Author Topic: Terminal gravity  (Read 558 times)

Offline JohnnyC

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Terminal gravity
« on: January 27, 2016, 11:22:33 PM »
Say I have a beer I mashed at 152. It had an OG of 1061. I pull a sample and find an SG of 1016. or an apparent attenuation of ~73%. The yeast I used has an apparent attenuation range of 69-73%. Do I need to pull a sample 3 days later or is it done. It tasted and smelled yummy, by the way.

Offline HoosierBrew

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Re: Terminal gravity
« Reply #1 on: January 27, 2016, 11:28:29 PM »
Please don't ever use those attenuation rates to decide if you're at FG - those are estimates based on a standardized wort to compare various strains to each other. The ONLY way to know your yeast is done is to take 2-3 hydrometer readings each a day or two apart. If those readings are all the same, then you'll know you're at FG. You run the risk of bottle bombs if you don't verify FG this way.
Jon H.

Offline tommymorris

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Re: Terminal gravity
« Reply #2 on: January 27, 2016, 11:29:16 PM »
There are lots of factors. Your experience with the yeast, with that recipe, are you kegging or bottling, your experience recognizing the end of fermentation...

In the end, it is just easier (and safer) to recommend waiting 3 days and checking gravity again.

Offline Frankenbrew

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Re: Terminal gravity
« Reply #3 on: January 27, 2016, 11:30:20 PM »
Patience is a virtue. What's three days when great beer is involved. The chances are good that it is done, but you won't know for sure until you can measure it.
Frank C.

And thereof comes the proverb: 'Blessing of your
heart, you brew good ale.'

Offline brewinhard

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Re: Terminal gravity
« Reply #4 on: January 28, 2016, 12:12:15 AM »
For what its worth, I usually only take one gravity reading (at packaging time) but this is after allowing the beer to properly ferment and condition for at least 2 weeks.  I also have brewed at least a couple hundred beers and know my yeast and fermentation signs well.

Offline HoosierBrew

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Re: Terminal gravity
« Reply #5 on: January 28, 2016, 12:17:26 AM »
For what its worth, I usually only take one gravity reading (at packaging time) but this is after allowing the beer to properly ferment and condition for at least 2 weeks.  I also have brewed at least a couple hundred beers and know my yeast and fermentation signs well.

Same here. Mine are generally in primary 2-3 weeks. Like you say, I pitch plenty of healthy yeast and have brewed many, many beers. I was just a little skeered of somebody assuming the beer was done based on a stated attenuation range from a different grist. I brewed for several years taking multiple FG readings though.


Edit -  On big beers I do multiple FG checks though, since it can take so long to get there.
« Last Edit: January 28, 2016, 12:41:38 AM by HoosierBrew »
Jon H.

Offline majorvices

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Re: Terminal gravity
« Reply #6 on: January 28, 2016, 03:26:10 AM »
The only time I take 2 FG readings is when I am surprised at how low the first is! But as you guys have said, this is after years of brewing. For new folks it is best to make sure.

Offline Bob357

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Re: Terminal gravity
« Reply #7 on: January 28, 2016, 03:51:30 AM »
I agree with most who responded. Never rush to packaging. Err on the side of quality, not time or thirst. Personally, regardless of the beer, I never package less than 3 weeks from brew day. Almost all of my beers are primary only and the only post fermentation gravity reading I need is at the time of packaging.

 The yeast's job isn't done when the air lock/blow off ceases to bubble. When active fermentation ends, the yeasts need time to clean up the by-products they have created during fermentation. This applies to ales as well as lagers. Lagers generally require a diacetyl rest, which dictates raising the temperature  several degrees for a few days, and generally an aging at near freezing temperatures for several weeks to achieve the proper profile.

Ales, with the exception of some high gravity types, benefit from an extra week or so before packaging. If fermented at the lower end of the yeast's temperature range, raising the temperature a few degrees helps according to some sources. Higher gravity ales benefit from bulk aging, sometimes for several months,

Once you have read and brewed for quite some time, you may discover ways to expedite the process. I have been brewing for quite some time and still prefer patience. There are many very good beers out there to sample while You wait for yours to reach its peak.


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