Invisible Ink

A simple way to hide a message is to write it in invisible ink. For a few dollars you can get a pen that writes in ink that is hard to see but reacts to ultraviolet (UV) light.

The other part you will need for this puzzle is a UV light, also known as a black light.

The black light is given to the players, and the players have to shine it on the correct object. Words written on objects will be invisible until players reveal it with the black light.

Invisible ink pens are sold with different colors. I recommend using “yellow” invisible ink pens. Other colors I tried were slightly visible under normal light, which made them unusable for the puzzle.

You may have to experiment a bit on what you can write on. For example, I find I cannot write on a printed image because the pen will smear the printer’s ink just enough to see it. Different types of paper may work better than others. That said, give the ink a little time to dry before deciding it is too visible.