Lemon Spy Letter Secret Ink

What you need

• Clear cups, 1 small bowl
• Water, a few drops
• Cotton swabs, 4 to 6
• Paper, 2 sheets of white paper
• Milk, a splash, or apple juice (optional)
• Lemon, 1
• Knife, 1, for the grown-up
• Iron or lamp, 1, grown-up only
• Towel or newspaper, 1, to cover the table

How to do it

Grown-up prep: Set out the supplies on a protected table and decide where the grown-up will do the heating. Keep the iron or lamp well away from little hands until it is time.

1. Squeeze the lemon half into the small bowl.
2. Add a few drops of water and give it a stir.
3. Dip a cotton swab and write your secret message.
   Ask: Do you think your words will still show up once the paper dries?
4. Wait while the paper dries and the writing vanishes.
5. Try a second ink! Write with milk or apple juice.
6. A grown-up warms the paper to reveal the message. A grown-up does this
   Ask: What do you think will happen to the paper when it gets warm?
7. Watch the writing turn brown, then compare the inks.
8. Give your spy letter to someone at home to decode!
   Ask: Who will get your next secret message, and what will it say?

Play it again

• Treasure hunt: draw a secret map of your home and hide a treat at the X.
• Ink contest: test lemon, milk, and apple juice side by side and rank them from darkest to lightest.
• Spy mail: send a daily secret note to a family member who must reveal it.