incan spectrum

Lots of info and posts about various LED spectral ouput, but I've been taking for granted what the spectrum of an incandescent tungsten filiment is. "It's just like the sun!" But is it?

What I am curious about is the UV, and very specifically, if there is UV, is there germicidal UV-C 254nm output? Enough to sanitize like a mercury vapor lamp (that conveniently and coincidentally outputs light close to that range, which is ideal for germicidal purposes)?

Well, I know the filiment is surrounded by a glass globe, and there is also the glass flashlight lens, so the light must pass through at least 2 clear glass "filters."

There is an anacdote about world famous physicist Richard Feynman's presence at the Trinity Experiment. This story is how I first learned that UV doesn't go through glass. Feynman had so much faith in his physics that he sat in his truck during the detonation, and did not wear the dark UV-blocking goggles that were distributed to the witnesses.

What I see in online searches are the token spectral graphs for incandescent light. They're pretty generic. Has anyone tested the spectral output from, specifically, a Surefire incan? Maglite? I know some lucky CPF members have spectral analyzers.

Has anyone looked specifically at the incan flashlight spectum?

Was Feynman wrong? Is any UV-C escaping through the globe and the lens? Enough to zap microbes and ensure the water you're about to drink will not induce Montezuma's Revenge?

Here are measured spectra of halogen bulbs at 2000h and 300h life expectancy. The key thing here is the shift to shorter wavelengths at shorter runtimes.

The bulbs in Surefire lights have a life expectancy of around 50h, so there will be more short wavelength radiation. Here is the spectrum of the Surefire A2 which is a regulated light with a low-wattage bulb. More can be found here.

I din't think incan emit a meaningful amount of UV-C.

The_Driver said:

Here are measured spectra of halogen bulbs at 2000h and 300h life expectancy. The key thing here is the shift to shorter wavelengths at shorter runtimes.

The bulbs in Surefire lights have a life expectancy of around 50h, so there will be more short wavelength radiation. Here is the spectrum of the Surefire A2 which is a regulated light with a low-wattage bulb. More can be found here.

I din't think incan emit a meaningful amount of UV-C.

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Thank you!

I've been thinking about this for a while, but probably wrong-headed. A Surefire flashlight, beyond it's near best-possible incan utility, is obstensibly a weapon, the light itself, the photons. If you didn't want to kill something or someone, or a bunch of things, blinding them is the featured alternative, but also with UV, not just temporary blindness from white intensity, but permanent retinal damage from invisible UV. I'm not endorsing this, it's not what I would use it for, not a soldier or cop, but sometimes there is hidden unadvertised functionality in goverment tools, such as flash-sanitizing the surface of a wound, or encouraging stages of permanent blindness in an enemy. Intended or happy accident?

I am disappointed by the graphs, and at the same time encourged by your interpretation. Appears to me that glass is doing mostly what Mr. Feynman knew it would, but not entirely, just almost entirely.

Why didn't you think incan would emit UV-C? I hoped it would, assumed that an naked filament does, and then discovered UV is filtered by glass, which is probably a good thing considering the stretch of history for incan lighting compared to how long it took to discover how what can't be seen can cause permanent blindness.

I think to do what I like to do, use flashlight to instantly sanitize, I would need a smallish bipin 3V-9V Deuterium lamp (or Mercury vapor (fat chance)) that would fit Tad Customs' E-socket, or a 5mm LED that humps its bell curve at 254nm, but perhaps the 50 hour Surefire lamps will, if not instantaneously, do microbes in after a long exposure.

OP, please remain aware of Rule 11 ...

You agree, through your use of this BB, that you will not post any material ... which promotes activity that ... could reasonably be foreseen to threaten any person's safety.

No more on "intentional blinding" , thanks

Here's a spectrum and CRI data for a 60W incan. Pretty much a perfect match for a black body radiator.

maukka said:

Here's a spectrum and CRI data for a 60W incan....

Click to expand...

Beautiful, isn't it ...

maukka said:

Here's a spectrum and CRI data for a 60W incan. Pretty much a perfect match for a black body radiator.

Click to expand...

Yeah, its a great little black body radiator. Again the spectral curve shows the UV end is different from the sun, perhaps due to glass filtering UV. I think we would not want residential incan lighting to have too much or any UV, germicidal or otherwise.

Fivemega needs to chime in here. And Dano... that would be cool.

@Maukka: 2600K is pretty low, I'm guessing is not a halogen, but a normal incan bulb?

@night.hoodie have you thought about what type of glass these bulbs use? Normal household an xenon halogen bulbs (at least those from Osram) have quartz glass which is doped to filter the UV radiation. Quartz glass is needed because it tolerates heat better than all other kinds of glass (lowest rate of expansion). I'm note sure if the Surefire biulbs also use quartz or maybe just borosilicate?

You could also ask Mark from Lumensfactory what kind of glass he uses. Maybe he can make you a bulb with undoped quartz glass.

Some UV makes it through glass, we know that because drapes, etc,... pigments fade over time from sunlight, even through glass.

Apparently it's UVA that's making it through glass, while UVB is mostly blocked... he might well have been in a car with glass that he'd researched, that had UVA filters.
He was a smart guy, and understood the problems with assumptions.

Some types of halogen lamp DO emit enough UV for this to be a potential health hazard. The packaging of such lamps carries a warning that they should only be used in enclosed fixtures, such that the cover glass will block the UV output.
The quartz used in the manufacture of many types of halogen lamp is transparent to UV unlike regular window glass which substantially blocks UV.
The quartz can be doped during manufacture so as to block the UV, and this is done in the case of "UV stop" lamps that are approved for use in open fixtures.

The UV from a halogen lamp that is intended for an enclosed fixture, but that is incorrectly used in an open fixture, is unlikely to be dangerous but could be in extreme circumstance, such as prolonged exposure improbably close to the lamp.

There used to be a type of halogen lamp optimised for UV output, it was used for the curing of resin used in dental work, now largely replaced by short wavelength, high power LEDs.

I doubt that any halogen flashlight bulb produces significant UV output

night.hoodie said:

I've been thinking about this for a while, but probably wrong-headed. A Surefire flashlight, beyond it's near best-possible incan utility, is obstensibly a weapon, the light itself, the photons. <snip>

I am disappointed by the graphs, and at the same time encourged by your interpretation. Appears to me that glass is doing mostly what Mr. Feynman knew it would, but not entirely, just almost entirely.

Why didn't you think incan would emit UV-C? I hoped it would, assumed that an naked filament does, and then discovered UV is filtered by glass, which is probably a good thing considering the stretch of history for incan lighting compared to how long it took to discover how what can't be seen can cause permanent blindness.

I think to do what I like to do, use flashlight to instantly sanitize, I would need a smallish bipin 3V-9V Deuterium lamp (or Mercury vapor (fat chance)) that would fit Tad Customs' E-socket, or a 5mm LED that humps its bell curve at 254nm, but perhaps the 50 hour Surefire lamps will, if not instantaneously, do microbes in after a long exposure.

Click to expand...

I like the way your brain works.. I have this categorized in my head under "My Random Thoughts" for sure.

broadgage said:

Some types of halogen lamp DO emit enough UV for this to be a potential health hazard. The packaging of such lamps carries a warning that they should only be used in enclosed fixtures, such that the cover glass will block the UV output.

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Since Incan light bulbs have been banned and LED (obviously) have taken their place, the closest alternative (forget CFL) that I see offered these days are Halogen bulbs enclosed inside an Incan looking globe (heck, many people probably can't even tell the difference).

Anyway, I prefer to use these in fixtures such a bathroom mirrors/vanity's to get the closest I can to "Natural" lighting. When I first purchased a pack I noticed a warning on the package that stated something along the lines of, "Do Not Use If Outside Glass Is Broken". Makes me think that these are non-UV coated bulbs that rely on the traditional looking bulb glass to provide the UV blocking. Technically if only the outside glass broke on these bulbs, the Halogen bulb inside will continue to operate normally as long as it remained in the socket.

Wonder if they're a tad cheaper to make with the non-UV protected Halogen bulbs.....

1pt21 said:

When I first purchased a pack I noticed a warning on the package that stated something along the lines of, "Do Not Use If Outside Glass Is Broken". Makes me think that these are non-UV coated bulbs that rely on the traditional looking bulb glass to provide the UV blocking. Technically if only the outside glass broke on these bulbs, the Halogen bulb inside will continue to operate normally as long as it remained in the socket.

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UV is not the reason for this.
All halogen bulbs must be used inside a fixture which prevents pieces of glass flying around when a bulbs bursts/explodes. There is always a small risk of such a lamp exploding. Improper handling (without a cloth or gloves or wiping it down with alcohol) is the main reason why such bulbs explode. Fat residue (fingerprints) from your hand on the bulb will cause uneven temperature distribution which in turn increases the thermal stress of the glass. It will weaken in time and can then explode.

The_Driver said:

UV is not the reason for this.
All halogen bulbs must be used inside a fixture which prevents pieces of glass flying around when a bulbs bursts/explodes. There is always a small risk of such a lamp exploding. Improper handling (without a cloth or gloves or wiping it down with alcohol) is the main reason why such bulbs explode. Fat residue (fingerprints) from your hand on the bulb will cause uneven temperature distribution which in turn increases the thermal stress of the glass. It will weaken in time and can then explode.

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Interesting! Your explanation makes perfect sense, thanks for the reply :thumbsup:

The_Driver said:

@night.hoodie have you thought about what type of glass these bulbs use? Normal household an xenon halogen bulbs (at least those from Osram) have quartz glass which is doped to filter the UV radiation. Quartz glass is needed because it tolerates heat better than all other kinds of glass (lowest rate of expansion). I'm note sure if the Surefire biulbs also use quartz or maybe just borosilicate?

You could also ask Mark from Lumensfactory what kind of glass he uses. Maybe he can make you a bulb with undoped quartz glass.

Click to expand...

Well, contributions to this thread already made me realize, unless it was already the case that UV seeps out, I wouldn't want to use a lamp that put out sanitizing amounts of UV, because it is dangerous, a light you can't see that will blind (sorry mods). If it was there already, cool, I'll zap all my drinking water beforehand, and start being more careful, but otherwise, glad it isn't (much, if at all) there.

If I want antimicrobial UV, though the powerLED variety of 254nm output is outrageously expensive, hundreds of dollars for one LED, the 5mm variety in that spectral range, though not as tight a curve, costs pennies. 5mm LED can be trimmed and sculpted easily to fit in Tad Customs E-socket, so I can go that route if I want an E-series sanitizer (after first finding one that has the right voltage/amperage specs and matching to appropriate cells). To ask Mark for undoped quartz lamps is kind of outrageous considering the extant and wildly cheap 5mm UV-C LEDs, because I don't need it to throw more than inches.

If you wish to sterilise drinking water with ultraviolet light, equipment is available to do this.
A hand held battery operated light is available to treat water in a cup or glass, to avoid eye or skin damage it is equipped with an interlock to prevent operation unless immersed.

Larger units intended to treat the water to a home are plumbed in and pass the water around ultra violet lamps.