How does this work? color changing material

[George]

Someone had one of these in Science class today. Everyone was interested so the teacher assigned extra credit for anyone who could tell her how it works. Has anyone seen this technology before? The only link I could find is below. Thanks!

 

http://www.youtube.com/watch?v=5hamvMFwKgo

[Klaynos]

The clue is in 'hot'

[George]

Hi. We figured out it was heat. But couldn't figure out why the color went away with heat. The ink or paint became invisible when we touched it. I think she's looking for something scientific like some kind of reaction is happening.

[swansont]

Mood books now, instead of mood rings?

 

Think phase change when they are heated past a certain temperature, and so their reflective/absorptive properties change. What kind of material might do that?

[George]

I think that is it. I think that when the ink heats up it changes its composition and becomes clear. What I found on mood rings is the same idea but works the opposite way. The mood rings make colors when they are heated. Thank you.

[swansont]

Google/wiki on thermochromic pigment for more, and send my share of the extra credit to me.