Why 3 Weeks in Fermenter?

So I know the general wisdom is to just leave beer in primary for 3 weeks without thinking about it. And I pretty much follow that advice. My beers are all around 1.050 OG, and I have fallen into a rhythm that works -- 18 days in fermenter, 3 day cold crash, transfer to keg. My beer has always been at FG by the time I get to the 18 days and by the time the cold crash is done the trub and yeast are in a nice compact layer on the bottom.

I have no problem with this, but I got to thinking about it after reading Sam C.'s book about Dogfish Head and after visiting another small craft brewery. If I remember right, Dogfish Head leaves their pale ale in fermenters for less than 2 weeks. And the local craft brewery transfers the beer at the 2 week mark. Is there something different about their process that allows them to move things more quickly, or is it just that 3 weeks is a good rule of thumb that makes things sort of foolproof? I have no intention of changing my process at this point, I was just curious.

It's just a rule of thumb that errs on the side of caution. I've had beers bottled after a week and others require more than a month.

You also have to remember

1) They are mass producing a beer, going from 2->3 weeks just decreased your output by 50%. If its done fermenting after 2, there's no reason to leave it in there if you are bottle conditioning your beer like they do.

2) They have huge conical fermenters, where things like autolysis of the yeast can start to happen at a much more rapid pace than we will ever see home brewing in 5 gallon carboys/buckets. Imagine hundreds of gallons of beer and the downward force it must impart on a TINY(relative) conical port at the bottom where all the yeast flocculates too. That yeast is getting pummeled!

For normal gravity beers, it's just been my safe zone. You certainly can do it sooner if fermentation is done or let it sit longer if you choose.

FuzzeWuzze said:

You also have to remember

1) They are mass producing a beer, going from 2->3 weeks just decreased your output by 50%. If its done fermenting after 2, there's no reason to leave it in there if you are bottle conditioning your beer like they do.

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I certainly understand this is why they do it. I was just wondering if there is a reason that their beers would finish fermenting/conditioning more quickly.

unionrdr said:

There process uses whirl pooling brite tanks & things like that to clear the beer without having to wait for it to settle out as we do on our smaller scale. Plus as was mentioned,autolysis happens at a much more accelerated rate on such a large scale & gravimetric forces.
In my experiences,3 weeks is an average time frame to get the beer to finish fermenting & clean up/settle out clear or slightly misty before packaging. This is with average gravity ales,though. Darker &/or heavier beers take longer in my experiences thus far.

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The craft brewery that I visited is not waiting for the haze/cloudiness to clear from their beer. Their pale ale is considerably cloudier than mine by the time I am drinking it. I'm guessing that my longer process is part of the reason. I guess I am just wondering why we preach to people 3 weeks in fermenter, 3 weeks in bottles at 70, and one week in the fridge. It seems like the bigger issue is the total amount of time from brewing to drinking (assuming it hits final gravity before bottling) rather than the specific breakdown of that time.

Like I said, I don't plan to change anytime soon, this was really just a question to spur discussion. I like to know the "why" and understand root causes.

rklinck said:

I certainly understand this is why they do it. I was just wondering if there is a reason that their beers would finish fermenting/conditioning more quickly.

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It's a few things...

They have better control over their yeast than many homebrewers, they're often filtering/centrifuging their beer and thus get clear beer faster, the large fermenters allow warmer and thus faster ferments than we can do, and (perhaps most importantly) they've run the same batches hundreds or thousands of times so they know exactly what to look for.

The experience is a big part. If you know what to look for, it's easy to pull a hydro sample and know if a beer is ready. I don't usually need to wait more than 2 weeks, but I know how to tell if I do need to. For newer brewers who might not know what green beer tastes like, it's just safer and easier to recommend waiting.