Process for producing fluorescent or phosphorescent pigments coated with glass

摘要

A thick glass coating protects fluorescent or phosphorescent pigment particles from greying or fading due to service conditions, such as photochemical reactions. The pigment particles are mixed with a finely ground heavy metal-free glass in a ratio of approximately 5 parts glass to 1 part pigment. The pigment and glass mixture is then heated to a point where said glass is softened to such an extent that the pigment particles are surrounded by the glass. The glass is thereafter comminuted into a granulate consisting of a plurality of small glass bodies. The granulate is reheated so that pigment particles exposed by the comminuting are resurrounded by the resoftened glass. The glass pigment mixture can alternatively be suspended in a liquid and poured into a mold before heating in order to form glass bodies having a particular shape.