InstaMorph - Moldable Plastic I just discovered this stuff. It's a plastic that becomes putty-like in 140 degree water, then solidifies into normal feeling plastic upon cooling. It's amazing, and you can reuse it over and over. It's machinable just like regular plastic. I used it to make a mold and copy of a ratcheting ring that was missing in a hip joint. Luckily I had the other side to make a copy of. It was a simple mold that only needed one half, as the ring was flat on one side. I made the mold, cooled it and used some cooking spray on it to avoid sticking, and then I heated more instamorph and forced it into the mold. I wasn't sure if it would work as instamorph sticks to itself, but the cooking spray did the trick and I now have a nice clicky joint again. The ratcheting teeth came out surprisingly well defined. Awesome stuff! Highly recommended for making simple part molds and copies, would probably work great for sculpting as well if you had a heat gun to keep the outer layer pliable as you sculpt, as the only downside to this stuff is the relatively short working time - maybe 2-3 minutes. I've never made a mold before but it was pretty simple. I can think of about 100 uses for this stuff.