I baked sidewalk chalk yesterday.
See, it had gotten left in an open ziploc bag in an open rubbermaid container out in the rain. All the safety features were there, they just weren't engaged.
So when I discovered our soaking wet sidewalk chalk, I was a little annoyed. Annoyed enough not to just go spend the $2-5 for more. I dried it with a rag, brought it inside and baked it.
To bake sidewalk chalk:
Line baking pan with foil.
Spread chalk evenly over pan.
Put pan in cold oven.
Set oven to lowest temperature possible. Mine will only go as low as 170 degrees.
Once oven has preheated, let chalk bake for about 30 minutes.
Turn off oven, but leave chalk inside (don't open the door!) until the oven completely cools.
The chalk is dry. It doesn't feel as dry as brand new chalk, but it is no longer squishable, and doesn't cover your hands in goo.
I'm sure my brother will be disappointed to read that our oven did not explode, we were not covered in flakes of sidewalk chalk, and I don't get to remodel my kitchen (honestly, I'm a bit disappointed about the last one).