These Heat Sensitive Hypercolors really make their mark! Hypercolor Thinking Putty is thermochromic -- just a touch from your hands or a warm coffee mug will reveal a new "hot" color. Allow it to cool off or stick it in the fridge! Then the "cool" color will be restored. You can even do tricks with Hypercolor Thinking Putty! Each metal tin is hand packed with 90g of Thinking Putty, much more than you get in a plastic egg!