Grabado en metal: La alquimia del reciclaje. Intaglio: The alchemy of recycling

The chemical reactions involved in the etching process of iron and aluminum plates treated with saline sulfate mordant are described. In both cases, the cupric ions of the mordant are reduced to atomic copper, that precipitates as a reddish sediment, while the metal of the plate is ionized and dissolved, so etching the plate. Therefore, the metal ions extracted from the plates of iron or aluminum, reacting with the chloride in the solution, producing ferrous chloride (FeCl2) or aluminum chloride (AlCl3), respectively. The former is the chemical precursor of the mordant for etching copper plates, which only needs an additional oxidizing process to be transformed in ferric chloride (FeCl3). Meanwhile, the aluminum chloride is a precursor of alumina, a common component of the ceramic pastes.