The gelatin silver process was introduced at the end of the nineteenth century and dominated black-and-white photography in the twentieth century. The paper or film used to make gelatin silver prints and negatives is coated with an emulsion that contains gelatin and silver salts. Gelatin silver prints and negatives are developed out rather than printed out, which means that exposure to light registers a latent image that becomes visible only when developed in a chemical bath. This process requires shorter printing times than earlier printed-out processes such as salted paper prints and albumen prints. George Eastman’s introduction of flexible roll film and the Brownie camera revolutionized photographic practice and industry, putting photography into the hands of the masses for the first time. This process is responsible for all the black and white, color and motion pictures produced in the 20th century with analog materials.
Video from the Eastman House Museum