Copper Sulphate Crystals have a long history of use as an etchant for zinc in printmaking. While their use has been attributed to historic figures such as Goya, this remains unverified. In more recent practice, particularly from the 1990s onwards, copper sulphate gained renewed attention as a safer alternative to nitric acid, supported by printmakers, including Cedric Green and Nik Semenoff. Its development was later extended by Friedhard Kiekeben into the Saline Sulphate Etch for use on zinc, aluminium and steel.
Used on its own, a copper sulphate solution will etch zinc effectively. Adding sodium chloride improves both the efficiency and lifespan of the solution, making it more consistent in use. It remains a widely adopted option in studios seeking lower toxicity approaches to metal etching.