To chemically treat a lithographic plate to impart to non-image areas water-receptivity and ink-repellency, commonly utilizing a solution of gum arabic or other gum compound. It is the offset press fountain solution that keeps the plate properly desensitized over the course of a print run. See Plate: Offset Lithography. (See also Fountain Solution.)
In photography, a substance used to decrease the sensitivity to color of a photographic emulsion, to facilitate development under relatively bright light.