Fluorescent lights skunking brew

I've not tested yet how long it takes a fluorescent light to skunk beer but since beer will skunk with any wavelengths of light below 500 nm I know it will happen eventually.

My new brew room has fluorescent lights in it and I like them for their energy efficiency (and they already are there instead of having to install something new). So I looked into either bulbs that don't emit below 500nm or protective guards that block UV. I've found that you can buy amber guards that will block all wavelengths below 500nm, they are sometimes marketed as bug lights. (McMaster has some)

So just thought I'd inform those that want to use fluorescent lights (including CFL bulbs) to get the bug light variety or the amber guards.

conpewter said:

I've not tested yet how long it takes a fluorescent light to skunk beer but since beer will skunk with any wavelengths of light below 500 nm I know it will happen eventually.

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It would like to see such data. I have an UV lamp and I wonder if I could use it for a hopped wort, to kill some bugs before I pitch the yeast. How long could I light it before skunking effect takes place.

I'll try to find the reference.
IIRC skunking occurs in a few minutes under direct sunlight.
Or in about an hour under fluorescent light.
Incandescent light takes much, much longer.
Don't know about Halogen or LED, but they are bluer (less yellow?)
than incandescent, so I'd treat them like fluorescent.

I would not use a UV light on beer or wort.
I think it would be good to use on work surfaces and utensils,
but I don't have anything to back that up.

IMHO, its overkill. Spray your fermenter and hoses with StarSan, then RDWHAHB.

Found the 500 nm reference on this page
houblon.net - "A Skunk Walks into a Bar..."

Data about bug lights

Yellow fluorescent lights: The spectrum is nearly identical to a normal fluorescent bulb except for a near total lack of light below 500 nanometers. This effect can be achieved through either specialized phosphor use or more commonly by the use of a simple yellow light filter. These lamps are commonly used as lighting for photolithography work in cleanrooms and as "bug repellant" outdoor lighting (the efficacy of which is questionable).

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fluorescent lamp: Definition from Answers.com

I agree it may be overkill but if beer will skunk in 1 hour under fluorescent and I have a fluorescent light in my brew room then the wort is hopped under that light for more than an hour depending on boil time of course

Ok so I read that webpage again, thinking more about my setup and I think I know why I don't get skunked beer if I boil outside in direct sunlight and transfer cool wort into clear carboys in sunlight.

Riboflavin, a compound produced by yeast during fermentation, absorbs energy from light at wavelengths of 350 to 500 nanometers (nm). It transfers the energy to iso-alpha acids, the compounds that give beer bitterness. They then release free radicals-small, unstable chemical fragments-that react with sulfur compounds produced by the yeast. The result is the offending thiol.

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So no riboflavin, then no skunkyness which means you can't skunk beer until after fermentation has started. So I really only need to worry about the lights in my brewing room (Even then the beer is in the fermentation freezer not sitting under the light)

I once experimented with the leftover wort from my hydro reading (only lightly hopped, a hefe) using a small UV florescent about 2 inches away it took about 30 seconds to skunk the wort, but this was a blacklight in close proximity so it doesnt tell you much about normal florescents except that IF they give off a fair amount of UV it wont take long to skunk a beer.

You can't just come up with a quick and dirty rule of thumb. Its going to depend on the original intensity of the light source, the distance of the source from the target, the pigmentation of the target (a darker beer will absorb more light at its interface surface than a lighter colour beer) and the thickness of the target (light will be absorbed only near the surface of the carboy and be significantly attenuated within about 1mm). If you run a test in a shallow vessle then you expose most of the available target to light vs. running a test in a deep vessle.

Thank you for your input. I didn't expect skunking effect comes so fast, I taught it would be hours, not minutes.
Conclusion - no posiibility of UV sanitation of ready-to-pitch wort. Pity

I brew outside in the sun often. How come the sun doesn't skunk my beer up?

I put my fermenters under boxes...

mysteryberto said:

I brew outside in the sun often. How come the sun doesn't skunk my beer up?

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Riboflavin, a compound produced by yeast during fermentation, absorbs energy from light at wavelengths of 350 to 500 nanometers (nm). It transfers the energy to iso-alpha acids, the compounds that give beer bitterness. They then release free radicals-small, unstable chemical fragments-that react with sulfur compounds produced by the yeast.

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Since Riboflavin is made by the yeast and that is the first step in skunking the beer you can't skunk beer until it has started fermentation. So while you are brewing sunlight doesn't matter. You can put it under UV light all you want until it has started fermentation.

giligson said:

.... the thickness of the target (light will be absorbed only near the surface of the carboy and be significantly attenuated within about 1mm).

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That's probably the main thing that protects you when you are brewing. Not much surface is exposed in the kettle.

Even so, my carboys are all wearing old t-shirts, just to be safe.

I guess I wont throw all those old shirts out now...




it lives...

Piotr said:

Thank you for your input. I didn't expect skunking effect comes so fast, I taught it would be hours, not minutes.
Conclusion - no posiibility of UV sanitation of ready-to-pitch wort. Pity

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mysteryberto said:

I brew outside in the sun often. How come the sun doesn't skunk my beer up?

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Both of you guys read what was posted again...

Skunking is something that happens POST-fermentation. There are compounds that are absent in our wort that is not yet beer. Once you have started to ferment, all bets are off. And yeah, a beer will start to skunk in a matter of seconds. Even in an amber bottle, you don't want to have too much direct sunlight. I've had a bottle of SNPA that was left to the sun for a few hours that was super skunked.

I keep my carboys covered with a towel and in the fermentation area I just have 1 25 watt bulb on a pullchain.

No CFL's for me here; they're not dimmable, they contain mercury, which poisons the air if they break (http://www.energystar.gov/ia/products/lighting/cfls/downloads/CFL_Cleanup_and_Disposal.pdf), and they are a disposal hazzard (can't just throw them in the trash).

Brewdouche-RuBrew said:

I guess I wont throw all those old shirts out now...

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Seriousy. Works great, cheap and disposable as well.

Of course, your carboys clothing should be appropriate...