Calx is also known as calcium hydroxide, hydrated lime, or slaked lime. It serves as an alkali in many dye recipes.

Calx is used in indigo fermentation vats and serves to raise the ph level helping to dissolve the indigo and aid in the reduction of indigo. Calcium hydroxide is also an ingredient in Nori paste (Japanese rice paste resist). It causes the starch in rice flour to swell and give the paste body. It also acts as a preservative.