Umesu, which contains citric acid as the main component, was used for metal plating and soldering and the oxidation coating treatment of bronze and iron ware (copper oxide (II) and iron oxide (II), an anti-rust treatment using an oxide film made of ferrous oxide called "kurodome"), in addition to the sterilization of tools and bodily wounds.
また、クエン酸を主成分とする梅酢は器具や人体の傷口の消毒の他、金属のめっきやはんだ付け、青銅器・鉄器の酸化皮膜処理(酸化銅(II)および酸化鉄(II)：酸化第一鉄による『黒留め』と呼ばれる酸化皮膜による防錆処理)のためにも用いられた。