ИСТИНА

Toning is a process giving a possibility to change black or grey colour of a print as a result of a transformation of image silver into colored chemical compounds or a dye. Dyeing of photographic image into sepia (different hues of brown from purple brown to yellow brown) is usually made by a transformation of metallic silver into silver sulfide with the use of sodium sulfide, thiourea or other sulfur-containing compounds. By converting metallic silver into colored metal salts is possible to change a black and white image into many different colors. Thus, toning by salts of iron gives the image dyed in blue, by salts of uranium - in red brown, by salts of copper - from pink orange to dark cherry, by salts of nickel - in bright red, by salts of lead - in yellow. To obtain some colours and their hues several salts of different metals are used simultaneously, e.g. to obtain green salts of iron and lead are used.