In mainland China, gypsum (calcium sulfate) powered and dissolved in the water is used as a coagulant; however, in the Japanese traditional process used since ancient times, bittern resulting from the process of salt production was mainly used.
大陸中国では石膏（硫酸カルシウム）を粉末とし水に溶いたものを凝固剤とするが、古来の日本の伝統的な製法では製塩の過程で生じるにがりが主に使われていた。