Watermark electrotype An electro-type is a light watermark in which the color has been'strained' to produce a striking contrast with the surrounding surface. This permits it to be easily read but makes forgery tough. Electrotypes are used primarily for mass production of printed material, such as postage stamps and banknotes. Electrotyping involves using a stencil or master to apply ink to paper or other materials. The ink on the material is made into an electrotype by passing the material through a series of baths containing salts that will dissolve or disperse the ink molecules. The resulting mixture is then molded under pressure into small cubes about one inch on each side. These in turn are placed in an acid bath to remove any remaining salt and then washed thoroughly with water before being dried. The process can be repeated as often as necessary to obtain the required depth of type. For example, an eight-part typeface might require up to four sets of molds. Each set of molds will produce identical pieces, which are then used to print a single copy. Once these copies have been printed, they are removed from the machine and either destroyed or stored for future use. Electrotypes were first produced around 1872. They quickly became popular because of their ease of use: anyone with a little training could operate the machine.