How to Make an Invisible Ink Pen
Invisible ink is fun and exciting to use. You can send secret messages to your friends and family using ingredients that can be found lying around the house. There are many different solutions that you can use as ink and even more options for how to reveal the message. Any liquid that is slightly acidic can be used as invisible ink. With a little bit of heat, you can reveal all of the secrets!
Gather the necessary materials.
To make an invisible ink pen, you will need Q-tips or a paintbrush, an acidic solution, a shallow dish or bowl, white paper, and a source of heat. The Q-tips or paintbrush will be used to do the actual writing. Choose the item that works the best for you.
Any of the following can serve as the acidic solution for the invisible ink: milk, vinegar, or lemon juice.
The heat source can be a candle, a hair dryer, an iron, or even a lamp.
All of these items should easily be found around the home or purchased at the grocery store.
Pour the acidic solution into a bowl.
If you are using a lemon, squeeze the lemon until the juice comes out into the bowl. If you are using milk or vinegar, pour about half of a cup into the bowl. The exact amount isn’t important. You will only need enough to write your message.
Dispose of the liquid down the drain when you are finished.
Do not use the liquid for anything else once you have used it for invisible ink.
Write on the paper.
A Q-tip is a very easy device to use as a pen. Dip it in the solution until it is damp. Write your secret message, dipping the Q-tip into the ink every few letters. This ensures that you have used enough ink for the message to show up later.
It may be difficult to keep track of what you are writing because the writing will be invisible as well. If you write at a well-lit table you will be better able to see what you are writing while the ink is still wet.
Let the ink dry fully.
Before revealing your hidden message, you need to let the ink dry completely. It shouldn’t take more than 30 minutes for the ink to finish drying.
Set the first paper aside and write more messages while you wait for the first one to dry.
Apply heat to the paper.
Once you have obtained a heating device, apply it to the paper where something has been written with the invisible ink. As the paper heats up, the areas that have invisible ink on them will begin to turn brown. When the message starts to appear, remove the heat source from the paper. If the message is unclear, keep the heat on for a few more seconds until it comes clear.
Be extremely cautious not to light the paper on fire if you are using a candle. Adult supervision is recommended for this to avoid burns or other injury.
If you are using a hair dryer, use the low heat seating and wave it across the paper until the words appear.
If you are using an iron, use it on a low setting. To avoid burning the paper away, place a piece of parchment paper between the iron and the paper before rubbing the iron on top.
Reveal the writing with salt.
You can tweak this method a little bit by using salt instead of heat to reveal the message. When the ink is still wet, cover it in salt. Let the salt sit for at least two minutes and then brush it away from the ink. Let the ink fully dry and then color over the message with a wax crayon.
The wax will not stick to the salt in the ink and you will be able to read what is written!
There is no exact amount of salt to use, just make sure the message is covered completely while the ink is still wet.