When oxidation has occurred, it turns the paper brown, revealing the message.
Once the carbon comes into contact with the air, it goes through a process called oxidation. When you heat the paper, the heat causes some of the chemical bonds to break down, freeing the carbon.
When you paint the lemon juice solution onto the paper, the carbon-based compounds absorb into the paper’s fibers. Lemon juice is an organic substance, meaning that it contains carbon molecules. These invisible ink valentines were a huge hit! We opted not to try the hair dryer as the loud hot blasting air just seemed to take away from the magic of it all. The candle was notably quicker (it still takes a few minutes) but it was easy for my daughter to get relatively close and see the letters appear. We tried using a light bulb at first since it seemed safer than an open flame, but it took a really long time and the letters were really faint. You can also use a light bulb or hair dryer to reveal the hidden message. Don’t be tempted to rush the process by holding the card too close to the flame. The heat from the flame reveals the message and eventually enough heat will build up under the valentine. It’s best to take this part slow and be patient. If you accidentally light your heart on fire, you can simply toss it in the bowl to extinguish your burning heart. It’s a good idea to keep a bowl of water close by, too. Obviously, these invisible ink valentines require an adult’s help and you’ll want to keep the heart several inches from the flame. At first, my daughter was a little apprehensive about holding paper over a candle but, once she saw her message slowly appear, her face was all smiles. Once the lemon juice dried, it was time to reveal the magic.
Using heat and lemon juice to reveal hidden messages how to#
It took her several hearts to figure out how to fit her message without running out of space. It’s a good thing she loves cutting because she had a few dozen to cut out! I had her make several extra in case she made a mistake when writing with the invisible ink.Īfter squeezing a lemon to get its juice, my daughter dipped the Q-tip into the juice and wrote her secret messages on the hearts. It was a bit of a challenge at first as she figured out how to keep the pencil right along the side of the heart she was tracing. She traced heart shapes on pink, red and white cardstock. My 6 year-old, however, wanted to cut out heart shapes to make more classic-looking cards.
What kid doesn’t like a little bit of magic?! Add in a sweet message and you’ve got a sure fire winner for Valentine’s Day.