Coffee stain on textiles. Mechanisms of staining and stain removal

Coffee stains on textiles are mainly caused by the water-soluble and acidic colored substances in coffee. The acidic nature of coffee stain has been shown by ultraviolet and visible spectroscopy of coffee as a function of pH; ion-pair formation with a cationic surfactant and titration with Hyamine 1622 and a surfactant-specific electrode; and precipitation of the colored components in coffee with barium hydroxide as a barium salt. The permanence of coffee stains on textiles depends on the nature of the fibers. The affinity of coffee stain to fibers, indicated by resistance to detergency, increases in the order polyestern-nonanoyloxybenzenesulfonate, or Oxone® (DuPont, Wilmington, DE) obeys pseudo first-order kinetics. Oxone, a peroxysulfate triple salt, is a more powerful oxidant for coffee stain than sodium perborate, but its use is limited by the bleach fastness of dyes.