Home > Invisible ink

The simplest forms of invisible ink are lemon juice and milk. For this type of 'heat fixed' ink, any acidic fluid will work. Write on paper with a fountain pen, toothpick or a finger dipped in the liquid. Once dry, the paper appears blank. The writing is made to appear by heating the paper, on a radiator, iron or oven for example, though a 100W light bulb is less likely to damage the paper.

Other types of invisible ink use different chemical reactions, usually an acid-base reaction (like litmus paper) similar to the blueprint process. These dual chemical ink/decoder pairs use a spray bottle for the decoding liquid or vapor (e.g. for ammonia fumes to decode phenolphthalein ink), or an invisible ink penThis article is about the writing implement. For alternate uses, see Pen (disambiguation). A pen is a writing instrument which applies ink to some surface. Terms and expressions Originally the word meant quill, and is derived from pinna (Latin for feather with two tips, one the encoding tip, and one the decoding. A cover message should be written over the invisible message, since a blank sheet of paper arouses suspicion.

Invisible ink is sometimes used to print parts of pictures or text in bookA book is a collection of leaves of paper, parchment or other material, bound together along one edge within covers. A book is also a literary work or a main division of such a work. A book produced in electronic format is known as an e-book. In library as for children to play with, particularly while they are travelling. A decoder penThe decoder pen yes-no pen yes-know pen or magic pen book is a combination of decoder pen or marker specially designed to reveal invisible ink-encoded pictures or writing, in the form of answers to questions or hidden parts of pictures, with specially cre is included with these books so that the children may rub the decoding pen over the invisible part of the text or picture, revealing the answer to a question printed in regular ink, the missing part of a picture, or the like.

Very rarely, invisible ink has been used in art. It is usually decoded, though when it is not, it makes a mockery of the concept of " visual art".

1 List of invisible inks

1.1 Revealed by heat

Some of these are organic substances that oxidize when heated, which usually turns them brown.

• Milk
• Lemon juice
• Onion juice
• Apple juice
• Sugar solution
• Diluted honey
• Diluted cola drink
• Vinegar
• Urine

Inorganic inks:

• Sodium bicarbonate solution
• Sodium carbonate (washing soda) solution
• Magnesium sulfate (Epsom salts)
• Salt solution- this focuses the heat so that the paper below them oxidizes faster
• Copper sulfate solution
• Ammonium chloride solution
• Iron sulfate solution
• Sodium nitrate solution
• Cobalt chloride solution
• Most dilute acids- these cause oxidation in the paper and heating makes the reaction proceed faster.

1.2 Developed by chemical reaction

In most cases, one substance changes color when mixed with an acid or base.

• Phenolphthalein, developed by ammonia or sodium carbonate.
  • Phenolphthalein (the main ingredient in laxative pills) is a pHAlternate uses: see Ph pH (potential (of) hydrogen) is a measure of the concentration of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S. Sorensen in 1909. The p stands for the German potenz mean indicator that turns fuchsiaFuchsia ''Fuchsia magellanica shoots with flowers (above) and berries (below) Scientific classification Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Myrtales Family: Onagraceae Genus Fuchsia Species About 100, including: F. alpestr pink in the presence of a base such as ammonia.
• Vinegar, revealed by red cabbage water.
  • Vinegar is an acid ( ethanoic acid, or archically acetic acid) that affects the pH indicator in red cabbage water.
• Ammonia, developed by red cabbage water.
• Copper sulfate developed by sodium iodide.
• Copper sulfate developed by sodium carbonate.
• Copper sulfate developed by ammonium hydroxide.
• Lead nitrate developed by sodium iodide.
• Iron sulfate developed by sodium carbonate.
• Iron sulfate developed by potassium ferricyanate.
• Cobalt chloride developed by potassium ferricyanide.
• Copper sulfate developed by potassium ferricyanide.
• Iron sulfate developed by sodium sulfide.
• Starch, developed by iodine solution (ink turns dark blue, paper turns light blue).
• Lemon juice, developed by iodine solution (ink turns white, paper turns light blue).