EC loves anything that could be remotely spy related, so when I suggested that we write our Valentine’s cards in invisible ink, he jumped at the chance.

Before we go any further I will say that although writing the cards is fine, reading them requires ADULT SUPERVISION. To activate the ink you need to place the letter next to a heat source. I tried a light bulb and a hair dryer but they didn’t work for me. What really worked was holding the paper above a candle. As you can see, this could be a potential  fire hazard. So make sure that you either do this part outside or with water nearby. The first note I practiced on went up in flames.

Now that we have that out of the way, let’s get down to business.

You will need:

  • Card stock in black and red
  • Glue
  • Pencil
  • Scissors
  • White paper
  • ½ a lemon
  • Small bowl
  • Ear buds

To write the secret love note you will need to squeeze half a lemon into a small bowl and add a few drops of water.

Cut some plain white paper into small notes. I tried with a variety of different types and coloured paper but none of them worked.

Dip an ear bud into your lemon juice and use it to write, or draw, your love note.

Then leave it to dry.

While waiting for it to dry it’s time to make your cards.

First cut out a heart shape from the red card.

Then cut out a black square that is big enough to fit the heart in it.

Add a little bit of glue to the outside corners of the heart and stick it down. You don’t want to glue the top part of the heart down as this is going to make a pouch for the letter to sit it.

Once the letter has dried roll it up and place it into the pouch on the card.

I’ve never had to put one of these on a card before.

To complete it I put instructions and a warning on the back of the card, which is a first for a Valentine’s card.

To read the card/ Science behind it

The lemon juice is an organic substance that oxidises and turns brown when it comes into contact with heat. You can apparently do this with a hair dryer, light bulb or even an iron, but I didn’t have any luck with those. I used a candle. The trick is to get the paper close enough without actually touching the flame. I held it over for a few seconds at a time and then removed. It was pretty cool to watch the message suddenly appear like magic.

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About The Author

Nanny Anita
Norland Nanny

Nanny Anita is our resident Super Nanny. Having trained at the famous Norland College, in Bath, she has over 12 years experience, working all over the world with children from 2 months to 17 years old. Nanny Anita is an expert when it comes to keeping the little ones entertained and writes a column with Leonora called 'Get Crafty' for Little London magazine. Nanny Anita has been on hand to answer our reader questions, and she provides weekly arts, crafts and activities for families to do with their children at home. She really is a modern day Mary Poppins!

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