Usually our 5-Minute Projects involve soldering and LED lights and other such electronic accoutrements, but this week we decided to skip the fancy stuff in favor of an old-school science project: making rheopectic slime from Borax and glue. This is a pretty safe experiment even for kids–just make sure to do it with parental supervision and keep the Borax, slime, and any fingers that have been touching the aforementioned items out of eyes, noses and mouths.

The neat thing about rheopectic slime (besides the impossible-to-resist gag of fake-sneezing into your hands and then showing the flowing goo to your revolted victims) is its non-Newtonian fluid property. Most fluids get less viscous the more you manipulate them–think of how honey or oil become “wetter” as they warm up and more solid as they cool. Those are Newtonian fluids. But non-Newtonian fluids do they opposite: they get more solid the more they’re manipulated. So if you let this slime sit on a surface, it will pool out into a flowing mess, but if you play with it, it becomes thicker and bouncier. You can even form it into a ball.

Watch the video to see how it’s done: use more Borax to make a stiffer, bouncier slime, and use less to make Ghostbusters-style “ectoplasm.”

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