# Question about quarts halogen light bulbs
**URL:** https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279
**Category:** Factual Questions
**Created:** [May 5, 2003, 10:23pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279 "2003-05-05T22:23:34Z")
**Posts on this page:** 17
**Page:** 1
### Author:  [@MrTuffPaws](https://boards.straightdope.com/u/MrTuffPaws)
#### Post date: [May 5, 2003, 10:23pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/1 "2003-05-05T22:23:34Z")
Do quarts halogen bulbs lose their light output over time?
About 3 years ago I bought a halogen floor lamp. The kind that shines directly upward and lights the room by reflecting light off of the ceiling.
When I first turned it on, it was like the sun its self came to be in my living room. Thanks be that it had a dimmer setting.
Now, 3 years later, it produces about as much light as a 60 watt incandescent bulb when on high. Now, I am pretty certain that I am not going blind, and I did tilt the lamp over and dust the reflector to no avail.
Has anyone else had this happen to them? Is it new bulb time, or new lamp time?
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### Author:  [@sailor](https://boards.straightdope.com/u/sailor)
#### Post date: [May 5, 2003, 10:33pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/2 "2003-05-05T22:33:45Z")
The problem may be with the dimmer rather than the bulb
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### Author:  [@MrTuffPaws](https://boards.straightdope.com/u/MrTuffPaws)
#### Post date: [May 5, 2003, 10:54pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/3 "2003-05-05T22:54:01Z")
I would think that to, but the lamp does not have a dimmer. It has 3 switch positions, high, low, and off. All work, and “off” works the best.
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [May 5, 2003, 11:00pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/4 "2003-05-05T23:00:32Z")
Sounds like the dimmer to me too. Try replacing the bulb, and if the problem remains, it’s likely time for a new lamp. At least you’ll have an extra bulb, if you should ever need one.
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### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [May 5, 2003, 11:10pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/5 "2003-05-05T23:10:35Z")
I agree it’s probably the dimmer, but if that fails you might try some quart **z** halogen bulbs. The quarts ones are probably the wrong size. 😃
::: Ducks and runs :::
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [May 6, 2003, 12:25am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/6 "2003-05-06T00:25:28Z")
Halogen lamps can dim with age. The quartz glass and halogen gases inside help to “recycle” the filament back onto itself as it burns off rather than simply building up on the inside of the glass. Eventually, it looses effectiveness.(There’s some pretty funky physics going on in those things)
Another possibility is the connections are corroding a bit and power is being lost there.
Finally, just because it’s not a continuous adjustment, doesn’t mean it’s not a dimmer. If you can readily get at the wiring, try bypassing it and see if things brighten.
And, whatever you do, never let your skin contact the glass bodies of quartz halogen lamps. The skin oils will react with the quartz at the high heat the things operate at, and at best, the glass will sort of bubble out where you touched it, or at worst, shatter. Having a 150-watt home lamp pop is festive, but a 1000-watt theatrical lamp go is rather dramatic.
There’s a reason theater and television people look down and close their eyes when they hear a ‘pop’ from above…
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [May 6, 2003, 12:33am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/7 "2003-05-06T00:33:07Z")
What happens is as the tungsten evaporates off the filament it combines with the halogen to form a tunsten halide, which prevents the tungsten from being deposited on the glass. When a tungsten halide molecule strikes the filament, it dissociates into free tungsten which is redoposied on the filament, and the halogen, which is then free to combine with a new evaporated tunsgten atom. The problem is, the filament is not equally hot across its length, so the rates of evaporation and redeposition are unequal. The tungsten evaporates faster on hotter portions of the filament, and gets redeposited faster on cooler parts. So, the hot parts get thinner and the cool parts get thicker, until the filament overheats at the thinnest point and fuses.
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [May 6, 2003, 4:45am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/8 "2003-05-06T04:45:07Z")
> [@](#):
>
> \*Originally posted by Q.E.D. \*
> \*\*What happens is as the tungsten evaporates off the filament it combines with the halogen to form a tunsten halide, which prevents the tungsten from being deposited on the glass. When a tungsten halide molecule strikes the filament, it dissociates into free tungsten which is redoposied on the filament, and the halogen, which is then free to combine with a new evaporated tunsgten atom. The problem is, the filament is not equally hot across its length, so the rates of evaporation and redeposition are unequal. The tungsten evaporates faster on hotter portions of the filament, and gets redeposited faster on cooler parts. So, the hot parts get thinner and the cool parts get thicker, until the filament overheats at the thinnest point and fuses. \*\*
I **told** you it was funky! 🆒
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### Author:  [@MummyCave](https://boards.straightdope.com/u/MummyCave)
#### Post date: [May 6, 2003, 12:52pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/9 "2003-05-06T12:52:25Z")
Q.E.D., your post show a lot of knowledge and insight in various topics of physics, especially in the every day area. I have learned a lot from your posts.
Unfortunately this time you got it just wrong. Perhaps because it is a chemistry question?
The process running in a halogen bulb is called a “transport reaction”: A chemical reaction between a solid and a gas generates a new gaseous compound. The later is able to travel to a different point which shows different conditions and cause the reaction to run reverse. So the solid is deposited again, the gas is free for another round.
The trick with halogens, e.g. chlorine, and tungsten is, they react at cooler places to form the gas WCL6. This falls apart at hotter spots.
As in every light bulb the filament evaporates tungsten atoms which settle eventually down at the cool glass walls of the bulb. There the are picked up by the halogen and deposited preferably at the hottest spot around. This will be the thinnest part of the filament increasing its diameter again.
The filament in a halogen bulb is self-healing.
(Traces of water, for example, would work in the opposite direction and carry away material from the hottest/thinnest part of the filament.)
As a result you can make filaments in halogen lamps thinner from the beginning, making them hotter and increase the output ratio of visible light over infrared, reduce the amount of wasted heat.
The visible light output is nearly twice that of a standard bulb at the same watts input.
Old standard light bulbs develop a layer of tungsten metal on the inside and that will obviously block escaping light. Often you can see blackened spots with the naked eye.
This never happens in a halogen bulb.
MrTuffPaws, I never experienced what you do, nor heard about that. For me the halogens just die some day.
I would like to support gotpasswords idea about corroding contacts, either on the outside of the bulb or ,more probably, at the lamp itself. The greater heat supports faster corrosion.
MrTuffPaws, go and check, perhaps some sandpaper helps.
MummyCave
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### Author:  [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)
#### Post date: [May 6, 2003, 1:51pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/10 "2003-05-06T13:51:26Z")
Everything you wanted to know about [Halogen](http://www.lighttrader.com/ResourceGuides/HalogenIncandescentLamps.htm) light bulbs.
I suspect some of you got your info from this site…
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### Author:  [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)
#### Post date: [May 6, 2003, 1:59pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/11 "2003-05-06T13:59:17Z")
By the way, ALL lamps will dim with age. Halogens are so bright that the dimming from age is harder to notice.
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### Author:  [@MummyCave](https://boards.straightdope.com/u/MummyCave)
#### Post date: [May 7, 2003, 8:05am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/12 "2003-05-07T08:05:11Z")
Quote:
I suspect some of you got your info from this site…
Quote
No, I didn`t. It’s just a spin off of my masters in chemistry.
What about that remark anyhow, you want to accuse us of chaeting ?
MummyCave
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### Author:  [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)
#### Post date: [May 7, 2003, 8:18am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/13 "2003-05-07T08:18:51Z")
I read through **whuckfistle** ’s citation, **MummyCave** , and there’s just no way **whuckfistle** was saying that was where _your_ information came from. 🙂
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### Author:  [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)
#### Post date: [May 7, 2003, 10:31am UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/14 "2003-05-07T10:31:29Z")
> [@](#):
>
> \*Originally posted by MummyCave \*
> \*\*Quote:
>
> I suspect some of you got your info from this site…
>
> Quote
>
> No, I didn`t. It’s just a spin off of my masters in chemistry.
>
> What about that remark anyhow, you want to accuse us of chaeting ?
>
> MummyCave \*\*
That was tongue in cheek, **MummyCave**. Don`t be offended, most of the time someone will ask for a site anyway. I just made it easier on you.😉
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### Author:  [@MummyCave](https://boards.straightdope.com/u/MummyCave)
#### Post date: [May 7, 2003, 3:52pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/15 "2003-05-07T15:52:53Z")
Accepted.
I’ll try to be less jumpy next time, but I did not realize the tongue in cheek intention.
Myself, I am not so good at finding usable sites.
Actually I had been looking for one and didn’t succed.
whuckfistle, yours is a good one, giving a lot of technical details, and I bookmarked it for thorough reading some time.
MummyCave
However, as far as I saw so far, the chemestry question is not covered there.
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### Author:  [@bernse](https://boards.straightdope.com/u/bernse)
#### Post date: [May 7, 2003, 4:01pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/16 "2003-05-07T16:01:42Z")
FWIW: I have the same lamp by the sounds of it. I can buy a brand new lamp for the price of a 2-pack of those bulbs.
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### Author:  [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)
#### Post date: [May 7, 2003, 5:37pm UTC](https://boards.straightdope.com/t/question-about-quarts-halogen-light-bulbs/173279/17 "2003-05-07T17:37:28Z")
> [@](#):
>
> \*Originally posted by bernse \*
> \*\*FWIW: I have the same lamp by the sounds of it. I can buy a brand new lamp for the price of a 2-pack of those bulbs. \*\*
Same with stinkin` printers. With some models, a couple of ink cartridges cost the same as a new printer.