How bulbs and globes are vacuumed and sealed?

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A plasma globe or light bulb is sealed after the air is removed by a vacuum pump. Initially, a long neck is attached for the vacuum process. The glass neck is heated until soft while still connected to the vacuum pump. Once the air is evacuated, the neck is squeezed closed to create a seal. This process ensures that no air can enter or escape after sealing.
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How can a plasma globe or a light bulb made of glass be sealed after the air has been removed by a vacuum pump?
 
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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.
 
Is it sealed before or after the air is pumped out?
 
CognitiveNet said:
Is it sealed before or after the air is pumped out?

Think it through! (Hint, the process of sealing makes it impossible for air to get in or out...)
 
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.
 
CognitiveNet said:
Is it sealed before or after the air is pumped out?

I am glad I was not the only one who thought that question was odd.
 
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