Some substances contained in milk or lemon juice are destroyed by heat faster than the paper itself catches fire.

During this chemical process, combustion products are released. Using this knowledge you can make invisible ink for secret messages.

Invisible ink
You will need:

White paper, brushes, pens or pipette, milk or lemon juice. (We even succeeded with apple juice). Candle for deciphering letters.:

• How to conduct an experiment
• Pour a little milk or lemon juice into the cups. Take a white sheet of paper and a pipette (or brush). Take some juice or milk into a pipette and write something on paper.
• Then let the paper dry thoroughly. The inscription disappeared and became invisible.
  Now place the candle in the center of the plate and light it. Take a dry piece of paper and hold it over the flame

candles at a distance of at least 10 cm. Constantly move the sheet back and forth so that it does not have time to catch fire.

In a few seconds, you will see the brown letters and drawings that you wrote or drew appear on the white paper. Sympathetic (invisible) ink - this is ink whose writing is initially invisible and becomes visible only under certain conditions (heating, lighting, chemical developer, etc.)

Wikipedia.

• Ink for secret correspondence, that is, sympathetic, was used in ancient times:
• Secret agents of Ivan the Terrible wrote their reports with onion juice. The letters became visible when the paper was heated.

Lenin used lemon juice or milk for secret writing. To develop the letter in these cases, it is enough to iron the paper with a hot iron or hold it over the fire for several minutes.

Using invisible (cute) ink is not only an integral part of children's spy games, but also an original way to surprise friends at a party or propose to your girlfriend. It is very easy to prepare them at home, and they contain the most common ingredients that are found in any home.

There are several types of sympathetic ink; they are distinguished not only by their composition, but also by the conditions under which the ink becomes visible.

Invisible ink at home using lemon

The recipe for invisible ink made from citric acid is one of the simplest and easiest to prepare. All you need is half a lemon or liquid citric acid, water, a deep plate, a brush and a sheet of white paper.

• First you need to squeeze the juice from the lemon into a deep plate and add a small amount of water. In principle, it is not necessary to dilute the lemon juice, but then the ink will initially be slightly visible on the paper.
• Mix the contents of the dishes.
• Wet the brush with the resulting liquid and write your message on white paper.
• Wait until the liquid is completely dry.
• When the time comes to read the message, the piece of paper must be heated. A table lamp, iron, candle or oven is suitable for this.

Due to the fact that lemon juice has the ability to oxidize when heated, it will change color to brown. Ink prepared without lemon, but, for example, from onion juice or honey, will work on the same principle.

Invisible ink from soda

There are several options for making invisible ink from soda, but all of them are simple to implement.

For the first recipe you will need baking soda, warm water, a piece of paper and a cotton swab or brush.

• Mix baking soda and water in a 1:1 ratio.
• Stir until the soda dissolves.
• Soak a cotton swab in the resulting liquid and write a secret message on the paper.
• Wait until the inscription is completely dry.
• To demonstrate your message, you need to heat the piece of paper using a lamp or any other method. However, do not forget about safety precautions when working with heating elements so that the paper does not ignite. You should prepare a container with plain water in advance to extinguish the burning paper if the process does not go according to plan.

The second type of invisible ink recipe using soda involves using grape juice to reveal the code. After applying the ink to the paper and drying it, you do not need to heat the sheet of paper to develop the message. Simply dip a brush or cotton swab in grape juice and paint the paper until the symbols appear. This occurs due to the chemical reaction of soda and grape juice.

Invisible ink made from milk

An incredibly easy way to make invisible ink. The ingredients you will need are milk, a sheet of paper and a brush.

• Write a message on a piece of paper with a brush dipped in milk.
• Wait until the inscription dries thoroughly.
• To manifest the message, just gently heat a sheet of paper.

Invisible ink from washing powder

For this recipe, prepare a small amount of washing powder, water, a sheet of paper, a brush, a deep plate and an ultraviolet lamp.

• Mix the powder with water and stir.
• Write an encrypted message on a piece of paper with a brush soaked in the solution.
• Let dry.
• To view the inscription, you need to turn off the light and bring an ultraviolet flashlight or lamp to the paper. The symbols will glow in the dark.

Invisible ink at home from starch

Ingredients for cooking:

Starch,

A small saucepan or ladle,

brush,

Paper,

Aqueous solution of iodine.

1) First you need to cook a starch paste. To do this, mix 2 parts starch and 1 part water in a ladle or saucepan. The resulting mass must be simmered over low heat until it warms up, while stirring thoroughly.

2) Allow the paste to cool.

3) Dip the brush into the resulting ink and write in large characters on a sheet of paper.

4) Let dry.

5) To read the message, you need to paint the paper with an aqueous solution of iodine. The inscription will turn bright purple.

Knowing the principle of interaction between starch and iodine, this recipe can be slightly modified if you do not have pure starch at home. It is enough to cook thick rice porridge instead of paste, since rice contains a large amount of starch. Further steps do not differ from those described in the recipe with pure starch.

There are also ready-made kits for preparing ink on sale, as well as various pens filled with already prepared sympathetic ink. However, preparing them yourself using simple and affordable ingredients will be much more fun not only for a child, but also for an adult.

Video on the topic of the article

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Introduction.

For the New Year, I was given a “Large Chemical Laboratory” set; it came with instructions, which described all the experiments that can be carried out. I was interested in one of the experiments on making invisible ink using the substance phenolphthalein and ammonia.

And I wondered, what other invisible ink exists, what are they made of, where did they come from, who invented them?

And of course, the greatest interest was raised by the question: can I, on my own, make such invisible ink at home?

Hypothesis: Let's assume that invisible ink exists and can be made at home.

Target: conduct experiments on making invisible ink.

Tasks:

Explore the history of invisible ink.

Find out what invisible ink is and how to make it.

Prepare the necessary equipment, equipment, and materials for making invisible ink.

Test your hypothesis about the possibility of making invisible ink yourself at home.

Analyze results

What is invisible ink and where did it come from?

Invisible ink is ink whose writing is initially invisible and becomes visible only under certain conditions (heating, lighting, chemical developer, ultraviolet or infrared rays, etc., etc.). They are also called sympathetic ink.

Since ancient times, invisible ink has been used to keep correspondence secret. The first invisible ink arose in ancient times.

The first recipe for invisible ink belongs to the Roman poet Ovid, he proposed using milk as invisible ink (appears after heating).

The Chinese emperor Qing Shi Huang, during whose reign the Great Wall of China appeared, used thick rice water for his secret letters, which, after drying, leaves no visible traces. But if the letter is moistened with a weak alcohol solution of iodine, then blue letters appear. And the emperor used a brown decoction of seaweed, apparently containing iodine, to develop writing.

The ancient Greek philosopher Philo of Alexandria described a recipe for sympathetic ink from the juice of ink nuts. In his case, the letters appeared after the writing was exposed to a solution of iron-copper salt.

In the Middle Ages, secret agents of Ivan the Terrible used onion juice to write their denunciations, and Vladimir Lenin also used lemon juice or milk for letters. To develop the ink, it was necessary to hold the letter over fire.

In later times, chemical inks became widespread. They were widely used by spies, intelligence agencies, and underground fighters.

Today, there is a special ink that only appears under ultraviolet light, which is used in the production of paper money.

Types of invisible ink.

Invisible ink appears under certain conditions and depending on the nature of the interaction of substances, all inks can be divided into the following types:

Chemical;

Photosensitive;

Luminescent;

Heat sensitive;

Moisture sensitive.

Chemical:

The composition of such ink includes substances that are colorless or weakly colored, which then, when interacting with other substances, acquire a bright color.

The chemical ink solution is applied to the paper and allowed to dry. The paper is then moistened with a developer substance and the “invisible” ink appears.

Photosensitive:

This ink appears or disappears when exposed to light. They can be divided into two groups.

The first group is ink that appears when illuminated. The second group is ink that disappears when illuminated and appears in the dark.

Photosensitive ink is applied to paper and air dried. The inscription is developed or removed by illuminating it with bright light.

Luminescent:

These inks contain colorless or slightly colored substances that can luminesce (glow) under the influence of ultraviolet radiation.

Luminescent ink is applied to paper. The paper is then illuminated with an ultraviolet lamp and the invisible ink begins to glow. After the ultraviolet radiation stops, the inscription disappears.

Heat sensitive:

These inks contain substances that exhibit color when exposed to heat.

The ink is applied to the paper and dried, at which point the inscriptions remain invisible. But as soon as the paper is heated with an iron, held over a fire or other heat source, the ink “appears.”

Such inks include lemon juice, onion juice, and milk. When heated, they most often turn brown.

The easiest way is to make and use heat-sensitive ink at home.

Moisture sensitive:

The writing produced by this ink becomes visible when exposed to water or steam.

Moisture-sensitive inks can be divided into two groups:

Translucent ink: after drying, the inscriptions are absolutely invisible on the paper, but if you hold the paper in water, the inscriptions become translucent. When they dry out, they disappear again.

Adhesive ink: inscriptions made with such ink appear when processed with steam and some colored powder. First, the paper with the inscription must be steamed, this will make the ink sticky. Then very fine colored powder is sprinkled onto the paper, and the remaining powder is shaken off. Particles of powder adhere to the adhesive ink and form an inscription.

Solutions of sucrose, glucose, and gelatin can be used as such ink.

Practical part.

From the Internet I learned that invisible ink was used in ancient times. People came up with and invented new ways to hide what was written.

Some invisible inks require chemicals to make, while others require natural substances. And it turns out that there are several methods for preparing invisible ink that can be easily applied at home, using quite affordable materials.

Here are some recipes that every child can use to make disappearing ink:

Invisible ink from lemon - squeeze the juice of half a lemon and dilute it with the same amount of water, develop with heat;

Invisible ink from onions - prepare onion juice and use it as ink, develop with heat;

Invisible ink from milk - take milk and use it as ink, dry it, develop it over a candle or lamp;

Invisible ink from soda - prepare a concentrated solution of soda - 1 teaspoon per 10 ml. - 2 - 3 teaspoons of water, move everything, use as long-lasting ink, develop with heat.

I decided to use some homemade recipes and see if I could make this ink myself. I will also try one way to create invisible ink using chemicals, using the chemist's kit I have.

Making invisible ink at home.

Experiment 1

Making invisible ink from lemon juice.

For the experiment you need: lemon, glass, brush, white sheet of paper, water, iron.

Squeeze the juice from the lemon into a glass and add the same amount of water. Dip the brush into the resulting solution and write or draw something on paper. After this, leave the paper with the inscription to dry.

After drying, take the paper and heat it with a hot iron.

Citric acid darkens when exposed to temperature, thus making the ink visible.

Lemon juice smells pleasant, is not noticeable when it dries, but it takes a long time to dry and appears as a faint yellow-brown tint to the letters.

Experiment 2

Making invisible ink from milk.

For the experiment you need: milk, a candle, a glass, a brush, a white sheet of paper.

Pour milk into a glass. Dip the brush in milk and write something on a piece of white paper. Let the milk dry.

After drying, there will be no trace or smell left from the letters. Then we take the paper and hold it over the candle. Gradually the inscription begins to appear. The inscription appears brown; this milk changes color when heated.

But the color of the inscription turned out to be not uniform, and using a candle is not very convenient and safe because you are constantly afraid that the leaf may catch fire; it is much more convenient to use an iron. But the experiment made it possible to prove that the inscription appears under the influence of any heat.

Experiment 3

Making invisible ink from lemon and iodine.

For the experiment you need: lemon, iodine, cotton pad, glass, brush, white sheet of paper, water.

Dip a brush into lemon juice diluted with water and write words on paper. After drying, the lemon leaves no visible marks on the paper. To read what is written, let's prepare a weak iodine solution by diluting the iodine with water. Soak a cotton pad in the iodine solution and rub it over the paper.

The paper turns blue, and the places where the inscription was made remain white. This is explained by the fact that the paper contains starch, and it becomes visible when reacting with iodine, and the places written with lemon do not stain.

Experiment 4

Preparation of invisible ink using phenolphthalein and ammonia.

For the experiment you need: phenolphthalein, ammonia, a brush, a white sheet of paper, rubber gloves.

Before this experiment, be sure to put on rubber gloves on your hands, since you will be working with chemicals.

I found the substance phenolphthalein in my kit; it turned out to be a white, cloudy liquid. I dipped a brush into it and wrote an inscription on a piece of paper. Let it dry.

Then I took an ammonia solution from my kit. Poured ammonia into the container. Here you need to be very careful, you need to do this in a ventilated area, since ammonia has a very pungent odor.

I held my piece of paper with the inscription over the ammonia. After some time, my inscription turned pinkish. After the ammonia wore off, the inscription became invisible again.

Ammonia dissipates quickly, so my inscription was visible for only a short time.

Experiment 5

Making invisible ink using a candle.

For the experiment you need: a candle, a brush, a white sheet of paper, paint.

I made an inscription on a white sheet of paper with a white candle. The leaf remained white. Then I took a brush, paints and painted the sheet with paint. The entire sheet was colored, except for those places where it was written with a candle. The text became easy to read against the background paint.

Conclusions.

1). You can make invisible ink at home from readily available household substances. I used milk, lemon, iodine, and a candle. Moreover, even a child can make them.

2). But not all types of invisible ink can be made at home. Some inks require chemicals that are not readily available at home. Some require ultraviolet lamps, which are also not always available at home.

3). In the course of my work, I became convinced that experiments are a very exciting and interesting activity. But it is better to conduct them together with adults, since heating elements were used for the experiments, and in one experiment, chemicals.

4). When developing ink with heat, it is more convenient to use an iron than a candle, since holding the paper over a fire risks the paper catching fire.

5). When heated, the substances contained in lemon and milk are destroyed and turn brown. And the starch contained in paper turns blue when in contact with iodine.

Conclusion.

In the course of my work, I studied the history of invisible ink and what types they come in. I learned many ways to make invisible ink and I made some of them myself at home.

Thus, I completely confirmed the hypothesis put forward at the beginning of my work: invisible ink exists and can be made at home.

The purpose of my work was to conduct experiments on the production of invisible ink, and I achieved my goal in the process of this work.

List of used literature and Internet sites.

https://ru.wikipedia.org

http://cryptohistory.ru/

http://www.krugosvet.ru/enc/nauka_i_tehnika/tehnologiya_i_promyshlennost/chernila.html?page=0.1

http://www.patlah.ru/etm/etm-13/dom%20tipografia/sekret%20cernil/sekret%20cernil.htm

Instructions for the set “Large Chemical Laboratory”

How many times in childhood did we read adventure books about Tom Sawyer, Electronics, Timur and his team. How they loved these cheerful and mischievous boys. Well, who hasn’t imagined themselves as a book hero, a pirate or a spy? They played war games, hide and seek, catch up, Cossack robbers. As we grew up, we began to forget how great it is to retain that genuine and radiant joy of a child. In this article we would like to invite you to plunge into your barefoot childhood and make invisible ink at home. You must definitely involve your children, brothers, and sisters in this fun process. The more people, the more fun the process.

Invisible ink

So, we will make ink, but not simple, but invisible! Interesting? Then we prepare everything we need.

We will need:

• half a large lemon;
• water;
• tea spoon;
• soup plate;
• cotton buds;
• paper;
• desk lamp.

After we have prepared everything, let's start our “chemistry”. Squeeze lemon juice and add one teaspoon of water to a deep plate. Mix the water and lemon juice thoroughly and dip a cotton swab into the mixture. Now write your message on white paper, wait until the message is completely dry and completely transparent. Now comes the fun part. To read this message, you need to heat a piece of paper under a table lamp, and it will reveal the message.

How did it work? Since juice is a “consequence” of organic chemistry, one of its properties is to produce a brown tint when the temperature rises. Then diluted with water so that our message instantly dries and disappears from sight.

Second way

This time we will do without lemon, but we promise that the effect will pleasantly surprise you.

So, we will need:

• gauze;
• grater;
• young onion, one small head;
• paper;
• water;
• soup plate;
• teaspoon;
• desk lamp.

Recipe

Grate one head of young onion onto a fine grater. Now take a gauze and put grated onion in it, squeeze out the juice. Mix the resulting juice with water, the proportion is one to one, stir in a deep plate. Write the text with a brush and let it dry for about twenty minutes. Now bring it to the table lamp, wait a minute and read what you have in mind. The onion juice in this experiment can be replaced with orange juice, as well as milk. Milk always makes good ink.

Option with soda

In our home “chemical laboratory” we will consider several more options. So, the soda option.

For this we need:

• baking soda;
• toothpick or cotton swab;
• water;
• White paper.

Mix baking soda and water in equal proportions. Using a cotton swab or toothpick, write text on paper using the mixed solution as ink. Let the lettering dry for ten minutes. Now you can view it, as in the previous methods, under a lamp. And you can make the experience much more interesting. Take black grapes and squeeze the juice out of them. Paint all the white paper with this juice and wait five minutes. And, lo and behold, you will see a bright contrasting inscription that appears before your eyes.

For those seriously interested in invisible ink and adventure games, you'll love the ways in which a huge range of different chemicals can be used as the basis for mysterious data transfers. Many substances are suitable for such games, but advanced spies simply need to be aware of the effects of acid.

You can read almost all invisible texts if you apply acid to them (for example, lemon juice). Well, as you concluded from the options discussed, most letters open when heated. So before you get ready for a hike, a secret mission or reconnaissance, be sure to take a source of light, heat and acid with you. Also, before an important task, don’t be lazy to run into the laboratory, because the agents have already prepared magic drugs for you.

List of magical developers:

• a pile of washing powder;
• phenolphthalein (reacts with soda, due to which it manifests itself beautifully);
• apple cider vinegar or acid (reacts with red cabbage juice and develops colorless ink);
• table salt (silver nitrate is enough to read messages);
• copper sulfate (you will need sodium iodide or ammonium hydroxide);
• ferrous sulfate (reacts only with soda);
• corn starch (you need iodine solution to read).

So we have looked at the simplest and most entertaining ways to make invisible ink. We hope that you found a lot of useful information and now the impressions of the experiments will remain in your memory for a long time.

Video on the topic of the article

Thematic selection of videos:

Invisible ink is a collective name for compounds that, once applied to paper, are invisible to the naked eye and appear after treatment with reagents or changes in temperature. Similar writing instruments were used in diplomatic correspondence and intelligence.

Below are simple recipes available to all novice spies and conspirators. The necessary ingredients can be found in every kitchen, found in any chemical kit, or purchased at the nearest pharmacy.

Read also:

Invisible ink recipes

So, what can we do with our own hands at home? And a lot of things!

Cow material

Pour some milk into a glass. We write the secret message with a thin brush or a cotton swab; in extreme cases, a toothpick, a feather, or an ordinary sliver will do.

Having entrusted information to a piece of paper, it should dry thoroughly, preferably without resorting to direct sunlight: ultraviolet radiation is destructive to spy secrets. After making sure that the milk is dry and invisible on the paper sheet, you can send it to your accomplice.

You can make text visible by heating the paper. In our hasty times, this is usually done using an iron.

Sometimes a secret document is put in the oven, heated near a light bulb, and if the message is not so urgent, it can be placed on a warm radiator. True fans of spy traditions use a candle flame and nothing more.

"Juicy" ink

After cutting the lemon, squeeze the juice into a cup, add a few drops of water, and stir. We can use a fresh apple in a similar way: after grinding the fruit on a fine grater, we squeeze out the juice we need. If you don't have an apple, you can take an onion.

You will have to experiment a little with the ratio of juice and water: if the concentration of acid in the composition is too high, the fresh inscription will stand out against the background of the paper and will no longer be secret, otherwise the developed text will turn out unclear.

The time spent is repaid by the ease of use of the resulting solution: if you are too lazy to fiddle with brushes and sticks, you can pour it into a fountain pen. After writing, dry. Develop by heating the paper.

Rice to work!

The ancient Chinese once again confirmed their status as the wisest people on the planet by combining the exciting and therefore energy-consuming process of writing a secret message with cooking.

Thick rice porridge was cooked in such a way that some of the liquid remained on the surface without being absorbed into the rice. Dipping a brush into this liquid, they wrote a message. After completing the work, the narrow-eyed spy wiped the sweat from his forehead, left the paper to dry and, after offering a short prayer to Buddha, began to eat.

The “delicious” recipe for invisible ink did not remain a Chinese monopoly for long; it was soon borrowed by scouts from the islands in the east.

So the young spy, devouring another portion of porridge left after a secret writing session to the delight of his mother, can rightfully consider himself a successor to the ninja traditions.

In ancient times, the “rice” inscription was developed by heating the paper. But the white-faced devils came up with an innovation here too: they began to cover the leaf with iodine. The text now appears more clearly.

Time-honored invisible ink recipes are listed. Let's move on to more modern methods in the style of James Bond.

Other recipes

There are other options for making ink. We have a dime a dozen craftsmen!

From... soda

Mix water and soda in equal proportions. We apply the text to paper and dry it in the shade. It is curious that the usual heating for developing text will not help, you should resort to help grape juice. By applying the juice with a brush over the entire surface of the leaf, we can read the message.

Starch

Add one part water to two parts, stirring, heat the resulting mixture over low heat, let it cool. Apply the text with a toothpick, match, or any wooden stick.

For manifestation cover the paper with iodine. The leaf will take on a delicate purple hue. The inscription will be dark purple.

Vitriol

Add a couple of pinches of copper sulfate to a glass of water, stir thoroughly until the crystals are completely dissolved. Apply the inscription with a brush, a cotton swab or a fountain pen filled with a solution. Dry in the shade. For manifestation hold the leaf for some time over a container with ammonia, under the influence of the vapors of which the text will turn blue-green.

Instead of washing

We dilute regular bleaching washing powder with water, make an inscription, and dry it in the shade. The text can only be seen under the light of an ultraviolet flashlight.

We use aspirin

Dissolve in water a regular aspirin tablet, and invisible ink is ready. We apply the text and dry it. You can read the message after treating the paper with a solution of iron salts, which are found in powder form in almost every chemical kit.