Edging out the Competition

According to Brian Wenger, VP of GEW Inc., under-curing is seen when the ink or varnish is still tacky and full UV curing has not taken place. “Most press operators use an alcohol rub test whereby an alcohol soaked cotton swab is rubbed across the irradiated ink to determine if they are absorbed into the swab indicating under cure,” he says. “For varnishes, an aqueous solution of potassium permanganate is wiped across the varnish, which will oxidize any non-reacted varnish. An under-cured varnish will then darken depending on the degree of under-curing: the darker the test solution, the greater the under-curing.”