Marker That Let's You Know Your Drink's Heat!
This marker from 'Ink N Drink' has color changing ink for coffee and tea cups to indicate when a drink is cooling. The ink writes dark blue but changes to bright green when a drink hotter than 150F enters. As drink cools, ink slowly fades to blue to indicate drink is cooling. When completely blue, drink is at 150F which is deemed a safe-for-the-tongue temperature.