lamp failure


Senior Team Emeritus
Premium Member
So if you have a filament lamp that's all purple/blue/black and sometimes some silver coating on the inside of the glass, what was the cause of the failure?

If it's silver coating on the glass, often silver/black, what was that cause, the same or different?


Active Member
As for your first case of lamp failure, I believe that it is a seal failure. I have seen a lamp like that before and I am fairly sure that both the lamp that I have seen and the lamp failure you describe are seal failures. As for your second type, i am clueless.

Chaos is Born

Active Member
I want to say that the second one is just the metal getting too hot and basically vaporizing and leaving a burnt/unburnt metal on the glass.


Active Member
Sounds like what happens when you touch a bulb and the oil from your skin gets on the surface. That spot on the bulb will super heat and melt the glass.


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Sounds like what happens when you touch a bulb and the oil from your skin gets on the surface. That spot on the bulb will super heat and melt the glass.
But what about the inside?


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Premium Member
nobody finger [email protected]&ed these lamps - too common an expiation stop using it as a coverall, there are other ones such as the excellent ones above. Umm, super nova, even seen the results of a filament or ten shoot out the bulb on an incandescent or even halogen lamp as if a bullet hole left melted into the glass, and the other side where the opposing side of the glass puckered due to the pressure being sucked out forming like a “killroy was here” type shape. I'll post if I have a good photos of this and other below conditions.

More important in these cases of say vaporizing of the filament depositing itself upon the globe or a pinch seal hole, what's going on inside of the lamp at the time this happens, and what's the cause of the white frosting like, or purple black, or silver/black etc coatings? What is the cause of each condition - such concepts are to be aware of in solving problems rather than just replacing a bad lamp. Really cool to see such things, they are interesting to collect but also important to study and learn the cause of. Often beyond the finger touched lamp, or the blackened verses clear blown fuse concept as similar to lamps, you can diagnose in your own CSI type of way the cause of a lamp failure and solve problems in learning from the dead lamps. This also including especially lamp bases on bad ones for they often tell a lot.

Also given the photos, what would cause the below puckered filament gunshot and if I have it, the PAR 36, DWE lamp that failed in a as if touched type of way but as the capsule inside the lamp thus not touched. This given both the broken in half nature and other lamps within the fixture have never had that problem. So what in the photo caused the filament inside a PAR 36 lamp capsule to sort of blow thru the glass of the capsule, this within a sealed beam PAR lamp?

Further questions, I have had an EVR lamp that was no doubt finger [email protected]&ed, no doubt by my own hand early in my career, it continued to work even given this. What’s this, the filament of the lamp encased within the quartz glass of the lamp - really a cool thing screw the bench focus, it continued working. Anyway with the DWE lamp in the photos, what caused it’s final failure by way of not just filament encased within the capsule of the lamp and or it’s outer globe breaking in half? Say which came first, some pressure release within the lamp’s capsule by way of say an over-heated condition that forced the filament to stretch thru the capsule than have a pressure problem of expanding gasses that blew up the outer PAR lamp, or say the PAR lamps’s outer part that got say hit first which caused a rapid cooling of the capsule thus a sucking of the filament towards the cooler area thus melting it’s way thru the glass?

Chicken or the egg. One concept in some way implies an over heating of the lamp, the other concept implies a lamp while in use struck by something. This could be a very important question - use of the fixture verses it's sufficiency to cool what is used in it. Thus a CSI type mystery over just a simple what costs like two or three of us going out to lunch and paying for it lamp replacement costs. Gotta remember the human terms, days wage verses a single lamp. It effects in end result your pay by way of what's left in the budget and your being a professional sufficient to look after your own in saving money for your pay raise. This given the squeeky weel gets the oil and I just for the first time ever signed a refund recipt for some lamps. Long story, before now I never knew much about what I got full refunds on for lamps, it was always just absorbed into the budget. New accountant thus new concept in where is this refund for a few hundred dollars coming from? Sent them the tracking history of the lamps I got a refund on from in this case VeraLite. Lamps were bad within the first few hundred hours. I sent them back for full refund by way of tracking them and analizing their cause of fault as manufacturer defect. Lamps got that refund after inspection by the manufacturer - all lamps I send back get a refund, what's the question? Sure, I'll sign for money coming in verses money going out as normal...

This given I had to E-Mail my electrical supplier about more still Leviton porcelain lamp bases that due to crappy shipping came to me broken and I wanted credit for them. Beyond this, it's getting to be quite the collection of broken lamp bases out of the box, should I send them back in having saved them for this purpose, or just toss them out?

Note, the PAR 36 DWE lamp photos are still on my camera at work. Will update with the photos later. Until than, here is a bit to chew on that should be curious.


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Senior Team Emeritus
Premium Member
Following is a DWE PAR 36 lamp. Seemingly there was a heat problem which caused the inner capsue to go towards the front of the lamp where it was cooler. This proximity seemingly cracked the outer bulb.

Possibly it was a manufacturer defect in some way like a hole in one of the two globes and or a stress fracture of some type.

Any other solutions?
Nither solution seems to be adiquate.

Were it a fixture heat problem, other fixtures of the same type and or other lamps in the fixture or past lamps will have had the same problem. First I have ever seen a cracked in half lamp before with a filament bubbling out of it's capsule. Perhaps this was just pre-explosion in dying out in a one in a million way.

There is a third option: What if the lamp were struck while in use? In that instant before the lamp went bad, perhaps the inner capsule and filament in being really hot already got instantly blown as it were towards where it was suddenly cooler.

The bubble seems to have been sucked to where the lamp cracked in half and towards where it was instantly cooler as opposed to where at the rear of the fixture it will have been warmer. (the other half of the lamp is missing but given the clean break in it, most likely the lamp was cut into two or very few pieces instead of random amounts of smaller ones. Perhaps even a defect in the lamp allowing it to break all the way around.

Again, noting the bubble in the capsule - impossible anyone could have touched it. It's also not discolored at all.


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Senior Team Emeritus
Premium Member
Hey Ship,
In my experience for lamps here is what I have learned from vendors which may provide some answers or "suspects" to the causes... The discolorations are often the result of gas imbalances or leaks inside the lamp where air is introduced inside the lamp (the blue purple discoloration) or when the gas pressure inside the lamp decreases or leaks out but no air leaks back in to equalize, causing a deformation when heated of the glass and filament. During the Halogen effect because of the gas being lesser--this can cause tungston particle deposits to build up and accumulate onto the glass instead of back onto the filament hot spots as is supposed to occur (thus the silver discoloration coating the inside of the glass). If I recall, its iodine or bromine/bromide gas for most tungston lamps...but its been a while. The "white" discolorations I am told are because of moisture or humidity. That is how these issues were explained to me by folks Ushio....

As for your Par 38 lamp--couple of things to consider--if HOT or not--a severe shock or bump to the fixture or lamp can cause the filament to shake or displace itself in its hooks.. The filament remember is just a tiny coil which in reality if stretched out is significantly long in size comparatively--so its easy to stretch out the coil and disdend it. Think of a telephone coil handset wire right out of the bag--the coil if you leave it hanging between two points will succumb to gravity and pull lower over time from its original stretch--and if you bang into it, it will move and stretch under its weight and gravity and tensions...well same occurs in a smaller degree with a filament. So Gravity can also contribute as a factor and pull the filament into the glass and the glass will then bow outwards away from the filament as it heats thinning the glass until failure.. I've seen FCM's and FEL's that dont' fail because of finger prints, but because of age and being in one position a long while heated and cooled repeatedly, where one part of a coil in the filament just weakens towards the ground as if gravity plays a factor, and disdends down until its burned thru the glass and is exposed. The heat often generated in the filaments is around 4000 degrees give or take some depending on the lamp and composition...but that is significantly hot enough to have issues with from time to time..

Just a few thoughts on the subject.... :)



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Premium Member
Anyone want to agree, refute or modify Wolf's thoughts? Also, thanks for the reply. Lamp study in the demise of them is always a curious science for me.


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Lamp study in the demise of them is always a curious science for me.
It shall now be known as Lampology®

Who wants to make the Wiki?


Senior Team Emeritus
Premium Member
Anyone want to agree, refute or modify Wolf's thoughts? Also, thanks for the reply. Lamp study in the demise of them is always a curious science for me.

Would love to hear other thoughts and experiences and insights--again what I posted is what I had picked up over the years.... Not sure its entirely accurate or complete--but again felt I would help this topic by adding my two cents worth to carry the discussions further....

Always happy to reply.. ;) Understanding the "why's" of things is also a science for me as well....


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