This is a black and white photograph printed on paper coated with an emulsion consisting of gelatin and silver salts. The type of silver salt contained in the gelatin emulsion determines what method of printing is used. Papers containing silver chloride are used for contact printing, whereas papers containing silver bromide are used for enlargements. Chloro-bromide papers, which contain a combination of the two silver salts, may be used for either method of printing. The two silver salts also produce different tones in a print. The tone of a gelatin silver-bromide print is generally neutral black while a gelatin silver-chloride print is bluish black or cool in tone.