Invisible ink responds to LED light

Secret pen with UV light children - simply make invisible ink yourself

What is secret ink anyway?
- UV light, UV pen, black light pen or simply UV pen with lamp - there are many words for it, but they all describe the same thing: Magic pens UV light that cannot be seen and can only be made visible through additional measures. Hence the name.
- There are several different versions of the invisible pen, you can make them in different ways, I would like to introduce you to them here, all of which are made visible in the same way.
- Using UV pens for kids is fun and exciting. You can send secret messages to your friends and family using ingredients that are lying around the house. There are many different solutions that you can use as a UV light pen and even more ways to get the message across. Any slightly acidic liquid can be used as an invisible secret pen with UV light. With a little heat you can reveal all the secrets!

What can be used to make cryptographic pen?
* Lemon juice (probably the most famous version)
* Orange juice
* Apple juice
* Onion juice
* Vinegar
* Milk
* Ink eraser or ink killer
* Salt water
* Sugar water

This is how you make the giveaway pens:
- Before you start, make sure you have an adult with you. Making it visible is not entirely harmless, so don't do it alone.
- Ask your parents about the following things:
- A sheet of paper
- A fountain pen, a pipette or a normal nib (the fountain pen must be clean, i.e. no more ink, otherwise you can see the ink and it is no longer invisible)
- One of the liquids from above (lemon juice, apple juice, etc.)
- A floor lamp (with a lightbulb) or other heat source (lighter or stove top will also work if you are very careful)
- That's it, you don't need more. Now you can start writing.
- First clean the pen properly before you start. To do this, simply let water run through the opening that the cartridge normally goes into.
- Now take the fountain pen (or the pipette, the pen or something else), dip it in the juice and use it to write on the sheet of paper.
- Now just let the paper dry and that's it! As you can see now, you see nothing. The writing is invisible!
- In order to make them visible, you have to carefully heat the paper. This is relatively easy with a lightbulb, but also works with a lighter or the hotplate, for example. Definitely let your parents do this! Your parents must also be careful not to get burned in the process!

How does the invisible pen with UV lamp work?
In the case of lemon juice, the following happens: The acid contained in the lemon juice reacts with the paper and slowly attacks it. It is "thermally decomposed", which means that heat plays a major role. If you hold the sheet on something hot, like the stove, this process will be accelerated. The acid degrades the paper even faster and it turns brown.

You can easily make a UV secret pen, i.e. the UV color invisible, yourself. You should only consider beforehand whether you really need the quantities that you have to buy to make an invisible pen yourself on a permanent basis.
The homemade secret pens for children will definitely bring your children a lot of fun with the secret games about dragons, pirates and princesses.