The Mystery of the Disappearing Lightbulb
July 15, 2017 12:08 PM   Subscribe

Last night I heard a loud THUNK like a projectile being released from a spring clip, and the lights went out on one of the circuits of the house.

I went downstairs and reset the fuse, came back up and it was the back bedroom light burned out. I went to bed.

Just now, I changed the bulb and found that the bulb itself had disappeared, leaving nothing but the metal fitting in the socket.

There is no trace of the bulb anywhere in the room, neither whole nor in the form of broken glass.

I didn't cut myself removing the metal fitting, because there were no jagged edges. In fact, there was no glass left there at all.

posted by tel3path to Home & Garden (16 answers total) 4 users marked this as a favorite
Are you sure the light burned out last night? When did you last see that light turned on? Could it just have been that you just noticed it last night, and it actually broke weeks ago?
Possibly someone broke it and cleaned up the mess, have you had any work done in that area?
posted by FallowKing at 12:20 PM on July 15

It's possible the light was on when it burned out.

Nobody else broke it and nobody else cleaned up any mess. No work has been done in that area.
posted by tel3path at 12:26 PM on July 15

Do you have a Roomba?

sorry, saw this on Jonathan Creek
posted by TWinbrook8 at 12:30 PM on July 15 [3 favorites]

This happens. In that case, the lightbulb was believed to be off, also. The mystery with yours is no debris. But if the theory expressed in the first linked Macforum is correct, there were microscopic fractures, presumably right at the point where the bulb connects to the metal, and (remember how fractures can travel in a car window) eventually the fractures reached the breaking point. The bulb would have fallen down to the floor whole. With some luck, rather than shattering, it survived. Here's another case where the glass survived whole. This can happen even if it hit a hard surface rather than a rug. Glass is funny that way.

So I am going to bet that a thorough search of the room will turn up the bulb, under the bed, under a dresser, someplace it rolled to. Or maybe it bounced and landed in the waste basket. (Or bounced out the window if it was open.)
posted by beagle at 12:47 PM on July 15 [8 favorites]

Yes, this has happened to me too, although in my case, the bulb (intact) landed on the carpet under the light fitting.

If if fell from a ceiling light fitting, might the bulb not be on top of something?
posted by Fuchsoid at 1:02 PM on July 15

With some luck, rather than shattering, it survived. Here's another case where the glass survived whole. This can happen even if it hit a hard surface rather than a rug. Glass is funny that way.

I used to have a living room with a high ceiling lit by 'decorative' bulbs ~4 inches in diameter, and over the years of changing them, I dropped several burned out bulbs 7+ feet onto a hard maplewood floor and noticed a curious thing.

The bulbs would drop and I'd hear them hit, and then a beat later I'd hear them shatter. I finally concluded that they were breaking on the second bounce, and my explanation for this is that the first bounce set the bulb vibrating, and the second bounce broke it because the vibrations caused the relative velocity of the bulb surface at the point of impact compared to the floor to be much, much greater than on the first bounce -- so I agree that the intact bulb probably rolled off somewhere a lot farther away than you'd think possible.
posted by jamjam at 1:16 PM on July 15

The light fixture is directly above a patch of carpet. The room is small and densely packed with junk.

It is not in plain sight under or on top of any furniture. I've moved every item in the room that can be moved short of a major declutter.

For this to have happened it would have to have found its way behind something that doesn't look like it can be gotten past.

So I'm guessing that's what it will take to find the bulb - a major declutter.
posted by tel3path at 1:22 PM on July 15 [2 favorites]

Safety note: when removing an exposed metal base from a light socket - be sure to turn OFF the circuit breaker.

Sequence you describe. . .

My assumption: THUNK you heard was sound of the (fuse in your description) circuit breaker itself tripping. It is common for them to make noises like that. The noise vibrations can travel quite a ways especially if your service is in metal conduit.

Assumption: Cause of circuit breaker tripping? Unknown at this point. It is unlikely that a glass globe dropping would cause the breaker to trip.

The glass globe is usually held into the metal base by a cement mixture and two wires soldered to the end of the bulb and to the metal base. I have had a good number of bulbs become un-cemented and twist off in my hand. I think it is pretty rare for both the cement and the wires to give way without someone twisting on the bulb or something hitting it somehow.

Generally the filament is the weakest link in the electric circuit and will be the first to disintegrate. And the filament giving way should not cause the circuit breaker to trip. The circuit breaker should trip if there is too much current flowing in a circuit, not when the light bulb burns out causing less current to flow.

What other things powered on when that circuit breaker was reset? Could there have been an air conditioner or other appliance on that circuit?

Let us know if you find the bulb!
posted by tronec at 3:21 PM on July 15

Other things on that circuit: quite a few, including one of several lights in my room, the hall light, (I think) the bathroom light, the downstairs hall light, the living room light, the dining room light, the under-stairs light and the kitchen light.

The bathroom, hall, and one or two of the downstairs lights could have been on. There are a number of appliances on that circuit, any of which could have been on, but I don't think they were. I really doubt anything was on that draws a lot of power. I was the only one up.

Other candidates (which I'm not sure are on the same circuit) include the dishwasher and nothing else. I don't even think the dishwasher was running. A number of things could have been on standby.

It is my experience that when a bulb burns out it usually does trip the circuit it's on. I've never heard it do so with such a loud bang before, though.

I doubt anything could have hit the bulb because it was protected by a sturdy china lampshade and there is nothing above it.

The tel3mum keeps on and on demanding that I MUST get the metal stepladder and carry it upstairs every time I change a bulb, and I must not stand on a wooden chair because that's far too dangerous. She went on and on at me this time too. Situations like these are exactly why I don't want to stand on a metal stepladder. And yes I did turn off the breaker for the occasion. It's a good thing I was here to change the bulb instead of her, I guess.
posted by tel3path at 3:42 PM on July 15

If you still have the metal fitting, look inside it for signs of burning, and also give it a sniff.

Because if the two wires leading to the bulb somehow shorted out inside the fitting, the heat and small explosion that would result could have loosened the grip of the resin and propelled the bulb out of the fitting fairly forcefully, and from there it might have bounced high off the patch of rug and ended up practically anywhere in the room -- and would also account for the thunk and the trip of the breaker.
posted by jamjam at 4:29 PM on July 15 [1 favorite]

No particular smell of burning, but there is some blackening of a small area of the resin.

There is also one wire-bit inside with what looks like sparks of copper dusted around it.
posted by tel3path at 5:07 PM on July 15

It is my experience that when a bulb burns out it usually does trip the circuit it's on.

That's very interesting, because I've probably had hundreds of bulbs burn out over the last four decades, in dwellings ranging from hundred-year-old Chicago flats to recently built suburban houses, and a burnt out bulb has never blown a fuse or tripped a circuit breaker in any of them. What kind of wiring do you have in your dwelling, and has an electrician taken a look at it recently?
posted by brianogilvie at 7:23 PM on July 15 [6 favorites]

We had a new system installed about 5 years ago. Everything is up to code. The house is Victorian-era.
posted by tel3path at 12:37 AM on July 16

Seconding never once had a burnt-out bulb trip a breaker, whether in new or old, well- or poorly-maintained, housing. That seems very strange to me (although the googles do imply it's possible; apparently if the filament in a bulb falls just-so it can cause an overload that trips the breaker). Consider getting a second opinion from a new electrician, one who is not associated with the work you had done?

(If it makes you feel any less weirded out, I once had the glass window to my oven door spontaneously explode several hours after I'd gone to bed, after not even using the oven for probably weeks. Slightly-damaged glass under pressure is its own special kind of magic.)
posted by sldownard at 7:44 AM on July 16

tel3path is in the UK. UK houses are wired very differently drom US ones. I don't recall the specifics, but that may have something to do with why he's used to a dead bulb taking the breaker with it whereas others are not.
posted by Anticipation Of A New Lover's Arrival, The at 10:22 AM on July 16 [1 favorite]

To be fair it usually trips a fuse, rather than the circuit for half the house. When bulbs burn out it's invariably been on switching-on whereas the projectile bulb was likely already on.

If bulbs were burning out constantly and tripping the fuse each time I would get worried, but IIRC I've been told to worry only if I have to reset the fuse more than once per incident.
posted by tel3path at 10:53 AM on July 16

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