The Paper Mate Replay Premium uses a thermosensitive ink which goes clear once heat is applied. The action of rubbing it out with the eraser handily situated on the cap, and the resulting heat created from the friction is enough to make the ink go clear – clever stuff. You can then re-write over the top of what's just been erased.

Thermosensitive ink pens are great for sending secret messages – write your message, erase it and leave a cryptic clue to the fact that only ice can reveal its secrets. The ink in the Replay will change from clear to colourful if it gets cold enough so anything you erase can be recovered with the help of a freezer.