The collotype is closely related to other photographic processes that rely on ability of gelatin to become hardened after being sensitized and exposed to light. In practice, a sheet of glass is coated with gelatin that has been made sensitive to light. It is then exposed in contact with a photographic negative. Where the greatest amount of light reaches the glass plate, the gelatin becomes the hardest. The less hard parts of the gelatin image are then washed away in a bath of warm water. The plate is dried and dampened with water and glycerin with the non-hardened areas absorbing the most water. Ink is then applied to the plate with the parts of the image that have absorbed the most water repelling more of the ink. The end result is an image that looks somewhat like a silver gelatin print. Before the advent of offset printing the collotype process was used extensively to create postcards, albums for tourists, posters, and for some fine art applications. The Albertype Company of Brooklyn, NY produced over 25,000 collotypes before its closure in 1952.