Making glow-in-the-dark Strontium Aluminate:

Important disclaimer: Several of the reagents used here are very corrosive and can produce toxic gasses. If you try to repeat this, at the very least please wear eye protection — no project is worth permanent blindness.

The undisputed king of glow in the dark materials is Strontium Aluminate (SrAl2O4) which glows brightly for hours after exposure to light. Even better, all the components are fairly easy to get: Oxygen is everywhere, Aluminum is quite common, and while Strontium sounds exotic, it’s rather easy to buy for making ceramics.

Because it’s nearly impossible to mix metal oxides on an atomic level, strontium aluminate is usually made by decomposing soluble nitrate salts:

To make the aluminum nitrate, it’s not possible to just dissolve aluminum metal in nitric acid, so I first made some aluminum hydroxide from potassium alum (a food preservative):

To start, I dissolved some alum in water, and then added dilute sodium hydroxide to precipitate out aluminum hydroxide. This is what the product looked like after being filtered off and dried at 120 C to remove any traces of water:

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