Review on Invisible Upgraded Message Goodies: Unveiling FLYOME's Novelty & Gag Toys! by Eric Grayson

That's great! They dry completely transparent. You can't tell there's anything on the page. And they show up beautifully on white paper with light. I used them for my son's birthday. I wrote clues with pens to tell him where to find all his gifts. They enjoyed using the pen light to read their clues and then started writing their own secret messages.