IN this thread the topic of appropriate gas filler material for light bulbs is being discussed. A common notion that it’s a bad idea to actually touch halogen bulbs with your fingers when installing them is also brought up. One person indicates the finger oils and salts will “etch” and weaken the bulb.
As indicated in the link below I had always heard it was simply that the oil layer left by the fingers would cause the bulb to heat unevenly and cause surface stress on the bulb.
These warnings always seemed a bit strange to me as I wondered how an infinitesimal sheen of oil would really stress the bulb instead of just being instantly vaporized by the high heat of bulb when turned on.
In researching this person who appears authoritative, says the whole “don’t touch” warnings are urban legends.
To be honest the last comment makes the most intuitive sense to me. Is there hard scientific evidence that touching a halogen high temperature bulb degrades or stresses it or is this simply a commonly accepted “fact” repeated and believed by everyone (including distributors) without verification?
I don’t know exactly what the cause is, but I was told that the salt in the oil from your skin relfects too much heat back into the bulb. It doesn’t “bubble” anything, just makes the bulb burn out within a few seconds. You’re supposed to wipe the bulb off with alcohol before powering it up, after installing it.
…I have done it (with my first Mag-Lite) and seen/heard of others doing it too.
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We used to use mercury vapor lighting at a large construction site, these “bulbs” were very sensitive to any foreign material on the surface. The oil from your fingers would definitely cause them to burn out very quickly. I think the same is true of halide lights. I use those compact flourescents in my home and I’ve never been particularly careful not to touch them, they last for several years.
I’ve replaced halogen bulbs and found beautiful thumb prints etched in brownish black on their surface. I can’t say that was the immediate cause of failure, but when you make part of a bulb’s envelope opaque heat has a harder time getting out.
In my hands, halogen lamps usually need to be replaced when metal vaporized from the heater forms a shiny-dark silver coating on the envelope. The lamp doesn’t explode, but runs hotter and hotter for less and less light. This is a positive feedback process since running hotter increases the rate at which metal evaporates from the heater. Leaving a fingerprint on a new bulb simply gives the feedback process a jump start.
My understanding is this happens more when the bulb is ‘short cycled’, if left on long enough the metal* will revaporize and recondense in differing spots on the buld including back on the filiment. During short cycling the metal from the filiment heats up enough to vaporize, but the metal on the glass does not. but condenses on the cooler glass.
By metal I mean whatever that silvery stuff is.
BY adding any contamination to the bulb you create a temp difference and differing rates of this stuff gets deposited, which would tend to exagerate the temp difference.
Halogen lamps used in television lighting definitely do not like fingerprints. I have replaced burnt out lamps with fingerprint shaped bubbles. I’ve always heard it was from the skin oil. The lamps we usually used came wrapped in little slips of paper slightly shorter than the lamp, so you could re-lamp without touching the bulb.
Yep. I used to tech for a small local cable TV station. I’ve seen them on rare occasions actually shatter quite violently, presumably as the result of finger oils. There’s nothing quite so…startlingly exhilarating than being under one when this happens. Wakes you up, for damn sure.
I replace a wide variety of light bulbs in my job and the most common type to fail are the halogen bulbs. We have found that bulbs touched with the bare hand will get hot enough to melt the solder in the base of the bulb. The reading lights in airplane PSU’s are the most common location. Map and chart lights in the flight deck and the emergency slide lights on the exterior fuselage are other common places for halogen bulbs. When defective bulbs are replaced, I wear white cotton gloves and clean the bulb with isopropyl alcohol after it is installed. I do the same during the rare chances I come across halogen bulbs away from work.
The source of this notion was quoted in the OP as saying “It’s an urban legend that bulb life of halogen lamps is shortened by finger oil.”
If we’d been hearing the no-touch advice only through word of mouth and internet messages, he’d possibly have a point. But when the advice comes from OFFICIAL MANUFACTURER’S INSTRUCTIONS, it’s not an “urban legend.”
Note that “urban legend” does not necessarily mean false. Some urban legends are true. That the above source quoted doesn’t know the difference between the meaning of “urban legend” and “false” (which is apparently what he meant) drops his credibility significantly in my eyes. If he can’t get his terms right, I don’t have much confidence he can get his facts right.
It’s not just an *urban *legend; halogen bulbs in suburban and rural areas are mostly subject to the same conditions. (When did “myth” get retired from the language and replaced by “urban legend”?)
Um, the fact that an official source helps to spread something doesn’t mean it is not an urban legend. Schools have sent home warnings about LSD in stickers: HOSPITALS have warned about needles in candy, Reader’s Digest and Dear Abby between them spread Urban Legends across the globe.