======Disappearing Ink======


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**Difficulty: **{{$demo.difficulty_description}}\\
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**Alternative titles:** Vanishing Ink Chemistry, Color-Changing Ink Prank
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====Summary====                   
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====Procedure====  
  - Dissolve 1 gram of thymolphthalein powder in 100 mL of ethyl alcohol, stirring to help it dissolve.  
  - Add 900 mL of water and stir; the solution may appear cloudy.  
  - Carefully add 10 mL of 3 M sodium hydroxide to turn the solution dark blue.  
  - Test the solution by applying a small amount to white fabric; watch as the blue stain disappears over time.  
  - For a faster effect, apply vinegar or blow on the spot to add carbon dioxide.  
  - Store the disappearing ink in a sealed container for later use.



====Links==== 
Disappearing Ink - Cool Science Experiment - SpanglerScienceTV: 
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📄 Disappearing Ink- Steve Spangler: [[https://stevespangler.com/experiments/vanishing-ink/]]\\

====Variations====
  * Use phenolphthalein instead of thymolphthalein to make pink disappearing ink.  
  * Adjust the fading time by adding very small amounts of sodium hydroxide.  
  * For a dramatic effect, trained professionals can use a carbon dioxide fire extinguisher to make the stain vanish instantly.



====Safety Precautions====
  * Always wear safety glasses when handling chemicals.  
  * Sodium hydroxide is caustic—handle with care and avoid skin contact.  
  * Only adults should prepare the sodium hydroxide solution.  
  * Wash hands thoroughly after handling chemicals.  
  * Test the ink on fabric before demonstrations, as some fabrics may show residue.  
  * Do not attempt the fire extinguisher method unless properly trained.




====Questions to Consider====
  * Why does the ink turn blue when sodium hydroxide is added? (The solution becomes basic, and thymolphthalein turns blue in basic conditions.)  
  * Why does the color disappear over time? (Carbon dioxide from the air forms carbonic acid, which neutralizes the base and lowers the pH, turning the indicator colorless.)  
  * How does blowing on the stain make it fade faster? (Exhaled breath contains carbon dioxide, which accelerates the neutralization reaction.)  
  * What happens if you add too much sodium hydroxide? (The ink will take much longer to fade because the solution remains strongly basic.)