Stepping stones that glow in the dark make a helpful and attractive addition to a dark pathway. They also don't require electricity, which makes them useful in areas where there are no electrical outlets. The phosphorescent chemical in them recharges in normal daylight conditions, and can glow in the dark for anywhere from about 30 minutes to 10 hours. They can be somewhat expensive to make yourself because the earth aluminate phosphors used in most glow powders are somewhat rare.
Glow-in-the-dark powders can be added to concrete that is being used to make stepping stones. The recommended amount is about 15 percent powder by volume to be mixed with the concrete. The exact amount used will depend on the specific type of glow powder that you obtain, and the directions should be available from the manufacturer. Powders made with earth aluminate tend to light much better, and the light lasts much longer than those with a zinc base.
When constructing tiles using a mosaic method where grout is used, the glow-in-the-dark powder can be mixed in with the grout. This will result in a glow over much less of the surface area, but should still produce a satisfying result, especially if earth aluminate powder is used. This is a handy method to use if you do not want as much light in the area as you would get if the entire stone glowed. When using grout that requires a sealant, make sure the sealant does not contain any agents that block ultraviolet light. The glow-in-the-dark powder requires exposure to UV light to activate the phosphorescent properties.
Paint is best purchased from a company that specializes in glow-in-the-dark products. Attempting to mix glow-in-the-dark powder into normal paint most often does not produce the desired results. This is because normal paints often contain UV barriers that block the light required for activation of the phosphors. Paints also do not have the right suspension properties to distribute the glow powder evenly throughout the paint, and subsequently on the painted surface. The paint pigments can interfere with the amount of light that the pigment is exposed to and can greatly increase recharge times for the phosphors as well as decreasing the amount of light that is given off. The earth aluminate powders that produce the best and longest-lasting glow do not mix well in water-based paints, so avoid these if you want a longer-lasting glow unless they specify that the aluminates have been specially coated.