The uncle has been currado these coasters detectors temperature is a host as the top of a pine. Basically have a small solar panel wrapped in a resin water-proof. The cold drinks produced in him a blue light and a hot red light.

If you want a similar fabricarte, Amazon sells the Hungry Scientist in the Handbook, which is included for 12 dollars. If you lazy, you can still poking his finger at the glass as did until now, guarrete.