======Thermal Processing of Bobby Pins======


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**Alternative titles:** Annealing and Quenching Steel Bobby Pins, Heat Treatment of Steel
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====Summary====                   
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====Procedure====  
  - Set aside one steel bobby pin as the control sample and do not heat it.
  - Hold a second bobby pin with pliers or tongs and heat it evenly in a Bunsen burner flame until it glows red-hot.
  - Keep the pin in the flame for about 20 to 25 seconds after it begins glowing.
  - Remove the pin from the flame and allow it to cool slowly in air on a paper towel. Label this pin as annealed.
  - Heat a third bobby pin in the Bunsen burner until part of it glows red-hot.
  - After heating for 20 to 25 seconds, immediately place the hot pin into a cup of cold water.
  - Remove the pin from the water, dry it completely, and label it as quenched.
  - Measure and record the width and height of the smooth side of the control bobby pin.
  - Set up each bobby pin so a cup can hang from the end using twine.
  - Gradually add pennies to the cup and observe how each bobby pin bends or fails.
  - Compare the behavior of the control, annealed, and quenched pins.



====Links==== 
Thermal Processing of Bobby Pins: Interactive Science Lesson 8 - Ceramic and Glass Industry Foundation: 
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Heat treatment of metal Bobby pins - Grant Paul: 
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📄 Thermal Processing of Bobby Pins Lesson - Ceramic and Glass Industry Foundation: [[https://foundation.ceramics.org/teacher-resources/free-lesson-plans/thermal-processing/]]\\

📄 Heat Treatment of a Metal Bobby Pin - Chemistry Comes Alive: [[https://www.chemedx.org/JCESoft/jcesoftSubscriber/CCA/CCA2/MAIN/BOBBY/CD2R1.HTM]]\\

====Variations====
  * Use different steel objects, such as paper clips, to compare results.
  * Heat the pins for different lengths of time to see how heating duration affects properties.
  * Test flexibility by manually bending the pins instead of using weights.

====Safety Precautions====
  * Safety glasses must be worn at all times.
  * Use pliers or tongs when heating metal to prevent burns.
  * Keep flammable materials away from the Bunsen burner.
  * Allow metal to cool fully before handling.
  * Use caution when working with open flames and hot water.

====Questions to Consider====
  * Which bobby pin bent the most under the same load? (The annealed bobby pin)
  * Which bobby pin was the most brittle? (The quenched bobby pin)
  * Why does slow cooling make the metal easier to bend? (Atoms have time to arrange into a softer structure)
  * Why does rapid cooling make the metal harder but more brittle? (The atomic structure is locked into a stressed arrangement)