Fluorescent Purple Glow PowderThis phosphorescent pigment is purple during the day, bright purple under ultraviolet light, and glows bluish purple in the dark. All of the glow powders sold by Art 'N Glow are encapsulated which means that they can be used in both solvent and water based mediums. Some of our competitors sell non encapsulated powders that will deteriorate in water based mediums (such as acrylic paint medium). Specifications: Glow Time: 6 hours Size: 20 30 um (micron)