Materials: yellow highlighter marker, 1 cup clear washable school glue, 1 tsp. Borax (a laundry booster; we find it at Wal-Mart in the laundry aisle), water, 2 bowls, spoon, food coloring, plastic spiders, black light (black light bulbs are widely available around Halloween).

Procedure: To make fluorescent water, carefully cut open your highlighter, pull out the soft ink insert, cut it open, and soak it in 1 cup of water for about 10 minutes. While it’s soaking, pour 1 cup plain water into a bowl. Add 1 tsp of Borax and stir until dissolved. In a second bowl, pour the 1 cup of fluorescent water. Add 1 cup clear glue to the fluorescent water and stir. Pour the Borax solution into the watery fluorescent glue solution and stir. Add as many spiders as you would like to your slime and enjoy! To make your slime glow, head into a dark room (or make your own bat cave!) and shine a black light on the slime.

The Science: The school glue we used in our solution contains a polymer called polyvinyl acetate. When we add Borax to the glue, the polymer chains in the glue are linked together creating something that looks like a net or spider web. This is called a “cross-linked polymer” which is stretchy – like slime!

Your slime will glow under a black light because it contains phosphors extracted from the highlighter ink. Phosphors are chemicals that absorb then release energy from light. The glow can last from a few milliseconds to up to a few hours. When the phosphors release the light quickly, this is called “fluorescence.” When phosphors release the light slowly and create a lingering glow, this is called “phosphorescence.”

Using a black light is a great way to demonstrate phosphors. A black light emits ultraviolet radiation type A, or “UVA” radiation. This is similar to the ultraviolet radiation type B (“UVB”) that comes from the sun, but is not harmful. (When you look at a black light, you will see a purplish glow, but this isn’t the UVA radiation. The UVA radiation is there, but it is invisible.) When UVA radiation shines on things containing phosphors, the phosphors absorb the invisible light and turn it into visible light. A fluorescent toy will only glow while the black light is actually shining on it; it won’t save up the light and release it over time like a phosphorescent toy. This is the case with our glowing slime: it is fluorescent and will only glow while under a black light.