The Invisible Ink
What is it actually?
Invisible ink is actually an ink which is much secured to be used in writings purposes. This is because the ink is invisible to our naked eyes. In addition to this, invisible ink is a type of steganography which means that it is the study of science and arts in writing messages invisibly. The word steganography comes from Greek word where it means protected or shielded.
How to use it? What are the main applications?
Mainly the invisible ink is made for writing purpose where the ink is invisible as soon as it dries. The ink is not visible in our naked eyes and the paper appears blank. However, in order to make the writings could be seen, the ink may be visible under ultraviolet light. As such, inks which are made by chemical reaction should depends on the acid-base reaction which most similarly with the blueprint process. For example, to make phenolphthalein indicator, ammonia fumes is used. Some of the applications may be seen in the printing process. Very rarely people will use the invisible ink to print documents or anything or sheet of papers. However, for the developer which named is Vermont PhotoInkjet, LLC which is under the market of Firefly brand, they used a non-toxic and fully colour invisible ink jet ink for their printers. This bizarre printer has been named by the Epson printer. You could find this type of printer at the market out there. This type of ink can only be seen under black light which is also well-known as ultraviolet light. How amazing is that, right.
There are also some properties of invisible light which are :
1. - non-greasy ( very water soluble)
2. - no smell and non-volatile
3. - not easily seen under glancing lights
4. - should not be developed under heat
The Disappearing Ink
There is also a type of ink where it is called as disappearing ink. This type of ink will be visible for a period of time without the intention to make it visible again. This ink practically based on the chemical reaction between thymolphthalein and a base substance. One of the common base substances used is sodium hydroxide. How this does happens? Usually, thymolphthalein is colourless which later then to react with sodium hydroxide ( a base) to form a blue solution. Thymolphthalein is an acid-base pH indicator with a pH of 9.3 to 10.5. In addition, if below this pH it will become colourless. However when it exceeds this pH, it will turn to blue.
How can it disappear again?
As the blue solution will always contaminated or exposed with the presence of carbon dioxide gas from the air, the pH of this solution will drop as below to 10.5 which makes the blue colour disappear. In which on other word means, it is invisible. This kind of ink also applicable to the type of pen which has an eraser on it. This type of pen has an ink which can be erased. The ink that has been used is the same as the disappearing ink. There is also another way to make the colourless thymolphthalein becomes blue. You could dissolve the thymolphthalein with an alcohol solution which will exceed the pH value. Then the solution will turns from colourless to blue.
The Ink Pen with Eraser (Disappearing Ink)
How to make invisible ink on our own?
You will need a baking soda, paper, water, light bulb (heat source), paintbrush and cotton swab, measuring cup and purple grape juice (ascorbic and citric acid)
Firstly, you need to mix the baking soda and water well. Later on, use a cotton swab or paintbrush to write a message or anything to draw with that mixture solution onto a white blank paper. This baking soda mixture indicates as the “invisible ink”. After that, let the paper dry. Now, in order to read the message, you should have a light bulb or ultraviolet light as at the heat source. The invisible ink can only be read when there is heat source which the most common is from the lights. Later on, the invisible baking soda will turn to brown. The alternative way of reading the invisible message is by painting over the purple grape juice so that the ink will appear in different colour.
There are some precautions that you should take in seriously,
· - The baking soda will actively react with the grape juice as in the acid-base reaction. The grape juice contains ascorbic and citric acid.
· - If you are using the heating method to read the invisible message, please ensure that you are not igniting the paper itself. In this matter, try to avoid using halogen bulb.
The baking soda ink
The Invisible Ink under UV light
