No; you’re thinking of “legend.” No one would ever say “Water goes down the drain in different directions on different sides of the Equator? That’s a legend.” But they would say, “–that’s a myth.” (See definition #4.)
“Myth” is frequently used figuratively, to describe something that’s widely believed but untrue. Only, not any more; nowadays people say “urban legend.”
Dude, the manufacturer of the product instructing you how to use that product is hardly comparable to schools spreading third-party rumors.
It seems pretty comperable to hospitals warning about needles in Halloween candy: one would assume they’d be in a position to know.
It appears you’ve overly focused on “official.” To expand on what lissener said, it’s not simply that they’re an official source, but that this is what they do. It’s their area of expertise. They designed the product, they tested the product, they know the product, and they know what they’re talking about.
One would assume wrong. Now, if they had ever actually experienced the phenomenon, and reported the facts about it, yeah they’d be in a position to know. But they were merely passing on unsubstantiated rumors about something that they really didn’t know about. Unless you’re maintaining that manufacturers of halogen bulbs don’t have any knowledge of the products they produce, it’s an apples and oranges comparison.
I don’t think you can assume that he makers of hallogen bulbs actually did “the finger test” and proved that there was a reduction in bulb life. I’m not saying there’s not: there may very well be. I’m just saying that manufacters are not always perfectly authoritative sources on their products: if “everyone knows” that fingerprints reduce bulb life, I find it perfectly plausible that they might put the warning on the box without testing it. After all, even if it isn’t true, it isn’t going to cost them anything, and might forstall people calling to complain how they ruined their bulb because they didn’t know not to touch it.
I deal with slide projectors quite a bit and in my anecdotal experience if you touch one of those bulbs while installing it will blow out quite quickly, so you need to use a handkerchief or something (like, going through 3 bulbs in a 50 minute period, rather than one over 4 months). I suspect finger oil makes bits overheat.
Wow. You’re really gonna go to the mat to defend this?
I see his point…I make stuff and I sell the same stuff. I’m not PERFECTLY authoritative on all the details. There are some aspects of manufacturing and use that I haven’t personally proven are true, or that I have seen research actually done to prove it to be true…We/I have been told at some point by someone(s) that these aspects could be true, and we take it for granted. When someone asks, I repeat what I’ve been told because it makes sense and it MAY prevent failure or mis-use.
Just because “everyone” (including the manufacturer) knows it to be true, doesn’t unerringly mean to be so…
lissener, can I suggest a book of short stories called “The Periodic Table” by Primo Levi to you? Read a story in it called, ummm, actually I can’t remember the name and I’ve just remembered that I lent my copy to my father. Read the whole damn thing, all the stories in it are pretty much masterpieces, but I think the one I’m thinking of is called “Chromate”. It’s the one about orange paint, anyway.
Another one you might want to read is called “The Sleepwalkers” by Arthur Koestler.
Experts ain’t necessarily experts.
That’s the crux of the matter…did they (or someone) actually test the product with respect to touching vs. not touching. Seeing some empirical evidence should shed light ( 
)on the issue.
And maybe its inconclusive; such that certain brands, or older designs will fail, but others won’t.
Not light bulbs, but closde – I used to grow crystals in crucibles of various materials. When I used fused silica crucibles, I found that after I retrieved them from the furnace they had my fingerprints etched in the sides. Undoubtedly due to stuff from my fingertips getting on the silica. I suspect mainly the salts, but it could be oils instead, or as well. In any case, touching silica witgh your bare hands before heating to extremely high temperatures (which tungsten halogen bulbs require in order to work efficiently) is clearly contraindicated – the etching weakens the silica or glass. After that, I wore gloves. Then I switched to different crucible materials.
We have ample testimony that halogen bulbs fail prematurely if the glass is contaminated by residue from bare fingers. It’s a fact that it happens.
I first started using halogen bulbs in the 70’s. The instructions warned against touching them with bare fingers. At the time, most people had no idea what a halogen bulb was and you didn’t hear them being talked about in other than certain technical arenas.
This is the opposite of how urban legends are transmitted. They are typically widely spread through informal sources, usually with untraceable origins. They are seldom if ever found in technical literature.
So you have something that is true that has been in relatively obscure technical sources for decades. With the increasing popularity of halogen bulbs, it has entered everyday conversation in perhaps the last ten years or so. We have so far one source calling it an urban legend.
I maintain he’s full of crap. It’s not an urban legend. No one else is calling it that. It doesn’t fit have any of the common traits of urban legends in origin, transmission, or style. We wouldn’t even be having this discussion if not for a solitary misguided statement. The guy is misusing the phrase “urban legend” because he apparently doesn’t know what their characteristics are. That one might construe a scenario in which an urban legend might find its way into manufacturer’s instructions (which I find dubious) doesn’t alter the fact that this piece of information is simply not an urban legend.
I think that there is enough practical experience related in this thread that we can safely say that touching a bulb with your bare hands during the installation is a bad idea and will cause premature failure. If you still are not sure, feel free to go buy two halogen bulbs. Touch one and install it. Turn it on and start timing. After it fails repeat with the second one, only this time do it right. After your bulb has passed the failure point of the first bulb you have proved that this is no myth.
Me, I will take the word of the bulb maker since he knows more about this subject than I do.
From researchers at Michigan State:
Halogen bulbs burn much brighter and produce much more heat than standard incandescent bulbs.
When you touch one of these bulbs (never touch a light bulb while it is on), oil from your skin leaves a residue on the glass shell to the bulb. When the bulb is turned on, it begins to get hot. Much of this heat is dumped into the air around the bulb and is carried away.
However, when there is oil on the bulb, it begins to get heated as well. The heat is actually enough to cause the oil to boil and its temperature can reach near 1,100 degrees Fahrenheit.
This “hot spot” puts a great deal of heat near the glass bulb and can cause the glass in the hot spot to warp and stretch. This causes a weak spot in the glass bulb which can break and thus shorten the life time.
This is a newspaper article and simply repeats the warnings mentioned earlier re the “oil creates hotspot > glass stress” hypothesis. Have there been any scientific tests of this “fingerprint” failure mode? As much money as halogen bubs cost and given the large (and profitable) dollar market they represent for manufacturers I can’t believe there’s not some hard research on this somewhere.
I should have put this in the previous message -
My main problem with this “boiling oil” scenario is that I have several powerful halogen floor lamps and I know how hot they get, and that the “heat up” is almost instantaneous.
Let’s say we accept for argument’'s sake that “touching” harms the bulb in some way. I have difficulty considering that a near molecule thin layer of skin oil is going to “bubble” to the extent it begins to devitrify the glass bulb. I would imagine it would be flashed into a hydrocarbon reside within microseconds of the filament turning on. There may be thermal stress due to the dark/light hydrocarbon residue section it leaves on the glass absorbing more heat than the surrounding area, especially over time through numerous on-off cycles, but on a practical physical level this “boiling oil” hypothesis sounds a bit questionable to me. I don’t think there’s enough “oil” there to “boil”.
The only think I am defending is that a manufacturer’s warning label, especially on a non-FDA regulated product, is not so authoritative as to remove an issue from any possible skeptical inquirey. I really don’t see that as such a radical proposition.
I have no dog in this fight. I just don’t think that “Cuz the label says so” should be a discussion stopper.
See my post above. Fused silica crucibles are essentially the same material used to jacket those bulbs. After a single use my fingerpruints were etched in – direct personal experience, not speculation. I don’t know if oil or salts or both responsible, but something was. After repeated uses, the etching appeared to get worse. Anything that etches glass isn’t good for its structural integrity, especially if repeated uses make it worse.
You want to test this with bulbs? Get a fresh halogen bulb, handle it all over, and run it for a week or so. Take it out and examine it. I’ll bet you get etch marks.
So I’m clear by “etching” you mean actual physical grooves in the glass mimicking your fingerprints, not carbon shadows of hydrolyzed oil residue?
I’ve never heard of anyone using “etching” to mean burned residue – It always means that something has bitten into a surface. The resulting surface typically doesn’t look as if neat grooves have been eaten into it, but as if the surface has been “frosted”. It takes on a diffuse appearance. This is what happens with etching – it doesn’t proceed with equal speed everywhere on the glass surface. I’ve seen the same effect with glass treated with hydrofluoric acid or ammonium bifluorite.