I have the 'original' polydensity kit from Ed Inn (now Flinn, blech), and it's a fascinating toy.
Two insoluble liquids and two types of beads - pony and UV - which make for some fascinating behavior when the bottle is shaken and allowed to settle and separate.
In today's video, Steve Mould attempts to make a similar bottle with three insoluble liquids and four polymer beads.
He does achieve his desired result by the end, but the beads he uses look to be a little tougher to source.
Sadly so...
