What's the name of the product or material where something is apparently written, let's say it's the 6 of clubs, you then apply heat (fire or your hand) and then that 6 of clubs vanishes and there is something else written in its place like the queen of hearts? This can be any written word changing into another word.

Thanks,

Henok

You can try the Pilot FriXion Gel Ink Pen which is available in most good stationery suppliers such as Staples. This uses thermo-sensitive ink.