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How to make invisible ink?

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You can play with your kids at home making invisible ink with basic products that you have in the kitchen. There are many methods to make invisible ink. These are some of the easiest ones.

message

1) Lemon juice method

- Ingredients: just lemon juice.

Write your message on a piece of paper with a brush or tootpick embedded in lemon juice. Let it dry completely.
To read the message heat the paper for a while (for instance hold it close to a light bulb) until the words become visible. Warning: do not hold paper too close to the heat and be careful not to let it get too hot!

- Chemical explanation: Lemon juice is a mild acid that weakens the paper upon contact. So when you heat the paper the part with the juice burns before the rest making your message visible.

2) Baking soda method

- Ingredients: baking soda and water in same amount (for instance 30 mL of each).
Mix them and use a toothpick or brush to write on a piece of paper. Wait until it dries completely.
To read the message paint the paper with a brush or a sponge embedded in concentrated grape juice. The message should show up.

- Chemical explanation: You've made an acid-base reaction. The baking soda is a basic compound that reacts with the acid contained in the apple juice, forming a new compound that has a different colour, making your message become visible.

 

Silvia Martínez

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