======Disappearing Glassware======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Invisible Glassware, Disappearing Test Tube
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====Summary====                   
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====Procedure====  
  - Fill a large clear glass bowl with vegetable oil and place a Pyrex beaker inside so it will be hidden for a “reveal” at the end.  
  - Prepare three Pyrex beakers: one with water, one with water and oil (oil on top), and one left empty.  
  - Dip a Pyrex test tube into water. Point out that although it is less visible, it can still be seen.  
  - Dip a second Pyrex test tube filled with vegetable oil into the bowl of oil. Remove any air bubbles and ask whether the glass is still visible.  
  - Explain that Pyrex becomes invisible in oil because both have the same refractive index.  
  - As a finale, pull the hidden Pyrex beaker out of the oil for a surprise reveal.  
  - Discuss with students using key terms such as refraction, refractive index, and cloaking.



====Links==== 
Index of Refraction - disappearing glassware demonstration - Homemade Science with Bruce Yeany: 
{{youtube>9Tj2KMZhfoc?}}\\

The Disappearing Test Tube - MWMmaths: 
{{youtube>NqHex2Tqe5g?}}\\

📄 INVISIBLE GLASS EXPERIMENT - Puffing Billy Railway: [[https://puffingbillyrailway.org.au/wp-content/uploads/SCIENCE-WEEK-GLASS-EXPERIMENT-final.pdf]]\\


====Variations====
  * Use different clear liquids (e.g., glycerin, corn syrup) to compare visibility of Pyrex.  
  * Try the demonstration with other transparent materials like acrylic or plastic.  
  * Use colored light or lasers to make the refraction effects more visible.  
  * Connect the demonstration to forensic science by showing how refractive index is used to match glass fragments at crime scenes.



====Safety Precautions====
  * Take care handling oily glassware - it becomes slippery.  
  * Clean up spills promptly to prevent slipping hazards.  
  * Dispose of oil safely; do not pour large amounts down the drain.  
  * Use paper towels for wiping glassware; wash with soap after use.




====Questions to Consider====
  * Why does Pyrex disappear in vegetable oil but remain visible in water?  
  * What is refractive index, and how does it relate to the speed of light in different materials?  
  * Why does light bend when moving from one medium to another?  
  * How could this principle be applied in real-world uses such as forensics or cloaking technology?  
  * What would happen if the oil and glass had slightly different refractive indices?