Invisible Ink

Sympathetic ink is a solution for writing information on paper. They differ from ordinary inks in that the message written by them cannot be seen until certain conditions are applied, be it warm, light, or so on. This method of transmitting information has been one of the main elements of encryption at all times. As a rule, secret information was first written on a clean sheet of paper, and sympathetic ink was used. After drying, on top of the transparent lettering, the usual message was applied with simple visible ink. Such letters, as a rule, were heated, so that a secret code appeared, and then they destroyed the sheet. There are many all kinds of invisible ink recipes, including purely chemical inks, which are already sold today in the departments of stationery. However, such spy ink can be prepared independently. For this you will need: Regular baking soda, some warm water, a spoon,a toothpick with cotton (you can also use a cotton swab or a refill pen), a piece of paper and a candle.
 Invisible Ink
Step 1. Drink soda to dissolve in water so that The result was a concentrated solution. It is necessary to allow the mixture to cool slightly. It is not necessary to achieve complete dissolution of soda.
 Invisible Ink
Step 2. If there is a fountain pen that can be refilled with a freshly prepared solution.
Invisible Ink
We'll use it. If there is no such device at hand, you can use a cotton swab or a regular toothpick with a piece of cotton at the end.
 Invisible Ink
You need to dip it in an aqueous solution of soda, slightly squeeze. After that, you can safely write a message on a blank sheet of paper.
 Invisible Ink
Step 3. It is advisable to allow the ink to dry slightly before starting to develop the letter. In order for secret recording to become visible, a sheet with it must be held over heat.It can be an iron, gas or electric stove, but in our case a regular candle was used. To prevent the paper from catching fire, you need to lightly drive it over the flame.
 Invisible Ink
Step 4. If everything is done correctly, in about 30-40 seconds an inscription of a yellow-brownish tint will appear . Done! The inscription is shown. You can also heat a sheet with a secret recording on the battery, but it will take much longer and the recording itself will not be so bright.
Invisible Ink
You can also use instead of a soda solution, lemon juice or concentrated vinegar, but these substances leave slightly visible traces on the paper, which no longer corresponds to the “secret” stamp.