Retarder

(1) Generally, a component added to a composition to slow down a chemical or physical change. A slowly evaporating solvent may be added to a paint, varnish or lacquer to delay the set of the film after application and so improve the application properties, or to give a better film, e.g., one with improved flow, or a retarder may be added to plaster to retard its setting. (2) In flexography, gravure and heatset printing, high boiling solvent added to ink to slow the evaporation rate. (3) In letterpress and offset. See Antioxidant. (4) A material which in small amount added to a rubber compound retards vulcanization or slows down the activity of the accelerator. Specifically, phthalic anhydride and salicylic acid are retarders. The most valuable retarder is one which slows the vulcanization at processing and early curing temperatures, but does not affect or may even activate the rate of cure at full curing temperatures. Syn: Inhibitor. (5) A chemical that, when added to the dyebath,...