There has always been a fascination with glow in the dark phosphors, and the market for consumer products is quite large. The applications are very much varied from decoration to safety. And, manufactures have made a number of materials phosphorescent, from glow in the dark safety tape, to paint that can be used at home.
First, what is a phosphor and how does it work? Let's look at at a familiar concept to answer the question. A phosphor is a chemical that absorbs light in one frequency, or wavelength,and stores it as energy. It then releases that energy over time at another wavelength, or color. A good example is a fluorescent light familiar as a tube. It is a gas discharge tube that electrically excites mercury vapor to produce ultraviolet energy. The inside of the tube is coated with a phosphor that is quick acting, and converts the UV to a blue-white color. This is how the light is generated. But, there are slower release chemicals that store energy for a longer time. Zinc sulfide is one of the oldest materials that exhibits phosphorescence. It absorbs light in mostly the blue end or ultraviolet area of the spectrum, and releases its energy over time as a yellowish-greenish color. The problem with zinc sulfide is that it has a fairly weak color saturation, and a relatively short glow time. But, there are several newer materials that are available that have brighter color, and glow for ten times as long. Of particular interest is strontium aluminate. It is also greenish in color, and can glow for 8 to 10 hours after being exposed to light.
First, what is a phosphor and how does it work? Let's look at at a familiar concept to answer the question. A phosphor is a chemical that absorbs light in one frequency, or wavelength,and stores it as energy. It then releases that energy over time at another wavelength, or color. A good example is a fluorescent light familiar as a tube. It is a gas discharge tube that electrically excites mercury vapor to produce ultraviolet energy. The inside of the tube is coated with a phosphor that is quick acting, and converts the UV to a blue-white color. This is how the light is generated. But, there are slower release chemicals that store energy for a longer time. Zinc sulfide is one of the oldest materials that exhibits phosphorescence. It absorbs light in mostly the blue end or ultraviolet area of the spectrum, and releases its energy over time as a yellowish-greenish color. The problem with zinc sulfide is that it has a fairly weak color saturation, and a relatively short glow time. But, there are several newer materials that are available that have brighter color, and glow for ten times as long. Of particular interest is strontium aluminate. It is also greenish in color, and can glow for 8 to 10 hours after being exposed to light.
When I saw both the water-based latex glow paint from Rust-oleum, and the acrylic-based spray from Krylon, I was hoping that the phosphor being used was the strontium aluminate. But, neither container had the phosphor listed on the label, so I took a chance and purchased both for about $8 each.
I then followed the manufacturers instructions to the letter and expected at least reasonable results. The latex was coated on white foam board with six coats, and the spray with six light coats over a prepared piece of aluminum painted white as the instructions stated. Despite the carefully followed directions, the results were terrible. The two test pieces failed to glow after 8 hours in sunlight, or 10 hours under a fluorescent bulb. There was simply too little glow to even photograph the results. The only way to get any glow was to illuminate the samples with blacklight. And, as the photo will show, the glow is irregular, and looked like it was poorly mixed. The phosphor used is clearly zinc sulfide and had not lived up to the package claims. My recommendation is to look for a glow paint that has the strontium aluminate, even if it costs more. Both packages advised that if I was dissatisfied, let them know. I am working on two emails right now! In the photo below, the latex is on the left.
I then followed the manufacturers instructions to the letter and expected at least reasonable results. The latex was coated on white foam board with six coats, and the spray with six light coats over a prepared piece of aluminum painted white as the instructions stated. Despite the carefully followed directions, the results were terrible. The two test pieces failed to glow after 8 hours in sunlight, or 10 hours under a fluorescent bulb. There was simply too little glow to even photograph the results. The only way to get any glow was to illuminate the samples with blacklight. And, as the photo will show, the glow is irregular, and looked like it was poorly mixed. The phosphor used is clearly zinc sulfide and had not lived up to the package claims. My recommendation is to look for a glow paint that has the strontium aluminate, even if it costs more. Both packages advised that if I was dissatisfied, let them know. I am working on two emails right now! In the photo below, the latex is on the left.
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