Add about 1 tablespoon (15 ml) of lemon juice to the cup. Fresh squeezed or bottled juice will work just fine.

Soak an end of the cotton swab or put the paint brush into the lemon juice. You’ll use this to write your message.

Write your message on the plain paper. You’ll be able to see it as long as the paper is wet so let the lemon-juice message dry completely.

There’s no rush to revealing the message but when it comes time to read it, there are several methods of heat sources. NOTE: If you choose the open flame method, make sure an adult helps out. Setting the message and/or yourself on fire are not what you want to do. Whichever method you choose, start at the bottom of the message and work your way up since heat rises.