The true story of Purple of Cassius

Abstract

For the past 300 years the literature on gold, on glass and on ceramics has ascribed to Andreas Cassius the credit for discovering the purple preparation of colloidal gold and slannous hydroxide that bears his name and that is still in use as the most effective means of producing enamel colours ranging from pink to maroon. But not only was it known and described more than 25 years before its publication by Cassius; it had already been successfully used to produce a beautiful ruby glass.