What would cause a light bulb to explode?

Benjamindaines

macrumors 68030
Original poster
Mar 24, 2005
2,837
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A religiously oppressed state
Last night I was watching Indiana Jones and the Kingdom of the Crystal Skulls (longest title ever!) when I hear that loud BANG; I got up and looked around the house and didn't see anything wrong so I went back to watching my movie. This morning I went into the bathroom and noticed that there was glass all over the sink and that one of the light bulbs was gone (save for the metal bit still in the fixture). What's really stumping about this is that the light was not on when it exploded! A bit like spontaneous combustion, but in light bulb form. It was just an ordinary filament light bulb (60 watts I believe); one of the round bathroom styles ones. Does anyone have any clue as to what could cause a lightbulb to explode when there is not power running to it? :confused::confused:
 

EricNau

Moderator emeritus
Apr 27, 2005
10,652
37
San Francisco, CA
It wasn't on? ...Had it recently been on?

The gases inside could have expanded (due to heat) and broken the glass.

...Just a guess.
 

Rodimus Prime

macrumors G4
Oct 9, 2006
10,136
4
first off remember the inside of a light bulb is at much lower pressure than the air around it which is where both the bang come from and the fact it keeps the bulb under constant load.

At some more micro fractures appeared in the glass at some point. Because of the constant pressure the cracks kept growing to the point where they reach critical and the glass of the bulb failed and it went boom.
 

iJohnHenry

macrumors P6
Mar 22, 2008
16,532
18
On tenterhooks
Yes, a flaw in the glass, fractured due to heating/cooling.

Take care removing the brass fitting. Some use a piece of potato, inserted into the cavity, to twist it out.
 

Benjamindaines

macrumors 68030
Original poster
Mar 24, 2005
2,837
1
A religiously oppressed state
It wasn't on? ...Had it recently been on?

The gases inside could have expanded (due to heat) and broken the glass.

...Just a guess.
Hmm, well the bulb was actually a burnt out one I just hadn't gotten around to fixing.
This happened to me once. I think it had something to do with the rapid cooling of the bulb or something.
Perhaps it was weakened at the base and just fell out of the base?
 

Rodimus Prime

macrumors G4
Oct 9, 2006
10,136
4
Hmm, well the bulb was actually a burnt out one I just hadn't gotten around to fixing.


Perhaps it was weakened at the base and just fell out of the base?
read my post. It explains it. even being burnt out the micro fractures where there and growing. It just got past the critical point and it failed.
 

Leareth

macrumors 68000
Nov 11, 2004
1,569
6
Vancouver
Wow

freaky coinsidence

I had a lightbulb explode today while I was taking a shower in the bathroom.

little pieces of glass everywhere, which of course I had to step on.
 

wordmunger

macrumors 603
Sep 3, 2003
5,124
2
North Carolina
read my post. It explains it. even being burnt out the micro fractures where there and growing. It just got past the critical point and it failed.
I don't think that's what happened. Much more likely is that the damage was catastrophic at burnout time -- the bulb had already "exploded" and was sitting intact in the base, balanced precariously on its own shattered shards. Then at some point it just fell out and smashed on the counter, creating the second "explosion" later.
 

Gray-Wolf

macrumors 68030
Apr 19, 2008
2,603
2
Pandora, Home Tree
If you need to remove the broken part, use a rubber handle screw driver handle first, and it should grip it just fine and not get shocked, even if the power is on.
 

Doctor Q

Administrator
Staff member
Sep 19, 2002
37,916
4,159
Los Angeles
Wirelessly posted (holmes/3.10.1 (OnetSzukaj/5.0; +http://szukaj.onet.pl) QTEK S100)

From the instructions:
What You Need:

1 raw potato
1 knife
1 replacement light bulb
1 bag for trash/glass shards
Gloves
Protective eyewear
Vacuum/sweeper and a dustpan
Recipe using the remaining half a potato is optional​
 

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