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Old 10-05-2009, 06:17 PM   #1
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Default Og -> Fg

My first batch of NB Cream Ale is done primary fermentation (consistent SG readings of 1.011), and I'll be bottling at the end of the week. The samples I'm taking for hydrometer readings look, taste, and smell like beer, so I'm not all that worried about the final product, but...

Among other mistakes, I forgot to take an OG reading, so I have no idea where I want the FG reading to end up. Again, I'm not too worried about this batch, but if I screw this up in the future, is there any way to tell where final gravity *should* be for a given OG?

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Old 10-05-2009, 06:18 PM   #2
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Well if it's an extract recipe it doesn't really matter what YOUR OG reading was. As long as you topped off to the correct final volume for your recipe (5, 5.5. or 6 gallons depending on the kit or recipe) then what the recipe says your OG should be is correct.

Extract recipes are fool proof that way, regardless of whether or not you mixed it up good enough initially. If your recipe says your OG for 5 gallons is, let's say 1.056 you can bet it is close enough to 1.056 for government work....and if your recipe doesn't say what the OG should have been, you can imput it into any brewing software, including the free online http://beercalculus.hopville.com/recipe

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Old 10-05-2009, 06:24 PM   #3
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Yeah, that much I understand. But from what I've read, FG can be affected by things like infection/water minerals/other stuff, so if I only have the recipe's OG, is there a way to figure out where the FG should be assuming everything goes right? I figure that if I have an FG reading way off from where it should be, it can at least help figure out what went wrong.

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Old 10-05-2009, 06:32 PM   #4
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I took at look at Northern Brewer's website, and the expected FG was not listed (in my experience, it is usually listed on the kit specification page). Considering that, I went to the BJCP Style Guidelines (if you don't know, that is the Beer Judge Certification Program, which is pretty much the golden standard for beer style specifications) and they list the final gravity for a Cream Ale is 1.006 - 1.012, so based on that, I'd say you're just fine.

BJCP 2008 Style Guidelines - 6A Cream Ale.

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Old 10-05-2009, 06:35 PM   #5
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you can do this by looking at the attenutaion of the yeast that you use. Most are around 75% so take your OG say 1.050 so 75% of that is .0375 Subtract that from your OG and you come up with 1.0125 Mind you this is just an estimation. Yeasts have a mind of their own and will finish when they are good and ready some are lazy and need a little help. Others will get the job done in a day.

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Old 10-05-2009, 06:42 PM   #6
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DRoy, that website's exactly the kind of thing I was looking for. Thanks.

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Old 10-06-2009, 02:55 AM   #7
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Quote:
Originally Posted by Benjibbad View Post
you can do this by looking at the attenutaion of the yeast that you use. Most are around 75% so take your OG say 1.050 so 75% of that is .0375 Subtract that from your OG and you come up with 1.0125 Mind you this is just an estimation. Yeasts have a mind of their own and will finish when they are good and ready some are lazy and need a little help. Others will get the job done in a day.
I have my batch sheets set up in ExCel and the above formula is what I use to get a guestamation of where I should expect the FG to be. Compare that result to the BJCP Guidelines that DRoy mentioned and you can get an idea whether you are close to the style you're trying to brew.
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