>Other thoughts:
>Concrete containing expanded polystyrene (styrofoam) 
>is already fairly common.
>Maybe you could just add some baking soda to your concrete? ;-)

Well, I was thinking of ping pong balls ...
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist