A state of reduction or removal of halation. In the collodion process, photographers placed red paper or cloth behind negative plates in the holder. Doing so made light reflect from the back of the plate to cast a nonactinic color, preventing reexposure of the plate. In gelatin plate work, the backs of plates were coated with a red, orange, or yellow pigment in a water-soluble gum base. See also Aurin.