A cleaning technique used in archaeological conservation. Artifacts are placed in a chemical solution, and by passing a weak current between them and a surrounding metal grill, the corrosive salts move from the cathode (object) to the anode (grill), removing any accumulated deposit and leaving the artifact clean. The process of electrolysis works by passing an electric current through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction).