Slime science fair projects: why not, and what to make instead

The rule

🔊 Kitchen chemicals only, in small amounts. Elementary rules allow safe household things such as baking soda and vinegar, and ban dangerous chemicals. One rule set limits a safe chemical to under a tablespoon on display.

Borax is on the list of words no Peabody project may say. The Workshop's slime uses contact-lens saline whose label lists boric acid and sodium borate, the same kind of chemical as borax, and a grown-up measures and pours it, so it stays off the fair's list too.

Sources: Washington County School District (Utah), district science fair rules (October 2011); Lowville elementary science fair rules. Your school's sheet wins. The rules in plain words has every shared rule with its source, and Is my project OK? checks an idea of your own.

Why, and what to do instead

Slime is great fun to make, and the Workshop has a stretchy slime build for exactly that. It just isn't a good fair project. The thing that turns runny glue into slime is a borate: it's in borax, and it's in the contact-lens saline that slime recipes without borax use instead. Peabody's fair projects use only what's in the kitchen cupboard, and the rule sets we read allow kitchen chemicals and ban dangerous ones. And making slime on its own isn't a test: a judge wants a question you answer by changing one thing and measuring what happens.

Oobleck is the closest swap. It's only cornstarch and water, it's gooey, it runs when you tip it slowly and jams when you poke it fast, and the project measures something real: how much cornstarch it takes to hold a penny on top. Magic milk gives you the swirls of colour, and the density tower gives you thick, slow, stripy layers of honey, syrup and soap. Every one uses things from the kitchen, and each changes one thing and measures it three times. Put a tray down: these are messy too.

• 🔨 Make Stretchy Slime in the Workshop (with a grown-up, for fun, not for the fair)