Thermochromic Ink / Pigment - Science Experiment you can do at home
Pen can be purchased here: https://amzn.to/2IaYIBo
This is a Pilot Frixion Pen – you can erase the writing by using the other end of the pen. The ink used is thermochromic and goes colourless (invisible) when it gets warm. By rubbing the ink, you are creating friction (hence Frixion) and the ink vanishes. In this experiment I heat the ink up with a Bunsen which causes it to vanish. It can be made visible by cooling the paper down.