How bulbs and globes are vacuumed and sealed?

  1. How can a plasma globe or a light bulb made of glass be sealed after the air has been removed by a vacuum pump?
     
  2. jcsd
  3. You first make it with a long neck where the vacuum pump is attached. Then you heat the glass of the neck until it becomes soft, closes the neck and seals the bulb.
     
  4. Is it sealed before or after the air is pumped out?
     
  5. Think it through! (Hint, the process of sealing makes it impossible for air to get in or out...)
     
  6. HallsofIvy

    HallsofIvy 40,308
    Staff Emeritus
    Science Advisor

    What a strange question! If you seal it before you pump the air out, you no longer have a way to pump the air out!

    The point is this- you mask a long thin glass neck, pump the air out, then, while the neck is still attached to the vacuum pump, with the vacuum still good, you heat the neck until it is soft, and use some tool to squeeze it closed.
     
  7. I am glad I was not the only one who thought that question was odd.
     
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