Any of a variety of fluids added to an offset press's fountain solution to reduce foam or bubbles that can interfere with the proper distribution of dampening solution. Antifoaming agents are commonly silicone-based fluids or emulsions (in particular, polydimethyl siloxanes) that either dissolve a surfactant more thoroughly in the fountain solution, or reduce the surface tension of the fluid to prevent bubbles and foam from forming. (See Fountain Solution.) Also referred to as a defoaming agent.
Antifoaming agents are also added to any printing ink likely to form bubbles during printing.