KPR, originally known as Kodak Photoresist, is a photosensitive material used in photoengraving, Photogravure and photolithography. Once dried, KPR can be dissolved by several solvents. However, after exposure to strong ultraviolet light, it hardens and becomes insoluble by some of these solvents. It is also resistant to acid, ferric chloride and other chemicals used to etch metals.