Mystery blue & white beads

The blue and white bead bottle up there might look familiar to a lot of science teachers, especially the ones who have taken our ASM summer camps. The bottle can be bought from Educational Innovations or from Flinn Scientific (though Flinn's version is green and white).

The bottle is a spectacular demonstration of density and of solubility, both of which are explained by Steve Mould in the above video.

We do a similar activity in a lab in our material science course at Princeton (one we certainly didn't develop but have tweeked to our needs) using preforms and polymer pellets. An extension we particularly like is related to the food coloring demo that Mould mentions in passing near the end. I especially recommend green food coloring. The effects are far more dramatic than the red that Mould shows.

Another extension involves shining ultraviolet light at the bottle. It turns out that - as one of our Utah campers pointed out to me after I'd had the bottle for a decade or so - that the white beads are actually the UV beads that Ed Inn sells. Apparently having a classroom with no windows blocked me from seeing that happen until she pointed it out to me.

I did also find a video showing how you can make one of your own - without the UV beads, however. The YouTuber's full instructions with quantities can be found in the video description.

I'll copy the video description, however, in case the video experiences link rot...

"Sorry for the spelling mistake in one sentence!

Water and Isopropyl alcohol are SOLUBLE with each other. (solvable is wrong word)

Poly Density Bottle

Take any size bottle, divide number of ounces of the bottle into half. Half number of ounces distilled water and half number of ounces 91% Isopropyl alcohol.

I used 50oz bottle.

So I added 23oz water and 23oz Isopropyl alcohol.

Salt 1tsp for 1oz of water.

So I mixed 23tsps of Salt in water.

Not filling the bottle completely and leaving some space for air at the top is a good idea.

Easy to shake and mix liquids.

Beads 260 of each kind.

You can add or minus number of beads according to the size of the bottle."