How does disappearing ink work?
Dissapearing ink - 4pt - img - PG.jpg
Figure 1: Example of disappearing ink disappearing over time.
Before we start of on this topic I think that you need to know what an acid and a base is, this will help you understand disappearing ink better disappearing ink.




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What is the difference between acids and bases?
1. Acid:
  • A lot of acids are found in fruits like citrus acid from the orange or lemon.
  • An acid can corrode metal.
  • An acid has a high PH level and can get measured.
  • An acid is the opposite of a base
  • A definition on an acid is: An acid is a substance that has hydrogen that breaks apart in water. When it breaks apart in the water it produces hydrogen that breaks apart in water to produce hydrogen ions.
  • Has a high PH (7 - 14);
2. Base:
a.opposite of an acid
b.When it meets water it makes hydroxide ions. These ions when they meet hydrogen ions they neutralize each other. When they neutralize each other they make water with salt in it.
c.Has a low PH (0 - 7).
d.Dissipates in water
ph scale - PG.png
Figure 2: The PH scale
Now that we got a good understanding of what a base is then now I can explain how Disappearing ink works.



How does Disappearing ink work?
Disappearing ink needs the carbon dioxide in the air to work right. When the carbon dioxide meets the water in the ink, it creates carbonic acid (CO2 + H2O → H2CO3). The carbonic acid reacts with sodium hydroxide in a neutralizing reaction, this then creates sodium carbonate, then thisfinally reacts with water making it clear(2 Na(OH) + H2CO3 → Na2CO3 + 2 H2O). When the carbon dioxide in the air meets the chemicals in Disappearing Ink they start becoming clear slowly. The time it takes to disappear varies depending on the amount of chemicals in it.

How do I make Disappearing ink?
1.You will need the following:
  • 0.10 g thymolphthalein for blue ink or phenolphthalein for red ink
  • 10 ml of ethyl alcohol
  • 90 ml of water
  • 20 drops of 3M sodium hydroxide solution (You can make this by dissolving 12 g of sodium hydroxide in ½ a cup of water) or 10 drops of 6M sodium hydroxide solution.
  • Something to test it on, a tee-shirt is recommended.
  • Ammonia if you want to make the ink reappear (also get a cotton ball)


2.How do I make disappearing ink with the materials above?
  • Take the thymolphthalein or phenolphthalein and dissolve it into the ethyl alcohol.
  • Add in the water and stir.
  • Add the sodium hydroxide solution drop by drop until the solution turns dark red or blue.
  • Test the ink on the tee-shirt (put a few drops of the ink on the tee-shirt).
  • Wait for it to disappear.


3.If you want the ink to reappear then do the following:
  • Take the cotton ball and dampen it in the ammonia.
  • Rub the cotton ball on the spot with the ink.
  • Wait for a little bit.
  • Watch the ink reappear!

What are the properties of good disappearing ink?
Good disappearing ink’s properties are:
  • Mixes with water.
  • Non-volatile, i.e. no pronounced smell.
  • Not easily seen in glancing light.
  • Invisible under ultraviolet light.
  • Does not decompose or discolor the paper.
  • Unreactive with iodine, or with any of the other usual developers.
  • Should not develop under heat.
  • Easily obtainable and has at least one use.
  • Not a compound of several chemicals.

What are some uses of Disappearing ink?
Dissapearing ink - 2pt - img - PG.jpg
Figure 3: Disappearing ink demonstration

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  • Hand stamping for re-entering a park
  • Some paintings when under UV lights
  • Books that make you read them in under 2 months
  • Writing a secret message
  • Parts of a kids book (part of a picture or the answer to a riddle, normally comes with a decoder pen).
  • And much moreWhite Coloring.jpg



Glossary

Phenolphthalein: Red Coloring.

Thymolphthalein: Blue Coloring.
Sodium hydroxide: a chemical compound with a high alkaline (Relating to or containing an alkali; having a pH greater than 7) content.



Citations
  • "acid and base." Compton's by Britannica. Encyclopædia Britannica Online School Edition.
    Encyclopædia Britannica, Inc., 2012. Web. 14 Sept. 2012.
  • Wikipedia contributors. "Mineral acid." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 23 Sep. 2012. Web. 24 Sep. 2012.
  • Wikipedia contributors. "Invisible ink." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 5 Aug. 2012. Web. 24 Sep. 2012.
  • Wikipedia contributors. "PH." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 26 Sep. 2012. Web. 27 Sep. 2012.
  • Newmark, Ann. Chemistry. London: DK, 2005. Print.
  • Challoner, Jack. The Visual Dictionary of Chemistry. 1st ed. New York: DK, 1996. Print. Eyewitness Science.