Copper sulfate (CuSO₄) is a fining agent used to remove unpleasant hydrogen sulfide (H₂S) and other "sulfide-like" off aromas in wine. The hydrogen sulfide is generally described as rotten-egg-like off aromas.H₂S is volatile natural product of the fermentation and it can be present into the wine as mono-mercaptans (sulfides), which can be treated with copper or poly-mercaptans (disulfides) which will not react with copper, so deal with the problem as soon as it is detected. Copper when added to wine containing "sulfide-like" off aromas immediately reacts with H₂S and form copper sulphide, immediately. If the copper ions is not removed from the wine after the treatment with the proper fining agent or filtered out, a haze may appear. Most of the time copper is added to the wine in the form of Copper Sulfate s(CuSO₄•5 H₂O), also known as Copper Sulfate solution.

To avoid over adjustment, copper lab trial should be performed.