>> a rubber band feels cool after it is stretched and released Rubber is apparently a rare substance that shrinks when heated rather than = expanding. As a result, you can build a number of interesting gadgets. Search "rubber= band heat engine." BillW --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .