Author Topic: FG Question  (Read 462 times)

Online flbrewer

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FG Question
« on: July 11, 2014, 10:19:55 AM »
How many days should I check for FG before knowing fermentation is done?
Is there a way to know estimated FG based on OG?

Offline morticaixavier

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Re: FG Question
« Reply #1 on: July 11, 2014, 10:28:17 AM »
How many days should I check for FG before knowing fermentation is done?
Is there a way to know estimated FG based on OG?

check first when things settle down, krausen drops. check again in ~ 3days. if it has not changed at all it's done. you can leave it alone for a while longer if you wish/must. but mostly let taste be your guide. how does it taste on that second sample day? if it's clean and tasty and the gravity hasn't changed you are good to go at any time.

you can also perform a forced (or fast) fermentation test. Take a sample, say 10 floz, of your wort into a quart mason jar and pitch a LOT of yeast into it. preferably the same strain you are fermenting with. Keep that sample somewhere warm (not a problem in FL this time of year i suspect) and give it a swirl every once in a while. after just a couple days that sample should be obviously done with yeast dropping out and everything. take a gravity reading on that. that is your theoretical maximum attenuation for that wort.

you can't really estimate well based on OG because every wort has a slightly different sugar profile and will ferment to a slightly different FG. with extract brews it's easier to estimate if you stick with the same maltsters products because they are pretty careful to produce consistent product.
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Offline mattybrass

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Re: FG Question
« Reply #2 on: July 17, 2014, 11:38:28 AM »
There are so many variables that contribute to how long a beer ferments for its hard to predict a time without knowing them. Temperature, OG, Starter or no starter, oxygenation vs splashing/stirring/shaking etc.

I typically do a 10-14 day primary fermentation which gives the yeast plenty of time to clean up after themselves once they've finished fermenting the wort.

Online S. cerevisiae

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Re: FG Question
« Reply #3 on: July 17, 2014, 11:55:33 AM »
I typically do a 10-14 day primary fermentation which gives the yeast plenty of time to clean up after themselves once they've finished fermenting the wort.

+1

I use the same primary period, mainly due to my schedule.  I perform all of my brewing-related chores between Friday evening and Sunday night.  Fermentation is rarely completely finished in a week, so I usually rack after two weeks
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Offline mattybrass

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Re: FG Question
« Reply #4 on: July 17, 2014, 12:05:14 PM »
I typically do a 10-14 day primary fermentation which gives the yeast plenty of time to clean up after themselves once they've finished fermenting the wort.

+1

I use the same primary period, mainly due to my schedule.  I perform all of my brewing-related chores between Friday evening and Sunday night.  Fermentation is rarely completely finished in a week, so I usually rack after two weeks

+1 to doing that time because of my schedule. I usually do my racking/kegging etc on Saturday when i get home from work.

I also agree that fermentation is rarely complete in a week. Just because FG has been reached doesnt mean the fermentation is complete. The beer needs to sit on the yeast cake for a few days post FG being reached for the yeast to clean up all the "mess," off flavors & aromas, they made while fermenting.

Online HoosierBrew

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Re: FG Question
« Reply #5 on: July 17, 2014, 12:10:53 PM »
+2.  I never keg in less than 2 weeks, partly because of my schedule and partly because I want the beer to clear a good bit and the yeast to clean up thoroughly after itself. Actually, it's 2 - 3 weeks then into the keg most times.
Jon H.

Offline brewinhard

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Re: FG Question
« Reply #6 on: July 18, 2014, 01:29:14 PM »
I do not even check for a final gravity until a minimum of 2 wks has passed and the krausen has dropped (most of the time).  By that point, the beer has had enough time on the yeast cake to clean up (providing it is an average gravity ale), and this not only minimizes work for me, but also reduces chances of oxidation or infection. 

Offline klickitat jim

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Re: FG Question
« Reply #7 on: July 18, 2014, 05:19:26 PM »
The two beers I'm doing today are getting an OG reading. My next reading will be in three weeks and I will take an FG reading in a year.

Offline alestateyall

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FG Question
« Reply #8 on: July 18, 2014, 07:58:56 PM »
I generally measure FG twice. Once when the krausen falls and once when I am ready to keg the beer.

99% percent of time you know fermentation is done from visual clues.

I check FG just in case fermentation stalled, so I have an excuse to taste a sample, and to know the ABV.

PS. My beers usually stay in the primary 3-4 weeks. Staying in the fermenter that long I think I could get by without a hydrometer.
Tommy M.
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Offline brewinhard

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Re: FG Question
« Reply #9 on: July 20, 2014, 07:46:58 AM »
PS. My beers usually stay in the primary 3-4 weeks. Staying in the fermenter that long I think I could get by without a hydrometer.

Agreed...

Offline brouwer

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FG Question
« Reply #10 on: July 20, 2014, 09:52:38 PM »
I'll do a minimum 2 weeks in primary. 1 week in I'll check SG. Nearing the end of the second week I'll keep checking SG daily until I reach 2-3 days with the same reading.


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« Last Edit: July 20, 2014, 10:05:59 PM by brouwer »