The classic "glow in the dark" or phosphorescent pigments consist of very fine crystals of zinc sulfide. Copper is added to the zinc sulfide as an activator. This allows the crystals to absorb light and slowly emit it over time. The slow emission is called phosphorescence.
6SSU is the basic phosphorescent pigment. This material has a light yellow (natural) body color and a yellowish green afterglow. 6SSU is designed to give the brightest and longest afterglow. Six colored phosphorescent pigments (the GSS Series) are also available. These are manufactured using a proprietary process which combines 6SSU with daylight fluorescent pigments. This result is a pigment with a distinct daylight body color and a variety of bright emission colors.
GSR is a recently introduced yellow emitting (glowing) pigment also consisting of very fine crystals of zinc sulfide. GSR is activated with small quantities of copper and manganese bound to the molecule, causing the "glow in the dark color" to shift to yellow. The major application of GSR is as a base pigment to effectively improve the "glow in the dark" emitting colors of yellow and orange daylight colored phosphorescent pigments. For example, GSR 115/2 Orange which has a bright orange afterglow has been specially developed for Halloween. GSR 115/2 Orange is shaded with a heat resistant fluorescent pigment so it can be used for plastics as well as general ink or coating applications.
BAS is a newly introduced "blue emitting" phosphorescent pigment. BAS consists of fine crystals of calcium and strontium sulfide activated with bismuth causing the "glow in the dark" color to be blue and the body color to be white. Its major application is as a base pigment to effectively improve the "glow in the dark" emitting color of blue daylight colored phosphorescent pigments. BAS 5025/1 Blue is an excellent example of such an application.