Oobleck

Oobleck made with a cup of cornflower/cornstarch and half a cup of water! This creates a suspension resulting in a unique material that can behave as both a solid and a liquid depending on the applied force! 

https://www.steampoweredfamily.com/how-to-make-oobleck-with-arrowroot-flour/#What_is_Oobleck

(Lots of science experiments on this web site). 

Warning it’s messy, but just allow to dry and hoover up? I sent it all down the sink but shouldn’t have!  Glad I used half proportions! 

Eldest remembered me doing it with them before.  I’d completely forgotten! So we did it again! 

Apparently you can do it with arrowroot too. That’s what I used last time, and some food colouring.