Dd1 (4) has been having a jolly old afternoon with magik snow. I picked it up on impulse in hobby craft, thinking I might regret it. But she has been sat at the table for ages playing with some figure in it.
No idea what it is made of, but technically it keeps for a while, just spritz it up with a bit of water. Just thought I'd let you know in case you spotted it in the sales.