°C and it becomes soft like putty, but at room temperature it's hard like any other plastic. Sounds like you could use it to fix/build a lot of things. And the great thing is, it's reusable. So if you don't like what you made, just melt it again. It's actually polycaprolactone, a polyester. But does it live up to its name?
What's it like to work with? Well, even though it was just taken out of hot water, it's not that hot. It's easy to shape, although it springs back quite a bit. It sticks to some things, including itself, but not your hands or polished 3D printed nylon (hmm), making it easier to work with than modelling clay. One problem is the hot water kept cooling down, so it's much easier to work with this if you have a heat source.
I made an iPhone dock:
The rear view reminds me of ankles. It's not visible here, but the vertical arts are narrow, like ankles viewed from the back.
Link to all posts on Instamorph: http://mbni.blogspot.sg/2013/04/instamorph-contents-post.html