======Lemon Juice Invisible Ink======


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**Materials: **{{$demo.materials_description}}\\
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**Alternative titles:** Secret Messages with Citrus
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====Summary====                   
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====Procedure====  
  - Cut a lemon in half and squeeze the juice into a small bowl.  
  - Dip a thin paintbrush into the juice and write a message on paper.  
  - Leave the paper to dry for 15–20 minutes without touching or covering it.  
  - Place the paper on an ironing board.  
  - With the iron on a high heat, have an adult carefully iron the paper for 15–30 seconds until the message appears.  
  - Allow the paper to cool for one minute before handling.



====Links==== 
Write Secret Messages With Invisible Ink! | STEM Activity - Science Buddies: 
{{youtube>AOVD7WgFP2s?}}\\

Lemon Juice Invisible Ink (Chemistry) - BeardedScienceGuy: 
{{youtube>poCnU_crpjQ?}}\\

📄 Invisible ink recipe - The National Archives: [[https://www.nationalarchives.gov.uk/education/families/celebrating-british-science-week/how-to-make-invisible-ink/invisible-ink-recipe/]]\\


====Variations====
  * Use orange juice instead of lemon juice, as in the Gunpowder Plot of 1605.  
  * Try other fruit juices (lime, grapefruit) to compare how well they work.  
  * Test different heating methods, such as holding the paper near a light bulb (with caution).



====Safety Precautions====
  * An adult should cut the lemon.  
  * An adult must handle the iron to prevent burns.  
  * Allow paper to cool before touching.  
  * Do not place flammable objects near the iron.




====Questions to Consider====
  * Why does the lemon juice message appear only after heating? (The carbon compounds break down and react with oxygen, turning the writing darker.)  
  * Would the message appear if you used water instead of lemon juice? (No, because water lacks the organic carbon compounds needed to change color when heated.)  
  * Why does citrus juice work particularly well for invisible ink? (It contains organic acids and carbon compounds that oxidize and darken when heated.)  
  * How might people in history have used invisible ink for secret communication?