Write your message with lemon juice, milk, or baking soda solution on plain paper
Let the paper dry completely so the writing becomes invisible
To reveal it, gently heat the paper with a lamp, iron, or warm surface
Keep the heat moving to avoid burning the paper
Use a cotton swab, toothpick, or small brush for neat writing
Test on scrap paper first to find the right amount of liquid
If using a UV-reactive ink, write the message and let it dry
Reveal UV ink with a blacklight or UV flashlight
Fold or seal the paper so the message stays hidden until opened
Use a clean sheet and avoid pressing too hard so the message stays concealed