Secret inks

Philo of Byzantium, a Greek military scientist, developed the world s first secret-ink recipe using the same type of formula. 

In general, secret inks derive from two reagents that produce a color. Sometimes one of the reagents is heat — the simplest ink is made by writing on paper with a solution of a colorless substance that chars when it is heated. Lemon juice works well for this purpose, and it was apparently used during the French Revolution. Urine does the trick, as well. Many a message has... 

Perhaps the most spectacular secret ink is Prussian blue, which forms by means of a chemical reaction between ferric sulfate and potassium ferrocyanide. Generally, a message written with ferric sulfate solution will be revealed when it is sprayed with ferrocyanide. A spy can soak fabric with each of these solutions and transport secret information without detection. During World War ii a German spy named George Vaux Bacon made notations on his socks and cloth buttons with the secret ink reagents. He, too, was caught and executed. 

Another secret-ink system used by the Germans during the war involved the chemical reactions between lead nitrate and sodium sulfide. As any high school student should know, solutions of these compounds are colorless, but form a black precipitate of lead sulfide when mixed. A spy can inscribe a message with the lead solution, and its recipient can read the missive by spraying it with the sodium sulfide solution. 

Fiore C, Poli A, Di Cosmo A et al (2004) Dopamine in the ink defence system of Sepia officinalis biosynthesis, vesicular compartmen-tation in mature ink gland cells, nitric oxide (NO)/cCMP-induced depletion and fate in secreted ink. Biochem J 378 785-791... 

Natural resins are generally described as solid or semisolid amorphous, fusible, organic substances that are formed in plant secretions. They are usually transparent or translucent yeUow-to-brown colored, and are soluble in organic solvents but not in water. The principal uses for natural resins are in varnishes, printing inks, adhesives, paper size, and polymer compositions. The term natural resins includes tree and plant exudates, fossil resins, mined resins, and shellac. They often have been altered from their original state during isolation and processing. For some appHcations, the resins have been chemically modified to increase their industrial utiUty. 

Geheimnis, /. secret, secrecy, mystery, geheimnisvoll, a. mysterious, mystic, occult. Geheim-rat, m, privy councilor, -schrift, /. secret writing, code, cipher, -tinte, /. invisible ink. 

Whether for a class demonstration, a practical joke, or perhaps a clandestine activity, disappearing ink is a fascinating substance. What is the secret to its action One formulation of disappearing ink contains a common acid-base indicator, that is, a substance that by its color shows the acid or basic nature of a solution. One acid-base indicator that shifts from a colorless hue under acidic conditions to a deep blue color in alkaline solutions is thymolphthalein. If the indicator starts off in a basic solution, perhaps containing sodium hydroxide, the typical blue color of an ink is perceived. How does the ink color disappear This behavior is dependent upon the contact of the ink with air. Over time, carbon dioxide in the air combines with the sodium hydroxide in the ink solution to form a less basic substance, sodium carbonate. The carbon dioxide also combines with water in the ink to form carbonic acid. The indicator solution responds to the production of acid and returns to its colorless acid form. A white residue (sodium carbonate) remains as the ink dries. 

There is also another defensive secretion that sea hares release less readily than ink. This is a milky white liquid called opaline, so viscous that it can be stretched out through the air into a long string. For sea hares, opaline is what is known as a defining characteristic, because all sea hares emit opaline whereas no other species are known to do so. In spite of its defining role, opaline remains poorly understood. It contains proteins and perhaps components derived from the animals diet the evidence here is in dispute. A sea hare releases opaline less readily than ink but seems to do so as a second response to serious predatory assaults. When touched by a sea anemone s tentacles, a sea hare discharges a shot of opaline, which causes the anemone s tentacles to contract. No one yet understands how opaline deters predators or what chemicals are responsible for its activity. 

Information on secret codes, invisible ink, and captured letters from the American Revolution. http //www.si.umich.edu/spies/index-methods.html... 

Perhaps the least rmderstood factor in the process of microarraying is the print buffer (probe ink) composition. This may not be too much of a surprise because manufacturers of computer printers offer consumers a multitude of different inks (whose formulas are closely guarded trade secrets) for use with a particular printer and kind of paper. In fact, it can be argued that the ink is perhaps the most important piece of the consumable product stream for this manufacturing sector. 

Ub Iwerks adapted xerography to eliminate the hand-inking stage in the animation process by transferring the animator s drawings directly to the cells. The first animated feature film to use this process was One Hundred and One Dalmatians (1961). At first, only black lines were possible, but in the 1980s, colored lines were introduced and used in animated features such as The Secret of NIMH. 

It is indeed true, that some good kinds of ink have been discovered by accident but those who devised them kept their composition secret, so that the public were either obliged to purchase those inks from the inventors, or to make use of such as were inferior in quality, and more or less perishable. 

Aplysia with chemical defenses in their tissues but without ink were consumed at a similar rate to those without toxins (20% vs. 12%), whereas those without toxins in their tissues, but with ink exhibited much greater survival (71%), suggesting that the excretion of ink may be the primary defense of these sea hares when being consumed by slow-moving predators like sea anemones.45 Pennings42 also found that ink from some (but not all) sea hares could deter predators, however he found no evidence that the metabolites responsible for defense were diet derived. Sea hares also secrete opaline when attacked by predators, although the function of this secretion has yet to be unambiguously determined.44... 

Nolen, T.G., Johnson, P.M., Kicklighter, C.E., and Capo, T., Ink secretion by the marine snail Aplysia califomica enhances its ability to escape from a natural predator, J. Comp. Physiol. A, 176, 239, 1995. 

The "Secret Committee" of the East India Company — under the direction of Lord Shelburne and company chairman George Baring — coordinated British secret intelligence s campaign of subversion and economic warfare against the newly constituted American republic even before the ink had dried on the Treaty of Paris (1783). (3)... 

Recent studies have examined the chemical basis of sea hare response to attack and have identified amino acid constituents in the opaline glands and ink secretions of A. californica that stimulate a false feeding response ( phagomimicry ) as well as confused behavior in the shiny lobster (Panulirus interruptus) 194-195 Both ink and opaline secretions are acidic, believed to enhance behavioral responses.196 The importance of inking as a deterrent mechanism is revealed by feeding assays in which reef fish consumed frozen mollusks but did not eat live specimens.43... 

The formulations of ultraviolet light-cured inks are proprietary, and at present, the best source of information as to their composition is the rapidly-growing patent literature. However, it is risky to infer the composition of inks used in tiie field from those described in the patent literature because only a small proportion of patented compositions ever become commercial products, and the compositions used in the field imy be the subject of patent applications not yet granted, or may be held as technical secrets without applying for patents. Nevertheless, the patent... 

The use of sympathetic inks reached a peak in the 18th century. These are solutions of dyestuffs which were said to exert secret effects the most famous is based on cobalt dichloride. They were for example used in the barometer flower which is described as follows by a contemporary writer ... 

---