Official Elemental Ink Pens from The Shop of Many Things. Use it to create hidden messages for your D&D players to discover, or for use in a treasure hunt for your friends and family. The magic ink becomes completely invisible when exposed to heat. Direct flame works well but also a hot lightbulb, a hot mug of just boiled water or even an iron work too, if taking fire to paper isn't something you trust your players with! Make the Elemental Ink reappear by getting the message cold enough. Thirty seconds in the freezer works great, but dry ice or other arrangements work too if you want to take it to the next level! Elemental Ink Pens make a great addition to any Dungeon Master's toolkit. >>> FAQ >> What paper does it work on? It works on all types of paper! >> Isn't it going to light the paper on fire?! No! The Elemental Ink disappears at 104°F (40°C) whereas normal paper lights at 451°F (233°C). >> How cold does it need to get? The ink reappears at at around 14F (-10C) so freezer cold works well, but you could also use dry ice or something else.