# Touching halogen bulb causes premature failure. Urban legend or not? **URL:** \ **Category:** Factual Questions\ **Created:** [January 1, 2006, 1:49pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951 "2006-01-01T13:49:05Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 1, 2006, 1:49pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/1 "2006-01-01T13:49:05Z")
[IN this thread](http://boards.straightdope.com/sdmb/showthread.php?t=351917) 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. > [@Enola Straight](#): > > The salts and acids present in sweat would etch the glass and cause premature failure. As indicated [in the link below](http://www.tpub.com/content/photography/14209/css/14209_220.htm) 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. > [@](#): > > You should never touch a quartz-iodine lamp with your fingers. The oil from your hands can create a concentrated hot spot on the lamp, causing it to bubble and burn out Even halogen bulb [installers](http://www.aicautosite.com/garage/carcare/care17.asp) and [distributors caution](http://www.hafeleamericas.com/canada/support/faq.html#JS) against touching the bulb. > [@](#): > > Q: Why do they say not to touch the bulbs with your bare fingers? > A: Touching the bulbs with your bare fingers may cause premature failure of the bulb. Oils in your skin can cause hot spots on the glass envelope that will result in considerably shortening its life, and may even cause the bulb to burst. Salts in your sweat can also cause problems. This is true of other electronic items such as watch batteries and computer contacts. > [@](#): > > Be careful not get any of the dielectric grease onto the bulb. The bulb’s life will be shortened. Also whenever you replace a composite lamp, care must be taken not to touch the envelope with the fingers. Staining the bulb with normal skin oil can substantially shorten the life of the bulb. Handle the lamp only by its base. Also dispose of the old lamp properly. 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](http://www.homeownerschat.com/message128920-2.html) who appears authoritative, says the whole “don’t touch” warnings are urban legends. > [@](#): > > Unfortunately, so-called soft starting doesn’t help bulb life much – a few > hours at most – according to the data that I’ve seen. It’s more likely that you have some bad bulbs. I hope you replaced the failed bulbs with high-quality name brand bulbs. That’s the best way to ensure rated bulb life and at least you can complain with some hope of replacements if there is a problem. > > It’s an urban legend that bulb life of halogen lamps is shortened by finger oil. The surface of the bulb may degrade somewhat where dirt and oil react with the quartz; but that doesn’t affect bulb life only the appearance of the bulb. > TKM 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? ---
**Author:** ![Mr.Blue\_Sky](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@Mr.Blue\_Sky](https://boards.straightdope.com/u/Mr.Blue_Sky)\ **Post date:** [January 1, 2006, 2:38pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/2 "2006-01-01T14:38:19Z")
I’ve replaced the headlight bulbs in my car and the package says not to touch the glass part of the bulb. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 1, 2006, 2:46pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/3 "2006-01-01T14:46:56Z")
More explanations. The [traditional explanations](http://www.facilitiesnet.com/ms/article.asp?id=1699) with [additonal failure mechanism explanations](http://www.doc-imaging.com/halogen_lamps1.htm) > [@](#): > > Also, workers should take care not to touch the envelope of these bulbs or halogen bulbs because doing so leaves skin oils on the glass surface. As these bulbs heat and cool, the oils cause uneven stress, leading to glass cracking and shorter lamp life. > [@](#): > > Contamination – Contamination of the bulb can also reduce lamp life. Dust, oil from fingerprints, and other contaminants can all greatly reduce the efficiency and life of a halogen lamp. These contaminants often create “hot spots” – concentrations of heat energy – on the bulb’s surface. A hot spot can cause the tungsten filament to overheat, reducing the life of the filament and, consequently, the lamp itself. In addition, hot spots can lead to an imbalance in the halogen/tungsten mix, with the excess tungsten gas darkening the bulb prematurely. To avoid problems due to contamination, minimize direct contact with the bulb wall; halogen lamps should be wrapped in protective paper or held by the ceramic ends. Also, be sure to thoroughly clean the lamp before installation and during every service call. [We also have a “soft spot” hypothesis](http://www.interlight.biz/frequently_asked_questions.htm) > [@](#): > > Q. Why shouldn’t I touch the glass on a halogen bulb? A. Halogen lamps are made with Quartz glass. Oils from your hands cause a chemical reaction with the glass resulting in a “soft spot” in the glass envelope. Halogen lamps contain a tungsten filament manufactured under high pressure. The “soft spot” will bulge out or even erupt and explode, shattering glass and could cause personal injury. If you have accidentally touched your lamp, you can use alcohol or window cleaner containing alcohol to wipe off the fingerprints. Use cotton or latex gloves or a clean cloth when installing a new lamp. [One “soft spot” type explanation with failure mode pictures](http://www.donsbulbs.com/cgi-bin/r/t.pl/failures.html) > [@](#): > > Fingerprint: Oils from fingerprints and other contaminations on quartz bulbs causes divitrification chemical reaction when bulb is heated. Quartz glass crystallizes becoming brittle causing premature glass failure (bulb could explode.) Remove all contamination from glass before installing. So now we have three main hypotheses 1: Oil causes hot spots causing bulb overheating and messing up gas mixture 2: Oil causes hot spot thermal cycling stress compromising glass envelope integrity 2: Oil causes soft spots / de-vitrification compromising glass envelope integrity ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [January 1, 2006, 2:48pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/4 "2006-01-01T14:48:06Z")
- - - 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. ~ ---
**Author:** ![A.R.Cane](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@A.R.Cane](https://boards.straightdope.com/u/A.R.Cane)\ **Post date:** [January 1, 2006, 2:51pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/5 "2006-01-01T14:51:53Z")
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. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [January 1, 2006, 2:58pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/6 "2006-01-01T14:58:24Z")
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. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 1, 2006, 3:05pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/7 "2006-01-01T15:05:47Z")
> [@DougC](#): > > - > - > - 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. > ~ OK 4 hypotheses 1: Oil causes hot spots causing bulb overheating and messing up gas mixture 2: Oil causes hot spot thermal cycling stress compromising glass envelope integrity 3: Oil causes soft spots / de-vitrification compromising glass envelope integrity 4: Per DougC per falshlight bulbs - “Salt in the oil from your skin relfects too much heat back into the bulb” and causes near immediate bulb burnout. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [January 1, 2006, 3:16pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/8 "2006-01-01T15:16:08Z")
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. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 1, 2006, 3:24pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/9 "2006-01-01T15:24:55Z")
> [@Squink](#): > > 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. OK 5 hypotheses - 1: Oil causes hot spots causing bulb overheating and messing up gas mixture 2: Oil causes hot spot thermal cycling stress compromising glass envelope integrity 3: Oil causes soft spots / de-vitrification compromising glass envelope integrity 4: Salt in the oil from your skin reflects too much heat back into the bulb" and causes accelerated bulb burnout. 5: The “shadow” of hydrocarbon residue from the burned oil accelerates the natural progression of bulb shadowing and ultimate overheating failure ---
**Author:** ![NoCoolUserName](https://avatars.discourse-cdn.com/v4/letter/n/5fc32e/32.png) [@NoCoolUserName](https://boards.straightdope.com/u/NoCoolUserName)\ **Post date:** [January 1, 2006, 4:00pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/10 "2006-01-01T16:00:49Z")
Somebody call Myth Busters–this is right down their alley. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [January 1, 2006, 7:26pm UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/11 "2006-01-01T19:26:33Z")
> [@](#): > > 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. ---
**Author:** ![docandjean](https://avatars.discourse-cdn.com/v4/letter/d/7993a0/32.png) [@docandjean](https://boards.straightdope.com/u/docandjean)\ **Post date:** [January 2, 2006, 1:25am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/12 "2006-01-02T01:25:45Z")
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. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 2, 2006, 1:30am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/13 "2006-01-02T01:30:33Z")
> [@docandjean](#): > > Halogen lamps used in television lighting definitely do not like fingerprints. 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. ---
**Author:** ![racer72](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/racer72/32/3075_2.png) [@racer72](https://boards.straightdope.com/u/racer72)\ **Post date:** [January 2, 2006, 2:10am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/14 "2006-01-02T02:10:45Z")
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. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 2, 2006, 3:06am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/15 "2006-01-02T03:06:10Z")
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. ---
**Author:** ![even\_sven](https://avatars.discourse-cdn.com/v4/letter/e/dfb087/32.png) [@even\_sven](https://boards.straightdope.com/u/even_sven)\ **Post date:** [January 2, 2006, 4:33am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/16 "2006-01-02T04:33:03Z")
Film lights will explode if you touch them. As a film student working with inexperienced flunkies, this happened to me quite a lot. ---
**Author:** ![lissener](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lissener/32/6139_2.png) [@lissener](https://boards.straightdope.com/u/lissener)\ **Post date:** [January 2, 2006, 4:42am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/17 "2006-01-02T04:42:51Z")
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”?) ---
**Author:** ![MandaJo](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@MandaJo](https://boards.straightdope.com/u/MandaJo)\ **Post date:** [January 2, 2006, 4:44am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/18 "2006-01-02T04:44:19Z")
> [@Gary T](#): > > 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. 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. ---
**Author:** ![MandaJo](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@MandaJo](https://boards.straightdope.com/u/MandaJo)\ **Post date:** [January 2, 2006, 4:45am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/19 "2006-01-02T04:45:26Z")
> [@lissener](#): > > 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”?) I think myth implies there is more cultural signifigance to a story. ---
**Author:** ![MandaJo](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@MandaJo](https://boards.straightdope.com/u/MandaJo)\ **Post date:** [January 2, 2006, 4:48am UTC](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951/20 "2006-01-02T04:48:30Z")
> [@lissener](#): > > 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”?) I think myth implies more cultural signifigance to a story. [Next page](https://boards.straightdope.com/t/touching-halogen-bulb-causes-premature-failure-urban-legend-or-not/337951.md?page=2)