Fermentation process and the sun

Hi there

I've heard a couple of times that the sun is bad for the beer.
But how much sun is bad, exactly?
I have my beer fermenting in the kitchen in a glass carboy and naturally there's a window, where the sun shines at certain period of the day. Now there's no direct sunlight that hits the carboy, but it's not in the dark, either.
Is that something I should worry about and find a darker place for my young beer, or is that not such a big problem?

Thanks!

put a shirt over it or paper bag. Beer will become skunky leaving it in sunlight.

Find an old shirt and cover the carboy. Sunlight is bad, rather direct or indirect.

I have a black T shirt I have dedicated just for this purpose.

Not a problem if you like the smell of fermented skunk ass
or Heineken...

Any old t-shirt will do but I prefer old Grateful Dead tour shirts, my beer is happier for it

I hope it will be okay after just two days in the light. it still has ~3 weeks of time to ferment untill bottling

Maegnar said:

I hope it will be okay after just two days in the light. it still has ~3 weeks of time to ferment untill bottling

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Skunking can happen as fast as 15 minutes of sunlight exposure:

https://www.homebrewtalk.com/wiki/index.php/Skunking

Oh come on... It's a Belgian Quadruple...
That will be a total waste if it'll go bad...

Is it a better bottle... The boxes them come in have instructions on how to cut out a whole in the bottom that u can flip upside down and completely cover the carboy. Otherwise I may not even trust a regular tshirt (go outside on a sunny day and put it on halfway over ur head and stare at the sun)... i'd go with a towel of some sort. I've seen alot of experienced guys buy and use heavy duty cloth bags

Or just move it to a closet.

What about removing the blanket to check the temperature, is that little bit a problem? I have mine in a box that is in my closet, I cut the box where the tape thermometer is so that I can pull the flap down to see the temp but the closet is so dark that I have to use a flashlight to see it. Would this also cause a problem or what should I be doing differently, besides a temperature controlled environment?

Maegnar said:

Oh come on... It's a Belgian Quadruple...
That will be a total waste if it'll go bad...

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I guess all kinds of outrageous flavors are fine in Belgians. I don't think it will "go bad" though, and I would probably find all kinds of reasons to drink it.

Sunlight is bad for both yeast and hops. Relocate the vessel to someplace that gets zero sunlight, direct or indirect.

Alternatively, you can set up some sort of shield, as others described. If you go that route, keep in mind the potential additional heat that the shield might transmit to your fermentation vessel. For example, a black t-shirt absorbs and transmits more heat from the sun to your body than a white one does.