This pigment is not permitted for use in cosmetics in the USA per the FDA.
Without the addition of other pigments, the glow powders will glow for up to 8 hours; however, you can add pigments to the glow powders. While it will reduce the glow time, it will also change to or add to the effect.
The most intense luminescent effect will come from the larger particle size powders, but for a smooth even finish on your product, you should go for the the smaller particle sizes. Sea Glow is 15-25 mm in particle size.