The Bar Convent exists because of a remarkable woman namedMary Ward. Four hundred years ago, she founded an order of nunsand created schools for girls all over Europe. Her sisters still live inour building today.

Though Mary Ward was a Catholic, she disagreed strongly withthe church about how nuns and other religious women should livetheir lives.

Mary wanted to go out in public and spread the word of God, while the church believedthat women like her should live safely behind convent walls. She challenged the church sooften that they eventually closed all her schools and put her into prison.

While in prison, Mary had to find a way to send secretmessages to her friends and supporters. She did it using aspecial kind of ink, which is invisible unless you know thesecret of how to read it.

That ink is lemon juice!

Twenty three of Mary Ward’s lemon juice letters still existtoday. She was eventually released from prison and wenton with her good work.

Read on to discover the secret of how towrite a lemon juice letter of your own...

You will need:

● An adult to help you with some steps● Lemon juice - either freshly squeezed or from a bottle● A plastic cup● A cotton swab● A sheet of plain white paper

Instructions

● Add a little bit of lemon juice to a plastic cup. You won’t need much - a couple oftablespoons will do.

● Carefully dip a cotton swab into the lemon juice.● On a piece of white paper, write out your secret message. Keep the letters nice and

big so they’re easy to read, and make sure to re-dip the cotton swab now and then.● The lemon juice will stay visible while it’s wet, so let the paper dry completely. This

will take a little time. As it dries, your message will vanish away into the paper...● To reveal your message again, you’ll need to warm up the paper. Make sure you

have an adult to help you with this step! We don’t want you to burn yourself.Here are some ways for your grown-up to heat the paper:

○ Holding the paper close to a light bulb○ Holding the paper against a warm radiator○ Ironing the paper (not on a steam setting)

● The paper will wrinkle as it gets warm… then your message will magically reappear!

Science time! How does it work?

Lemon juice is a weak acid. It softens up the fibres in the paper, leaving behindcarbon-based compounds as it dries. These compounds have no colour at roomtemperature.

When heated, the compounds in the dry lemon juice break down, releasing some of theircarbon. This carbon then oxidizes in contact with the air, turning the paper a darker colour!

We hope you had fun creating your lemon letter!Make sure to share a photo with us on Twitter, Facebook or Instagram: