Question-answer No. 20
Added: 12/05/2013

From time immemorial, almost immediately after the appearance of writing, people began to think about the possibilities of keeping the secrecy of correspondence. Of course the best remedy invisible ink has become to solve such problems. Cryptography, applied to paper with the help of special substances, made it possible to hide the mass various secrets... A meaningless record, visible to others and applied over the disappeared words, carefully kept its secret until a "craftsman" was announced who could read the text hidden between the lines.

Today, invisible ink, also called sympathetic ink, can be made on your own at home. This unique invention can be used for various purposes, but in most cases, it is the basis of all kinds of comic pranks. For maximum masking of records with invisible ink, in order to hide the slightest hint of their presence, you can write something else on top of such a colorless text, for example, a poem by Pushkin.

There are several recipes for making sympathetic ink:

The first way

In the old days, liquids were used as disappearing ink, which, after drying, did not leave the slightest trace on the paper: white wine, beer, milk. To develop a recording made from the above "ink", you need ordinary ash. To enhance the effect, the paper can be slightly breathed before being treated with ash.

Second way

Quite good results can be achieved using rutabaga juice, apple juice, onion juice, citric acid. For the manifestation of messages written in such invisible ink, it is enough to hold a sheet of paper at a distance of ten centimeters from the fire. If you do not want to come into contact with fire, you can simply hold the paper under a hot iron.

The third way

Starch can also be used to make invisible ink. To read the inscription, the paper should be treated with a weak iodine solution. As you know, under the influence of iodine, starch turns blue.

Fourth way

Regular laundry detergent can also be a good base for creating colorless ink. To read the inscription, it is enough to place it under an ultraviolet radiation source. As a rule, such lamps are used in nightclubs, tanning salons, devices designed to detect counterfeit banknotes.

Fifth way

Often, in extreme conditions, ordinary saliva played the role of ink. A weak ink solution was used for development.

Sixth way

If you inject a small amount of a colorless phenolphthalein indicator into a quill with a syringe, you get a good improvised pen. To show the record made by her, you need to use a swab soaked in any alkali (sodium hydroxide or potassium hydroxide). The letters will instantly take on a crimson color.

Seventh way

You can write colorless messages with rice water. To develop the recording, it is enough to treat it with a weak alcoholic solution of iodine. As a result, the letters turn blue due to the starch in the rice.

Eighth way

You can make notes on paper from a highly concentrated solution of cobalt chloride. Such a text appears beautiful in blue when heated. Moreover, later such a record can be "made" to disappear again. To do this, just breathe on it or hold it over the steam.

Ninth way

Dextrin and iodine will also help create disappearing ink. Dextrin is a substance obtained by heating starch. 3 grams of dextrin are added to 30 ml of iodine and passed through filter paper. With the resulting blue ink, they write some text. After a couple of days, the record will disappear without a trace, and it will be impossible to restore it, due to the volatility of iodine.

Cryptography is good and interesting, but maybe it is worth moving away from cryptography and turning to steganography, that is, to hide the fact of the message by writing it in invisible ink?

It's already here, but let's put together a longer list ...

Flaw invisible ink in that they were mentioned by Ovid and Philo of Alexandria. That is, it is enough to check the correspondence once to find the message. The same incident with Lenin and milk described here was known to the tsarist secret police and Lenin's correspondence was successfully read by the enemy.

However, invisible ink has been used and used for many centuries, it was popular not only in the Middle Ages, but also in the First World War and even, sometimes, in the Second, despite the spread of radio. Actually, they are still used, but already in other areas - for example, they mark banknotes to identify a bribe-taker.

So, let's take a look at invisible ink by developing methods:

Heat Developing Ink
This is the oldest and most primitive method. Only a lazy spy from pre-Khrst times did not know about him.
However, there is a twist in it - if the enemy read the letter, then it will definitely not reach, and what has reached is unread. I think Lenin used this very property when he sent letters with milk.
Here you can use:

1. Honey or sugar (caramelized at temperature darkens).
2. Lemon, apple, onion (organic acids react with paper when heated).
3. Milk (lactose dehydration).
4. Blood serum.
5. Soap (carboxylates are oxidized).
6. Vinegar.

Here, apart, you can add the paragraph 7 , cobalt chloride.
The fact is that in the first six paragraphs the inscription appears irreversibly and it is impossible to deliver a letter in this form to the addressee - it is clear that it has been read. Cobalt chloride, when heated, becomes of blue color, and when it cools down, the color disappears. Sure, it's nice to add it to the paint to an enamel teapot to see if it's cold, but for cryptography ...

Developing ink with chemicals
Here we will try not to mention ink that reacts to heat.

1. Phenolphthalein, the most famous acid-base indicator. Accordingly, it is necessary to show letters with substances to which he reacts. The easiest way is to take soda or potash with an alkaline reaction.
It is quite a hit-and-miss option, because phenolphthalein is obtained from phenol, which the victim will still have to extract in order to get it for carbolic acid.
The disadvantage is that both acids and alkalis are too simple substances that the enemy will have available.

2. Ammonia, that is, ammonia. It is manifested by a ph indicator made from red cabbage (the technology is primitive, google "red cabbage water").
The method ... let's just say it's bad.
Ammonia was expensive in ancient times, and the presence of cryptography is easily determined by smell, which is not at all in any gate.

3. Copper sulfate. It occurs naturally in the form of the chalconite mineral. Manifested by sodium iodide, sodium carbonate, ammonia hydrate or red blood salt.
Quite a viable option. The main thing is the secrecy of obtaining chemicals for development.

4. Lead nitrate. The compound has been in use since the 16th century. It is manifested by sodium iodide. For ancient times, the level of secrecy is very high.

5. Ferrous sulfate. Manifested by sodium carbonate or red blood salt. An ancient method.

6. Starch. It manifests itself in iodine compounds. A very interesting method, probably the most interesting. Starch is available, in fact, at all times. And it is still very desirable for a hitman to receive, for and not only.

7. Salt. It is manifested by silver nitrate ("hellish stone", "lapis"). Something tells me that in the Middle Ages this method was very well known.

8. Cerium salt of oxalic acid. It is manifested by manganese vitriol or hydrogen peroxide. For a hitman, he has a purely academic interest.

UV development of ink
Here the question is not in the substances with which they write, here the question is in ultraviolet radiation. Now there is a detector at any checkout in a supermarket, but for a stranger such it is more difficult to build.
But let's estimate the substances:

1. Fluids from the human body - saliva, blood plasma. Well, for aesthetes - sperm (I just have a bad idea how to write to her, even with a pen). Nevertheless, the substances are extremely accessible, there seems to be no need to continue.

2. Soap, lemon juice. But this is hardly suitable, because it is determined by heating. Blocking the ultraviolet detector in this case is stupid.

3. Sunscreen

4. Washing powder which contains bleaches.

Separately, there are several methods used in the First World War.

1. Taken raw egg, messages are written on its shell with vinegar. If the egg is boiled and peeled, the letters can be seen on the surface of the boiled egg. The method is very niche - it works over short distances and is hardly suitable for the Middle Ages. Well, maybe so - to convey the news from the besieged castle (although this may turn out to be a lot).

2. A bunch of all sorts of methods with photographic paper, where a developer is banal in a dark room, and the letter is in black opaque paper. There are so many variations of this method that it is necessary to describe separately. But does the hitman need it?

In the First and Second World War in the United States and Britain, all suspicious letters were illuminated with ultraviolet and infrared rays, processed with iodine vapor and ammonia vapor. The Americans caught a German saboteur in 1918.

Therefore, here's a snack for you - the requirements for perfect invisible ink formulated by British intelligence in the First World War:

1. Miscible with water.
2. They do not have a pronounced odor.
3. Does not form crystals on paper, otherwise they can be seen in reflected light.
4. Invisible in ultraviolet light.
5. Does not decompose or discolor paper (such as silver nitrate)
6. Does not react to iodine or any common developer.
7. There should be as few potential ink developers as possible.
8. Ink should not react to heat.
9. Must be readily available and have at least one plausible innocent use in the home.
10. Not be a compound of several substances.

It is easy to see that clauses 7 and 10, as well as clauses 6 and 9, are incompatible.
Nevertheless, the last time the use of invisible ink was noted was in 2008, when they found a notebook where al-Qaeda phones were written in invisible ink.

Invisible ink - The best way masking important text. Some people still remember how, under the Soviet Union, Lenin managed to transmit important statements from prison to his comrades-in-arms, on the sheets of an ordinary fiction book. Making invisible ink is as easy as shelling pears, let's get started!

How to make invisible ink with your own hands?

And so, let's prepare the things we need:

Milk or lemon juice;

Bread, black;

Fountain pen (or paint brush);

1. We will use the black bread to make the inkwell. We take a piece of bread and cut out a small container from it, about 50 milliliters.

If you don't want to use bread, you can use any other container. Bread is used to give this process a historical character, and completely immerse yourself in that atmosphere.

2. Pour milk into the finished inkwell.

The ink is ready!

How to use invisible ink?

We take a sheet of paper, dip the pen in ink and write on a sheet of paper. Soon the milk will dry out - the paper will turn white again. You can pour liquid into a syringe for convenience.

How can I read invisible text?

Instead of milk, you can use lemon juice, the effect will be the same.

How to make invisible ink from potatoes?

This time, we will use completely different ingredients, we need:

Potatoes, 1pc .;

And, of course, a sheet of paper, a pen and a candle.

Let's get started!

1. We take a potato and cut out an inkwell from it. We don’t throw away the leftovers!

2. Rub the cuttings on a grater and place them in cheesecloth. Then we squeeze all the juice into our inkwell.

Primary school project. Spy (sympathetic) ink

Brief abstract of the research paper
Learning the secrets of cryptography is a fun process. In this work, the author describes what invisible ink is, the history of its origin; an attempt was made to prepare several types of sympathetic ink at home and use them to write invisible text. The hypothesis that if "spy" ink is made in secret laboratories that develop special means for spies, then some of them can be made at home, was fully confirmed during experiments.
This work will be of interest to everyone who loves various secrets.
Table of contents
Introduction 3
Chapter 1. Theoretical study of the problem 4
1.1. What is invisible ink 4
1.2. The History of Invisible Ink 4
1.3. Sympathetic ink types: 5
1.4. Home technology invisible ink 6
Chapter 2. Practical investigation of the problem 7
2.1. Questioning classmates on the research topic 7
2.2. Writing tools and aids 7
2.3. Testing invisible ink 8
Conclusion 9
List of sources of information 10
Appendix 11

List of sources of information
1. References
1.1. Aleksinsky V.N. Amusing experiments in chemistry. - M .: Education, 1995 - 96p.
1.2. Lavrova S.A. Riddles and secrets of ordinary things. - M .: White city, 2006 - 48p.
1.3. Lavrova S.A. My first book. Entertaining chemistry for kids. - M .: White city, 2009 - 128p.
1.4. What? What for? Why? Big book of questions and answers / Per. K. Mishina, A. Zykova. - M .: Eksmo, 2007 - 512s.
2. Other sources of information
2.1. Invisible ink. Disappearing ink. [Electronic resource].
2.2. Do it yourself, do it yourself. Invisible ink. [Electronic resource].
2.3. Sympathetic (invisible) ink. [Electronic resource].
2.4. How to make invisible ink? [Electronic resource].
2.5. Who Invented Ink? [Electronic resource].
2.6. What is sympathetic ink for? [Electronic resource].
2.7. Children's lessons. How to make invisible ink. [Electronic resource].

Application
Annex 1
Classmates survey results
Have you watched spy movies?
Do you know about invisible ink?
What can you make invisible ink from?
Would you like to learn how to prepare invisible and disappearing ink?
What invisible ink can be made from
Appendix 2
Homemade Sympathetic Ink Recipes
Invisible ink from lemon - squeeze out the juice of half a lemon and dilute it with the same amount of water, manifest with heat;
Onion Invisible Ink - Prepare onion juice and use it as ink, exert heat exposure;
Invisible ink from milk - take milk and use it as ink, dry it, develop over a candle or lamp;
Invisible ink from baking soda - prepare concentrated baking soda solution - 1 teaspoon per 10 ml. - 2 - 3 teaspoons of water, move everything, use as ink, which persists for a long time, show exposure to heat.
Invisible ink from starch - prepare a solution of starch with water, move everything and cook until a homogeneous mass is formed, use it as ink that lasts a long time, develop it with an iodine solution (1:10).
Appendix 3
Experiment 1: Making Invisible Lemon Ink
For this we need: half a lemon, a glass, a brush, White list paper. Squeeze lemon juice into a glass, add the same amount of water. Dip the brush in a solution of lemon juice and water and write something down on paper. After the inscription is made, it must be allowed to dry. To develop the inscription, you need to heat a piece of paper, for example, iron it with a hot iron. Lemon acid darkens when exposed to temperature and thus my ink becomes visible.
Experiment 2: Making invisible ink from onions
For the experiment, we need the same as for the previous one.
Take half an onion, grate it on a fine grater and squeeze the juice through a piece of gauze into a glass. Apply the onion juice with a brush to the paper, wait until it dries. When dry, the juice of the onion is slightly visible on the paper, and has an unpleasant odor, which makes this ink imperfect. We will develop in the same way - by heating. Onion juice darkens when exposed to heat, and the ink becomes visible and takes on a brown tint.
Experiment 3: Making invisible ink from milk
Pour milk into a glass. Dip the brush in milk and write on a piece of white paper. Let the milk dry. There will be no trace or smell of the letters. We will develop in the same way - by heating, since milk will change color when heated. The milk really changed color.
Experiment 4: Making invisible ink from soda
It is necessary to prepare a saturated solution of ordinary baking soda in water. Dip a brush in a baking soda solution and write on a piece of white paper. Immediately behind the brush, the water evaporates, and there seems to be nothing on the sheet of paper. The secret letter also manifests itself very simply: by the influence of heat. When heated with an iron, dark brown text appears. Moreover, this text turned out to be the brightest and most uniform of all the previous ones.
Experiment 5: Making invisible ink from starch
Starch can also be used to make invisible ink. It is necessary to prepare a saturated solution of starch in water. I used a brush, as in the previous recipes. To read the inscription, the paper should be treated with a weak iodine solution. As you know, under the influence of iodine, starch turns blue.

How to make invisible ink? For this there is whole line ways. With the most popular, available options let's get acquainted in the presented material.

What is invisible ink

Invisible, or sympathetic, inks are specific solutions that are used to covertly display information on plain paper. For the inscriptions to appear, the use of a catalyst is required, be it chemical substances, warmth, light, etc.

This method of transferring secret data was very popular in the last century. As a rule, a secret message was written on ordinary white paper in sympathetic ink. Then, on top of an ordinary pen, an ordinary one was applied, visible text arbitrary content. Such letters were usually heated, studied a secret code, and then sent the paper to the fire.

Today, ultraviolet light, or rather, fluorescent paints, which are used to create watermarks, can be made invisible. Such substances make it possible to carry out high quality printing on banknotes, documents, forms of strict reporting. Under normal conditions, fluorescent dyes are invisible. They appear only under the influence of ultraviolet radiation.

There are a whole host of options for preparing fairly effective solutions for creating secret inscriptions. Some common ways to make invisible ink are discussed below.

Invisible Lemon Juice Ink

How to make invisible ink at home from lemon juice? To do this, squeeze the liquid from the half of the fruit into a container, add a few drops of water and mix the resulting composition well. Then you should soak a cotton swab in the solution and write a message on paper with it. In conclusion, it remains to dry the secret letter.

Lemon juice is, in fact, a fairly concentrated acid. Substances of a similar nature change the shade to a darker shade in case of exposure high temperature... In order for the text written with lemon juice to appear, you need to lightly iron the paper with an iron or hold it over a candle.

How to make invisible ink from copper sulfate

Copper sulfate, dissolved in water, gives a substance of a pale blue, barely noticeable shade. Therefore, the presented substance is excellent for creating invisible messages.

How to make invisible ink using copper sulfate? To do this, it is necessary to dissolve a small amount of a powdery substance in plain water... Then, using the same cotton swab or a match, you can start applying the message to the paper.

How to reveal information from a secret letter? In order for the written to become visible to the eye, it is necessary for some time to hold the paper over a container filled with ammonia... The couples of the latter will enter into chemical reaction with copper sulfate... The result will be the appearance of distinct, bright blue letters on the paper.

How to make rice water ink

Rice broth contains a significant concentration of starch, which, after drying on paper, does not leave clearly visible traces. To manifest a message written with a liquid made from rice water, it is enough to moisten the paper with a non-concentrated iodine solution. The result will be a distinct blue tint.

Invisible baking soda ink

How to make invisible ink from baking soda? The presented substance must be diluted in water so that the result is a sufficiently saturated solution. Then you can start creating a message. You can use any handy item to write on paper.

Let the invisible ink dry thoroughly before developing the letter. For the secret inscriptions to be visible, the paper must be exposed to heat. Here you can use a hot iron, hold the sheet over gas stove or a candle. After about a minute, previously invisible inscriptions will begin to appear, which will have a brownish tint.

Milk invisible ink

This method is one of the simplest and most affordable. To create secret messages, you just need to dip a cotton swab in milk and write on paper. Then it is enough to let the sheet dry and smooth it on a hard surface.

To show information, you need to hold the letter under an electric light. Since milk is heated much more slowly compared to paper, this will allow the hidden message to emerge.

Finally

So we found out which available ways exist for making invisible ink at home. Use any of the above solutions to play spy with your own child or exchange secret letters with friends.