Light bulb malfunction

[Oldylocks]

Can anyone confirm that the 40 watt appliance bulb pictured in this photo looks normal?

It still lights up so it's not burned out. I just don't know if I've ever seen a black burned-looking spot on a bulb like that. Maybe it's just about to burn out?

I just had the oddest experience in which this appliance bulb in my fridge melted through the plastic light casing that covers it. I was taking items off a shelf in there and noticed a melting plastic smell within about 4 minutes of having the door open. Within another minute, I identified the source of the smell as the light cover and immediately called the manufacturer, whose rep was very helpful and is graciously replacing the parts involved.

I am so curious as to what could have happened... can light bulbs "surge?" I've had that door open for longer periods than 5 minutes in the past. Nothing's been moved, so I can say with confidence that the bulb hadn't shifted in its socket. The fridge and the bulb are 3 years old, clean, and otherwise working fine. It really seems like the bulb all of a sudden produced way too much heat.

Anyone have a theory that doesn't involve appliance bulb gnomes or Justin Timberlake?

Thanks!

-Oldylocks

[Michael Daly]

It's not that uncommon, though you're probably more familiar with frosted bulbs and don't notice. The filament will keep losing material and it coats the glass. Once it gets too fine, one surge (as in turning it on) will cause it to pop. Some types of bulb get coated thicker and faster than others - Mini-Maglites (IIRC - krypton bulb) look silvered by the time they reach the end of their life.

Mike

[Oldylocks]

So can the bulb get hotter than normal when this happens?

-Oldy

[Jeff Wisnia]

I'd expect that as the filament lost material it's resistance would increase and the wattage dissipated would decrease, so it wouldn't get "hotter" towards the end of it's life.

But, maybe the coating on the inside of the glass doesn't let the heat pass through as well as clear glass, so the bulb glass gets hotter when it's coated?

The OP didn't say what parts the manfacturer is replacing. Maybe there's just something wrong with the plastic so as it ages it either smells when warm or changes so thatm it absorbs more light and heats up to the point where it smells. Or perhaps some foodstuff go smeared onto the plastic and then got rancid?

Too many variables here, 'eh?

Just my .02,

Jeff

[Jeff Wisnia]

Was the plastic shell is a location where someone could have overstuffed the refrigerator to the point where it got pushed against the bulb, but then sprang back out when the stuff was removed?

Jeff

[Oldylocks]

I just don't know if I've ever seen a black burned-looking spot on a bulb like that. Maybe it's just about to burn out? It's not that uncommon, though you're probably more familiar with frosted bulbs and don't notice. The filament will keep losing material and it coats the glass. Once it gets too fine, one surge (as in turning it on) will cause it to pop. Some types of bulb get coated thicker and faster than others - Mini-Maglites (IIRC - krypton bulb) look silvered by the time they reach the end of their life.

Mike Was the plastic shell is a location where someone could have overstuffed the refrigerator to the point where it got pushed against the bulb, but then sprang back out when the stuff was removed?

Jeff

[Jeff Wisnia]

Lemee know what he says, it's never too late to learn, and it'd be a gas if my guess about the inner coating absorbing heat has some merit.

I know the reason there's a "hands off" precaution for halogen bulbs is that finger grease on the outside of the glass absorbs IR energy and can get so hot that the glass melts in that spot.

Have you contacted lighting guru Don Klipstein?

Jeff

[Stormin Mormon]

found this in a different group but I though it was appropriate.

How many group posters does it take to change a light bulb?

1 to change the light bulb and to post that the light bulb has been changed

14 to share similar experiences of changing light bulbs and how the light bulb could have been changed differently

7 to caution about the dangers of changing light bulbs

27 to point out spelling/grammar errors in posts about changing light bulbs

53 to flame the spell checkers

41 to correct spelling/grammar flames

6 to argue over whether it's "lightbulb" or "light bulb" ... or another spelling

6 to condemn those 6 as anal-retentive

2 industry professionals to inform the group that the proper term is "lamp"

15 know-it-alls who claim *they* were in the industry, and that "light bulb" is perfectly correct

156 to email the participant's ISPs complaining that they are in violation of their "acceptable use policy"

109 to post that this group is not about light bulbs and to please take this discussion to a lightbulb group

203 to demand that cross posting to hardware forum, off-topic forum, and lightbulb group about changing light bulbs be stopped

111 to defend the posting to this group saying that we all use light bulbs and therefore the posts *are* relevant to this group

306 to debate which method of changing light bulbs is superior, where to buy the best light bulbs, what brand of light bulbs work best for this technique and what brands are faulty

27 to post URL's where one can see examples of different light bulbs

14 to post that the URL's were posted incorrectly and then post the corrected URL's

3 to post about links they found from the URL's that are relevant to this group which makes light bulbs relevant to this group

33 to link all posts to date, quote them in their entirety including all

headers and signatures, and add "Me too"

12 to post to the group that they will no longer post because they cannot handle the light bulb controversy

19 to quote the "Me too's" to say "Me three"

4 to suggest that posters request the light bulb FAQ

44 to ask what is a "FAQ"

4 to say "didn't we go through this already a short time ago?"

143 to say "do a Google search on light bulbs before posting questions about light bulbs"

1 forum lurker to respond to the original post 6 months from now and start it all over again

[Don Klipstein]

Is that image the offending bulb or another one of the same type?

Bulbs with that filament style sometimes have the "tip of the V" part of the filament short out. When that happens, the bulb gets brighter, produces whiter light and usually burns out soon. Heat output increases somewhat, with most of the extra heat being radiated rather than convected/conducted. If the bulb had a partial filament short and that made the difference in melting the plastic, then I suspect the design of the plastic casing that melted was marginal.

- Don Klipstein ( [e-mail],

[Oldylocks]

Don, you're one of the bulb experts I emailed about this! Small world. Thanks for your comments and answering my e-mail, Don.

The plastic casing is opaque white, somewhat flexible, and ~2 mils thick. It probably would melt easily if touching. I'm trying to determine if the bulb and the casing were in contact with each other but the way the casing melted in a big bubble makes that hard to figure out. When I receive the replacement part, I'll be able to tell. If they do touch, I'll have to take more things apart and see if I can move the socket a little.

I'm just a very unlucky person, I guess.

-Oldy

[Oldylocks]

... and one to say thanks for the laugh.

-Oldy

[PhotoMan]

Opaque? It now lets no light through?

[Jeff Wisnia]

I just can't resist that opening....

My answer is TWO...

See:

Jeff

[Stormin Mormon]

Was that X rated? It oughta be!