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How fast does beer skunk, in the bottle or out? I have heard people claim their IPA gets skunky in the glass as they drink it on the sunny patio.

I have also left a sixer of beer on a shelf on my porch in the shade after shopping say, only to come back later to grab it and the shifting sun/shadows is now shining on the beer. How fast does that process take to skunk beer.

What's peoples experience with this?

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Would you consider changing one of the tags to light-struck? Maybe storage or packaging? –  Dean Brundage Feb 24 '10 at 21:44
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1 Answer

up vote 10 down vote accepted

In short, it depends.

The April 10th, 2008 episode of Basic Brewing Radio is all about glass and skunking.

How Fast?

Unprotected beer will rapidly skunk. I had a keg of blonde ale in the sun one summer afternoon. The beer in the three feet of tubing spoiled in less than a minute. The small volume of skunky beer was strong enough to ruin an entire pint. It was a light beer unprotected from the sun. Dark beer in brown bottles are fairly well protected from skunking wavelengths and will spoil more slowly.

Background

Skunking is caused by a wavelength of light (350–520 nm BYO) emitted by the sun and florescent lights. Incandescent lights do not produce light in that range. The more light of these wavelengths that strikes your beer the quicker skunking reactions occur.

Colored bottles absorb & reflect wavelengths of light Wikipedia. Green & blue bottles do not absorb the whole range of skunking light making them inferior protectors. Brown bottles absorb the high frequency wavelengths and are pigmented with iron oxides. These various forms of iron absorb UV light over a wide spectrum of wavelengths.

Like bottles, beer also absorb light. Dark brown beers afford a stronger barrier protecting the liquid further inside the bottle. Light beers, like IPAs, are more susceptible to skunking.

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Incandescent bulbs DO produce in the skunking range of wavelengths, but the intensity is about a third to a half that of sunlight or UV bulbs, so the skunking doesn't happen as fast. –  drj Mar 17 '11 at 7:15
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