Read this aloud:
Long ago, spies needed to send messages that enemies couldn't read. They wrote on ordinary-looking paper with special inks that dried invisible. The person receiving the letter knew the secret: one special liquid would make the words appear. Your job: write a secret message only your partner can read, and find out how the trick works.
Jobs for one, two or three kids:
- Ink maker: stirs the ink and the reveal liquid.
- Spy: writes the secret message.
- Decoder: paints on the reveal liquid and reads the message.
With one child, they do all three, and the grown-up writes them a message too. With two or three, swap papers so each child decodes someone else's message.
In the full lesson PDF
- Bet (5 min)
- Hunt (20–30 min)
- Reveal (10 min)
- Act (10 min)
- The science, for grown-ups
- Questions they'll ask (and what to say)
- Make it easier, make it harder
- Go further
- Student sheet
Written for parents: no science background needed. US Letter, prints cleanly in black and white, with a kids’ sheet on its own page.