Acid Dip. A method of cleaning metal by immersing in a mild acid solution. It is used in medallic work as a bright dip, certain finishing operations, or in cleaning. Also called acid bath. See pickle, pickling.CLASS 09.3 This unusual acid-etched medal was made by photoetching from black-and-white images. Etched on one side of an aluminum sheet, it is turned over for etching the reverse with exact positioning. Numerous pieces are arranged on a large plate. Color is added by paint in the sunken etched areas. It is not a popular method of medal manufacture.
Source: D. Wayne Johnson Encyclopedia of Coin and Medal Technology