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Making invisible ink from lemon
Entertaining experiment To conduct the experiment you will need: half a lemon, cotton wool, a match, a cup of water, a sheet of paper.
Squeeze the juice from the lemon into a cup and add the same amount of water.
Dip a match or a toothpick with cotton wool wrapped into the solution lemon juice and water and write something on paper with this match.
When the “ink” is dry, heat the paper over the turned on table lamp. Previously invisible words will appear on paper.
cute ink
We have to admit that some types of ink have either long since disappeared from use, or are used only for such mysterious purposes as secret correspondence. There are many methods for this type of secret writing, and they all use secret or "sympathetic" ink - colorless or slightly colored liquids.
Secret (cute) ink
This ink has the property of producing invisible writing, which becomes noticeable only after special processing.
Blue ink
Inscriptions made with a solution of 1 g of crystalline cobalt nitrogen salt or cobalt chloride in 25 g of distilled water are completely invisible; When the paper is slightly heated, they acquire a bluish color, which disappears when cooled.
Cobalt oxides......................... 100 g
Nitric acid...................... 300
Dissolve and mix with the solution:
Sodium chloride......................... 100 g
Distilled water........... 100
What is written in ink is invisible. Develop by heating over a lamp.
Yellow blood salt......................... 10 g
Water................................... 100
Write with this solution.
To develop, wet the paper with the following solution:
Ferric chloride...................... 200 g
Water........................... 500 ml
Red ink
Write with a diluted solution of gold chloride and allow to dry. Written: disappears. After moistening the written areas with a solution of tin salt, inscriptions appear purple-red.
Mix 50 g of iodine tincture with a teaspoon of dextrin and filter. Anything written in such ink disappears within a day.
Dextrin, white or yellow powder obtained by processing starch; solution in water is a sticky liquid. To obtain dextrin, starch is heated to 180-200° or heated to 50° with dilute acids. It is used as an adhesive instead of gum arabic, for finishing fabrics and
leather, in the manufacture of inks and paints, to impart hardness and shine to linen, etc.
Grandfather Lenin's recipe
In childhood, for one whimsical game involving guessing the secret plans of their older revolutionary brother, little Ulyanov was given the nickname “Wizard” by the children. He dipped a clean quill pen into milk and wrote with it on a piece of white paper. The milk was allowed to dry, after which not a trace remained of the letters. Then Ilyich heated the paper over the glass of the lamp, and what was written clearly appeared on it.
Twenty years later, in a St. Petersburg prison, the old man again recalled his childhood. He broke a loaf of black bread, fashioned inkwells from the crumb, collected a white liquid in them, salty to the taste, and wrote with it between the lines in books on how to combat thrush. When the warden called his superiors to look at the quirks of the German spy, Lenin put the inkwell in his mouth. He moved his lower jaw with relish, never ceasing to praise the tsarist regime. Books were regularly handed over to the public. The workers whiled away the evenings free from meetings by reading them syllable by syllable at the firebox of the blast furnace. In the hidden text, the words of propaganda leaflets and the theses of the draft party program were vaguely discernible.
Secret Organizations' Recipe
Members of the secret organization “Black Redistribution” also used invisible ink in their correspondence. But due to the betrayal of one of the Black Peredelites, who knew the secret of deciphering the letters, almost everyone was arrested... The secret letters were written with a diluted aqueous solution of copper sulfate. Text written in such ink appeared if the paper was held over a bottle of ammonia. The letters turn bright blue due to the formation of an ammonia complex of copper.
Chinese recipe
But the Chinese emperor Qing Shi Huangdi (249--206 BC), during whose reign the Great Wall of China appeared, used for his secret letters a thick rice water that leaves no visible traces after the written hieroglyphs dry. If such a letter is slightly moistened with a weak alcohol solution of iodine, then blue letters appear. And the emperor used a brown decoction to develop letters seaweed, apparently containing iodine.
Ink Removal Recipes
Here is a recipe that allows you to remove seals, stamps and other notes from writing paper.
To obtain the specified liquid, you need to take 70% vinegar concentrate (about one teaspoon) and a small amount of potassium permanganate in crystalline form (at the tip of a knife). Specified substances mixed, and after that the liquid is ready for use. Under the section of the sheet of paper from which you want to remove something, you need to place a clean white sheet of paper. Then take a brush (the softer and finer the hair, the better for the job) and, dipping it into the prepared solution, begin to brush over the inscription until the inscription disappears. At this point the paper will acquire brown tint, which must be removed with a piece of cotton wool soaked in a solution of hydrogen peroxide. Then the section of paper moistened with the solution must be dried by ironing it with a warm iron. To do this, take a soft cloth, place a clean white sheet of paper on it, and then place on it the paper from which the inscription has just been removed. Then it is ironed (the surface of the iron must be clean).
Note: using this method, it is advisable to remove inscriptions only from thin sheets of paper. To remove inscriptions from thick sheets, it is more advisable to use a match instead of a brush, on the sharpened tip of which a small piece of cotton wool is wound (several such brush matches are made, because they quickly fail). The matches of the brush are moistened in the solution and, using gentle back-and-forth movements along the inscription, remove it.
TWO MORE RECIPES:
Recipe 1: take 10 g of oxalic acid, 10 g citric acid, 100 ml of water. Stir it all. Moisten the inscription with the resulting solution 2-3 times with a soft brush, then (also with a brush) moisten the inscription with water. After removal, dry the etched area with a blotting cloth.
Recipe 2: take 10 g of hydrochloric acid, 10 g of table salt, 30 ml of water. Stir all this and apply as the previous two products.
What is disappearing ink? This is a paste (liquid), when written, the inscription disappears without a trace after some time. People learned to use them for a variety of purposes in ancient times. There was always some secret associated with their use that no one should know about.
They were used to transmit love messages, which were kept in the strictest confidence, for encryption and exchange of valuable information.
Today, every schoolchild can make disappearing ink, because the secret of making it is completely simple.
Three simple secrets to creating invisible letters
Let's look at the most common ways to make disappearing ink at home. 
- Iodine-dextrin filtrate. We will need dextrin (1 teaspoon), iodine (medicinal solution) 50 ml and filter paper. Mix iodine and dextrin, shake thoroughly and wait for precipitation. Then we filter and use the resulting liquid as ink. They will disappear because iodine is very volatile, and it is this that provides the color. It takes about three days to disappear.
- Willow ink. We will need a small willow twig. It must be burned, and the resulting ash must be thoroughly crushed and diluted with water to such a state that it can be used for writing. Such inscriptions will disappear in about 5-6 days.
- Sympathetic alkaline ink. To prepare them, you will have to go to the pharmacy and buy several chemical ingredients. Namely:
- ethanol;
- aqueous solution of ammonia (ammonia);
- phenolphthalein (purgen);
- water.
Preparation: 100 ml ethyl alcohol mix with one teaspoon of purgen until the latter is completely dissolved. Then add water (50 ml) to the solution, one cap ammonia. The substance will turn bright red. Now you can write anything, anywhere with this ink. As soon as they dry, they will immediately disappear. 
It is important! When working with any of the listed substances, you must observe safety precautions and extreme caution!
Developing Ink Recipe
There are also inks that become visible only under certain conditions. The simplest example of a manufacturing recipe is as follows.
The proposed ingredients are stored in school chemistry classrooms, use only with the permission of the teacher!
Cobalt chloride (CoCL 2) or cobalt nitrate (CoNO 3) weighing 1 gram. Dissolve salt in distilled water, weighing 25 grams. That's it, the ink is ready. You can write a letter. But in order to see what is written, you will need to heat the inscription (put it on a radiator or hold it over the stove). The text that appears will turn blue. As soon as you cool it, it will disappear again.
Disappearing marker
You can order such a marker
Pens with disappearing ink are a fairly popular product today, located in the windows of most office supply stores. What is it? Pens with disappearing ink look and write just like regular pens. However, there is one caveat.
Pens with disappearing ink are indistinguishable from real ones.
So, what's the catch? Pens with disappearing ink leave exactly the same inscriptions as regular ones. However, literally after two or three minutes the ink begins to slowly lighten. After about ten minutes the inscription will no longer be visible. It is impossible to see it even in ultraviolet light.
Disappearing ink pens allow you to leave secret or confidential writing on documents if you need to remove them soon. In a word, temporary.
But it is worth noting that using such a pen on financial or legal documents is prohibited. This causes a violation of the law.
There are other options
However, you won’t necessarily get the result in ten minutes. There are different types of invisible ink. Much depends on the conditions environment. For example, ink will disappear faster in drier rooms than in humid ones. In the latter with the inscription, no changes occur for twenty minutes. The transformation begins after a certain period of time. The inscription becomes less visible after about an hour. It turns pale throughout the day until it completely disappears. But no matter how you look at the “inscription” after that: no matter what angles and no matter what lighting, you still won’t see anything. You just need to take into account the fact that if you press hard on the pen, it can leave grooves on the paper.
Naturally, it is impossible to illegally use invisible ink for any fraud. Special examinations They will definitely prove the presence of your signature.
Where is it used?
These ink fountain pens are very convenient if you need to hide some writing after a while, especially since on the outside they look like simple gel pens. In fact, those around you do not know that these pens are filled with ink that disappears when exposed to light.
Accordingly, they can be used for various peaceful purposes. For example, resourceful girls can use this pen to leave their phone number to annoying fans. It is very comfortable.
Or you can make fun of the teacher by attaching such a pen to the grade book. You can also play a fun prank on your botanist friend. He will be extremely surprised when the lecture notes disappear without a trace. The main thing is not to be offended. It's also a good idea to play a funny joke with your parents. Draw on the wallpaper and see how it reacts. In general, there are many options, all you have to do is show your imagination!
Is it possible to make ink yourself?
By the way, many people are concerned about one question: is it possible to make disappearing ink with your own hands? In fact, you can!
To do this, you need to mix a teaspoon of dextrin with 50 ml of alcohol infusion of iodine. The precipitate is filtered, resulting in blue ink. They lose their color a couple of days after the iodine evaporates.
There is another way. To prepare ink, you need to take a willow twig and burn it, and finely grind the coal that remains. Next, you need to dilute it with water to the consistency of ink. The inscriptions they made disappear after about six days. However, it is impossible to give a 100% guarantee. A small error in preparation - and the ink will not work!
Where to write?
Do inscriptions made with such pens disappear from everywhere? Of course, in order for them to disappear completely, it is necessary to write on paper. And even its density affects how quickly the inscription disappears. Although, as a rule, it depends much more, as mentioned above, on lighting and air humidity. In a word, a spy pen, a dry room and high-quality paper are all that is necessary for the inscription to quickly disappear.
Shelf life
And finally, regarding quality and shelf life. The pen with disappearing ink has extremely positive reviews. When used correctly, the ink retains its properties throughout the year. You just need to put a cap on it.
In a word, this wonderful pen, at first glance, is no different from the most ordinary one.
In order to write with it, virtually no pressure is required. Therefore, there are not even indentations left on the paper. As a result, after some time, the inscriptions made disappear without a trace, and any attempts to read them turn out to be pointless (even with the help of ultraviolet light).
By the way, such a pen can be an excellent gift for a child who loves to play spies. Adults with a sense of humor will also like this gift. You can even choose a special gift option: the stylish classic design of the pen and the beautiful but strict case will definitely attract the attention of your family and friends.
The cost of the accessory is relatively low. It all depends on the design you choose. In principle, you can easily meet 130-150 rubles. Agree, for such a unique item this price is simply excellent.
So if you want to do original gift or just have fun pranking your friends, the spy pen is just what you need! Buy it and you won’t regret it, don’t even hesitate! Well, your friends and family will definitely appreciate your sense of humor!
