Does fermentation need to be in the dark ?

Hey all, first post from me, got 4 kits waiting for me at home, my first!
Have been reading around and loving home made craft beers for years at fair and markets etc. but been really busy and now finally I have taken my first step into your delightful world!
My question is does the room where my FV sits have to be dark?
The room has a great climate control so the temps can be constant (was thinking 22C) and a tiny basement window (1m x 40cm) on the dark side of my house so never any sunshine, just light.

My first Brews are: Bulldogs - Evil Dog, Raja's reward and Strawberry Pale Ale.
Magrove Jacks NZ Hopped Pilsener

Do you guys have dark FV rooms or cover your FV's with blankets etc?

Just keep all of mine out of direct sunlight...

Brett74 said:

Hey all, first post from me, got 4 kits waiting for me at home, my first!
Have been reading around and loving home made craft beers for years at fair and markets etc. but been really busy and now finally I have taken my first step into your delightful world!
My question is does the room where my FV sits have to be dark?
The room has a great climate control so the temps can be constant (was thinking 22C) and a tiny basement window (1m x 40cm) on the dark side of my house so never any sunshine, just light.

My first Brews are: Bulldogs - Evil Dog, Raja's reward and Strawberry Pale Ale.
Magrove Jacks NZ Hopped Pilsener

Do you guys have dark FV rooms or cover your FV's with blankets etc?

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I put a thick-ish t-shirt over mine.

lightstruck beers can smell skunky.

dad_of_jon said:

I put a thick-ish t-shirt over mine.

lightstruck beers can smell skunky.

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Likewise or i use a thick bin bag.

cheers beercat like the idea.
I've been using an old bath towel, hole ripped for airlock. then a couple of light rain macs.
the good thing about covering the FV is it maintains a steady temp. I find the temp doesn't fluctuate as much if left bare.

Unless you're fermenting and conditioning the beers in clear glass carboys, I can't see that you'd have a problem.
I'm pretty certain that UV light cannot penetrate a white plastic fermentor - I've never ever covered mine & I've had no off flavours. I don't keep them in direct sunlight, mind you - as much to help temperature stability as anything else.

Depending on the yeast you're using, you might find 20C gives a better beer than 22C

Apart from affecting the taste, in a translucent or clear FV the yeast tends to stick to the side nearest any sunlight so, when emptying the FV, as the level drops the yeast falls off the side and can increase the murkiness of the beer being removed.

This is not a drastic problem but easily avoided by covering the FV, which keeps the temperature more stable as well as keeping the FV away from the light.

Thanks guys, recon I might just just cover the window....keep the answers coming...

Just realised that my post could easily be misunderstood re "conditioning in glass". I think of conditioning as a 2-stage process. Firstly, letting the beer stand under airlock for at least a couple of weeks - this lets the yeast absorb stuff you don't want from the beer, and means it clears considerably. This could be done in a glass carboy or demijohn.
The second stage is carbonation, which would be dangerous (and messy!) in anything not designed to withstand pressure.
Guess I should have said "maturing in glass" to avoid misinterpretation!

is there something im missing ? iv done a few kits and a TC or 2 and not heard of this fermenting in the dark ??

to be fair the kits have been done in the white youngs fermenter and the TC's in demijohns. what diffrence does it make fermenting in the dark ?

Ordering homebrew supplies usually results in a large cardboard buildup in my garage. One could probably use those boxes as a cover for any vessel, and it would have some insulation properties too.

I tend to ferment in the downstairs toilet but if I move the fermenter to a warmer/ colder location where the window shines on it I throw a towel over just to be sure.

Covrich said:

I tend to ferment in the downstairs toilet

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Me too. Especially after Draught Bass with a good hot curry...

Personal91 said:

is there something im missing ? iv done a few kits and a TC or 2 and not heard of this fermenting in the dark ??

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The problem is that an unpleasant taste tends to develop in beers exposed to light - especially ultraviolet light - and hoppy beers are more susceptible. The affected beer is known as "skunked" or "light-struck". It is the reason why most bottled beers are in brown bottles.
I've read that it can happen very quickly, although I've not experienced this myself. I've never bothered covering a white plastic fermenter, without any problem, but when I've made trial brews in a clear glass demijohn then I've always covered them up carefully to exclude sunlight.

Hoppyland said:

The problem is that an unpleasant taste tends to develop in beers exposed to light - especially ultraviolet light - and hoppy beers are more susceptible. The affected beer is known as "skunked" or "light-struck". It is the reason why most bottled beers are in brown bottles.
I've read that it can happen very quickly, although I've not experienced this myself. I've never bothered covering a white plastic fermenter, without any problem, but when I've made trial brews in a clear glass demijohn then I've always covered them up carefully to exclude sunlight.

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so the uv rays cause de-natureing of the yeast/enzymes ? it doesnt seem to bother my turbo cider that was in clear bottles

Hoppyland said:

Me too. Especially after Draught Bass with a good hot curry...

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I wouldn't recommend leaving that to Age

The "skunked" problem I think is a gas which is formed and is something to do with the hops, so not a problem with cider, I seem to remember reading how Miller has got around the problem and market beer in clear bottles. But it is a smell released rather than a taste, although to smell anything it has to be dissolved in water.

However not sure if light in the fermentor is good or bad as making the smell while the gas can escape may be better than when trapped in a bottle? I am told you should not drink light coloured beers outside, dark ales will not let the sunlight hit the whole of the beer, but lager should not be drunk outside in the sun light. However I have only read about this I have never smelt it. Although I am sure it does happen, I don't think I would really worry about it.

Yes I have covered the fermentor, and also stuck in inside a fridge and freezer but that was for temperature control not "skunking".

Temperature control is more of a problem. The brew normally ferments OK between 18ºC and 22ºC but this is the brew temperature not the ambient temperature of the room. I found in summer my beers were not as good, and once I moved to brewing in an old fridge I realised my error. Stick on temperature strips show some where between brew temperature and room temperature as they are cooled by the room. Putting a sensor on side of the fermentor and covering the part of the fermentor where the sensor is with something to insulate, I use a sponge, you get very near to temperature in the centre of the brew. So in a room at 22ºC the stick on strip will likely show between 22ºC and 24ºC but centre of brew likely hitting the 26ºC mark.

There is a lot of luck, 9th June this year I started a brew, I needed the refrigeration to reduce the temperature, but by 13th June the temperature was dropping, so had I started a brew on the 14th June, by now the very active part will have passed and it would not matter if the temperature started to rise now on the 20th June, as a lot less heat coming from the brew.

To keep brew at a steady 20ºC the room needs to be at around 17ºC to start with slowly warming to 20ºC after around a week. 40 pints takes a lot of heating so in the Winter a room kept at 20ºC during the day dropping to 16ºC over night is A1 for the brew to start at, as time goes on, 5 to 7 days then put a coat over the brew to keep it a little warmer. In the summer it is just a little too warm.

However not all is lost, the off taste caused by being a little too warm does start to reduce while being conditioned, so 2 weeks brewing and 6 weeks condition instead of 3 weeks brewing and 5 conditioning. As long as you start it during a cool spell warming up latter is not really a problem. The first 5 days is critical after 5 days does not really matter if too warm.

If unsure too cool better than too warm.

Wow, great info here, thanks guys.

My understanding is that the light-induced skunking is due to downstream products initiated by the photodissociation of iso-alpha-acids by ultra-violet light, a mechanism that was discovered in Ghent University in Belgium. It occurs quite quickly with uv light at a wavelength of 250nm (UVA), and is much slower at 300nm (UVB), and disappears completely at longer wavelengths (UVC). Plastic fermentation vessels are typically made from polypropylene or HDPE, and some of the clear plastic carboys are made from PET. The uv transmission of all these materials is high at 400nm, but drops to practically 0% as the wavelength shortens to 350nm, and stays that way at shorter wavelengths. Untreated clear glass, on the other hand, has quite high UVB transmission, and so would present a problem for skunking. So, the conclusion is that skunking from within a carboy is nothing to be concerned about as plastic fvs completely block out the wavelengths of light that cause it. :thumb:

IainM said:

My understanding is that the light-induced skunking is due to downstream products initiated by the photodissociation of iso-alpha-acids by ultra-violet light, a mechanism that was discovered in Ghent University in Belgium. It occurs quite quickly with uv light at a wavelength of 250nm (UVA), and is much slower at 300nm (UVB), and disappears completely at longer wavelengths (UVC). Plastic fermentation vessels are typically made from polypropylene or HDPE, and some of the clear plastic carboys are made from PET. The uv transmission of all these materials is high at 400nm, but drops to practically 0% as the wavelength shortens to 350nm, and stays that way at shorter wavelengths. Untreated clear glass, on the other hand, has quite high UVB transmission, and so would present a problem for skunking. So, the conclusion is that skunking from within a carboy is nothing to be concerned about as plastic fvs completely block out the wavelengths of light that cause it. :thumb:

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I don't know about you guys but that answer convinced me 100%, total thanks Dude!