My main beef with this one is the definition of "glowing." These water beads do not glow in the dark (or anywhere else); they must be activated with a black light, at which point they will look like the picture above. That doesn't qualify for "glowing."
"This may be a good time to get into the way certain kinds of luminescence work. Luminescence is what it's called when something gives off light. The type of luminescence that Pinners seem to love the most is photoluminescence, which means that matter absorbs energy and then emits light either immediately or as a delayed process.
When you have a delayed release, you have something that glows in the dark. Glow in the dark paint and other items slowly let go of the radiation they have absorbed (I'm talking about light here, not nuclear fission), and that energy is seen as visible light. When the energy is gone, the object stops glowing. This type of luminescence is called "phosphorescence."
When the glow happens immediately, as soon as you apply the energy (and it disappears pretty much as soon as the energy source is shut off), you have fluorescence."
Since these beads require a black light, their reaction is classified as "fluorescence" rather than "phosphorescence," and according to the rules (which I may have made up), only phosphorescence can legally be referred to as "glowing" or "glowing in the dark."
As for how to make these, they're the same water beads from the previous "
Water Marbles" post, but instead of using just regular water, or even food coloring in water, these beads are soaked in water that has fluid from a highlighter in it.
That's it - that's the secret. You open a highlighter, you mix it with water, and you soak your
hydrogel beads in it. THEN you get a black light, because as you know from using highlighters, they don't glow in the dark. But they do fluoresce.