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. Made in the USA! Just as an evening sky melts into the dark of night, Twilight Thinking Putty's deep purple color disappears with a touch of heat to reveal a fluorescent blue complexion.