Made Secret Ink Experiment

Sometimes called security inks, invisible ink or secret ink are substances that can become invisible to the application to the surface, or shortly afterwards. This ink is often used by security and intelligence professionals, to hide messages intended for specific audiences who know how to disclose concealed shipments.

Made Secret Ink Experiment

Ink Invisible Type
Invisible ink can be divided into two categories, organic liquids and sympathetic ink. The forms of both categories use natural methods, such as lemon juice vinegar, milk, sweat, saliva, onion juice and even blood. Organic invisible inks can be developed by using heat from a fire, iron, light bulb or anything else that emits sufficient heat, thus causing a reaction with a substance.

Synthetic invisible ink, also known as sympathetic ink, is more complicated and requires some skilled chemistry to produce fluids. More than one chemical is often required to make certain ink and reagents necessary to develop a message, which often consists of other chemicals.


To write and visualize words with invisible ink.

Made Secret Ink Experiment

Steganography, espionage, Anti-counterfeiting, Marking properties, signature stamp for re-listing

Basic theory
Invisible ink is a substance used for writing, which is not visible during the making, or several hours after the making, and can then be made visible in several ways. After the paper is dried, or the surface of the written material will be empty and the texture will be the same as the surrounding material.

Made Secret Ink Experiment
Blue print is an example of an invisible ink

There are several types of invisible ink. Different types of chemicals can be used and displayed under heating conditions, ultraviolet (UV) light, fluorecence, and the addition of other acid-base solutions by mixing or spraying fumes, or other means. One notable example is the blueprint. Based on these principles, the ink-pen toys are invisible with two ends made, one tip for writing invisible ink, and the other for developing ink, or for generating a written password. This pen is now developed and sold in the market.

Made Secret Ink Experiment
Invisible ink with UV light

Although it seems to be difficult, invisible inks can be easily made at home by spraying ammonia smoke on paper written with phenolphthalein. Phenolphthalein is a chemical compound normally used in titration. Phenolphthalein is colorless in acidic and pink or even purple solutions in an alkaline solution depending on the concentration of the indicator. Ammonia is usually encountered as a gas and is very volatile. Ammonia acts as a base or a proton acceptor, although it is not colored in liquid form, when it interacts with phenolphthalein, the solution changes color to pink. At the time of spraying ammonia fumes into phenolphthalein, visible writing appears on paper. But when the ammonia smoke evaporates, the writing is invisible and disappears again.

Made Secret Ink Experiment
Invisible ink pen

Equipment and materials
1. Phenolphthalein solution
2. cotton or brush
3. White paper or tissue paper
4. Beaker glass
5. Ammonia (with sprayer)
6. Acetic acid or vinegar

Made Secret Ink Experiment
Phenolftalein Solution

The paper used in this experiment can be used many times after the first article has been lost. All the materials used in this experiment are very easy to obtain. Solutions of acetic acid and ammonia can be stored in suitable containers to prevent evaporation.

1. Cut a piece of paper, dip a cotton ball or a brush into a phenolphthalein solution and write a message or picture onto a piece of paper. Dry the paper in the open air.

2. Spray the paper with a spray containing ammonia and observe the word that appears on the paper and then disappears.

3. Repeat the same process with acetic acid, and the paper will look clean again

Does the writing work and disappear into paper after being sprayed with ammonia and acetic acid? If not, does spraying with more solutions help the words to appear? How long does it take for words to appear on paper?

Many are also compounds that can be used to produce invisible ink. For example, organic substances, including cola drinks, honey, lemon, milk, onion juice, soapy water, sugar can all be oxidized to a brown color when heated.

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