Secrets of confidential ink, stealth ink

This special chemical was originally researched, manufactured and used by intelligence and counterintelligence industries to transmit confidential information, but today there are public applications in life.

A few words of history and language

Invisible ink is a special chemical, used to write on paper (or surface made of any suitable material as prescribed), right after writing, the message disappears. If the measure is compatible, the message appears. Of course, that message is often encrypted. On paper written with stealth ink, people write more about 'without affecting world peace' with the ink displayed.

The current US paper has printed with invisible ink, then see the ultraviolet rays

Since the end of World War I (1914-1918), intelligence and counterintelligence have been interested in using (writing, drawing and neutralizing) invisible ink. But in history, this technique has been mentioned by people since ancient times, such as the ancient Greek poet and writer Aeneas wrote in The defense of fortress in the fourth century BC. Other authors later, such as the Roman poet Publius Ovidius Naso (born in 43 BC , died in 17 or 18 BC) and the Roman philosopher, naturalist and military commander, were Gaius Plinius Secundus (23 - 79) commonly referred to as Pliny. He has noted information related to invisibility.

This special ink is available in several languages:

1. English: Invisible ink / security ink / sympathetic ink
2. France: Encre invisible / encre sympathique
3. Spanish: Tinta simpática / tinta invisible
4. Portugal: Tinta invisível
5. Germany: Geheimtinten / sympathetische Tinten
6. Russia: симпатические чернила / невидимы чернила
7. Japan: 不 可視 イ ン ク
8. Hoa: 隐形 墨水 (pinyin: yinxíng dungshui; Chinese-Vietnamese sound: Anonymity of ink)
9. Vietnamese calls security ink / security ink / invisible ink / invisible ink / invisible ink.

Classify

There are many ways to classify invisibility ink, which is not fully divided by the declassification method.

Detected by heat

Temporarily call thermal ink. It is most acidic liquids such as:

1. Lemon juice, apple, orange, onion.
2. Alcohol, vinegar.
3. Honey solution, sugar solution.
4. Soapy water.
5. Some soft drinks, such as Coca Cola.
6. Milk.
7. Body fluids like plasma.

Detected by chemical reaction

1. Lemon juice, starch are read when soaking paper in iodine solution.
2. Vinegar, ammonic is read with purple cabbage juice.
3. Table salt / rock salt, French call for chloride de sodium, English call for sodium chloride, molecular formula NaCl, read with silver nitrate notation - AgNO ₃ .

Detected by ultraviolet rays

This type of rays, Chinese call 紫外線 / ultraviolet, French call ultra-violet, English call ultraviolet (UV):

1. Lemonade.
2. Washing powder.
3. Soap.
4. Sunscreen.
5. Body fluids are saliva, plasma.

Properties and applications

During World War II (1939 - 1945), the UK's Special Operations Executive (SOE - founded in 1940) training manual lists 10 'ideal' stealth attributes:

1. 1. Soluble in water.
2. 2. No evaporation, ie no clear odor.
3. 3. No crystal deposition on paper, ie not easy to see under light.
4. 4. Invisible under ultraviolet rays.
5. 5. Do not decompose or discolor paper.
6. 6. No reaction with iodine or any other common detector.
7. 7. As few as possible methods of declassification, ie the word appears.
8. 8. Not a compound of certain chemicals, as this is a violation of section 7 above.
9. 9. Does not appear when exposed to heat.
10. 10. Easy to get and at least one reasonably secure public use for the owner.

Invisible ink is researched, manufactured and used by intelligence and counterintelligence industries, mainly for transmitting of course confidential information. However, in modern times, many important papers are still publicly used by stealth ink to combat counterfeiting, such as diplomas in Poland, US banknotes.