Rainbow ink is a solvent-based, metallic formulation from Pröll that’s designed for creating iridescent color effects on a variety of substrates. The ink can be printed onto clear PC, PMMA, rigid PVC, and pre-treated PET films, when printed on the reverse side of the substrate. The company says that first-surface printing also can produce unique effects. The ink is available in four shades: Rainbow Ink 10/100 (fine pigments), 10/50 (fine pigments), 35/100 (coarse pigments), and 35/50 (coarse pigments). Proell Inc., 2751 Dukane Dr., St. Charles, IL 60174, 630 587-2300, fax: 630-587-2666, Web: www.proell.de.