Ferro?

Whilst we're on the subject of Evening Tweed (brilliant name, by the way), one of their members, Tom Rowe, made this piece using ferro fluid. I'd never heard of ferro fluid before, so I jumped on Wikipedia to learn a bit more about it. Turns out it basically a magnetic liquid (or rather, magnetic molecules supported a liquid substrate) that NASA developed to allow them to influence the movement of fuels in a zero gravity environment. So it respond to magnetic forces, and can kind of be moulded by applying magnets to varying degrees. Basically, it's the first step towards creating the liquid metal bad guy from Terminator 2.

Some people have done some very cool things with this stuff, such as Sachiko Kodama and Minako Takeno, who created dynamic the scuplture in the video above as part of their work Protrude, Flow. Amazing stuff.