When does light become a problem?

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Senior Member
Sep 1, 2008
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I know sunlight and fluorescent light are supposed to be bad for wine, but mostly you hear about it in conjunction with aging. Does anyone understand the danger the light poses enough to tell me at what stage it becomes a problem and why?
From what I understand, light generally effects wine in 2 ways that can be a problem. Infrared/heat from sunlight contributes to the oxidation of wine, and destroys delicate compounds/esters within the wine that give it bouquet and flavor. Also microbes that produce off-flavors are encouraged, that would normally not succeed in growing in a cool/dark atmosphere. Another way that wine can be damaged is with strong fluorescent light, where budding yeast cells are inhibited from growth due to the ultraviolet rays present, which reduces the quality/vigor of the fermentation. It is certainly OK, to inspect your wine with moderate incandescent light or even a flashlight to see how fermentation is progressing and also to inspect lees/deposits in your fermentaton vessel, and also to see how clear the wine is.
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The only time light becomes a problem is if it's for a lengthy period of time. You don't want your carboy in a well lit room, near a window, or on the average kitchen counter. If you don't have a dark room (like a closet) that's appropriate, just cover it up. I wrap my carboys in towels...this not only protects them from light but also insulates them from temperature shifts.

To expound on au naturals' post...think of the damage the sun does to your skin, or how lasers are used to remove tatoos (the light breaks up the ink molecules into smaller pieces). So it does the same thing to the delicate molecules of the wine.
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I'd say light becomes a problem when I've had too many the night before and my head hurts;)
What I wen ahead and did was created a box that my fermentation container fits in perfectly, with a door on it.

Im using fluorescent light in here, and had it sitting out at first I hope this doesnt affect it.

I have a closet that I use for my office. I built a wine rack in it to store my bottled wine. I'm in here for an hour or two every other day and then it and out for a few minutes at a time. It has a flourescent light in it. Am I ok as far as light affecting the wine?

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