Fermenting time

[Greendan]

Where does the 'ferment for two weeks' thinking come from? Given that most kits say 7 days? Once the yeast has done it's thing and you've hit a steady FG why leave it?

[alanywiseman]

During intial fermentation the yeast produce a number of by products.After they have fermented the sugars they turn to these by products resulting in a cleaner beer.

[Greendan]

So they, like, eat their own poo?

[Cozzyb]

No if anything you eat theirs. But basically yeast turns sugar into alcohol, the reason people say 2 weeks or even up to a month, is one, fermentation sometimes is no where near done at 7 days, and two, it gives the yeast more time to finish and clean up the beer etc. I normally try and give it two weeks but 10 days can sometimes be plenty of time if I am in a rush.

But some of the new better kits i.e. not muntons and coopers, state anything from 10-21 days (the new wilkos says 21) so really 7 days would be a little silly to do, as you really aren't giving it chance.

[dcq1974]

Most commercial breweries will primary ferment for 3 to 4 days then cool to condition for say 2 days before casking and storing at cellar temperatures (10 - 14 degrees C) for as long as possible to mature. Fullers certainly follow this process - this is for cask ales.

[jmc]

Most commercial breweries will primary ferment for 3 to 4 days then cool to condition for say 2 days before casking and storing at cellar temperatures (10 - 14 degrees C) for as long as possible to mature. Fullers certainly follow this process - this is for cask ales.

Quite true, but that's in optimum conditions using high pitch rate of brewing yeast that's raring to go.

With an AG with liquid yeast, I ferment until FG static for 3 days in a fermenting fridge, then keg/bottle. Typically 6-10 days pitch -> Keg

For a kit with dried yeast I'd say its likely to take a few days longer to minimise off-flavours so maybe 10-14 days (Its been a couple of years since I've done a kit).

BTW: It would probably be faster if you're pitching onto previous brew's yeast cake

I'm wary of leaving more than 2 weeks, especially in summer as unless sanitation is very good, and its in a air-locked FV with a CO2 cover, it can go off if left for an extended period once its finished fermenting.
I've had 2 of last 50 odd brews go this way, both in summer.