochloric acid. Googling around, I also see warm salt water, warm sugar water, and citric acid being recommended for removal of gypsum scale, which is a widespread problem.

Can you dissolve gypsum in water?

Gypsum is somewhat soluble in water, but more than 100 times more soluble than limestone in neutral pH soils. When applied to soil, its solubility depends on several factors, including particle size, soil moisture, and soil properties.