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Old 07-22-2009, 09:56 PM   #1
marubozo
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Default What is causing high attenuation?

On my first three batches that have gone to bottles I've noticed they are all reaching high attenuation and I'm missing my FG target on the low side by sometimes quite a bit. Each of the recipes are just extract kits with specialty grains and I'm not doing anything different with the recipes other than using a 4.5 gallon boil vs. the 2 or so the recipe instructions use.

A 1 L starter was made with each one about 24 hours in advance of pitching and were pitched into the wort when at or near high kraeusen.

I can post detailed recipes for each if needed, but here are the yeasts and attenuation I've calculated for each:

Cream Ale
wyeast 1056 (expected attenuation: 73-77%)
OG - 1.042
FG - 1.008
Target FG - 1.010-1.012
attenuation = 81%

American Amber Ale
wyeast 1007 (expected att: 73-77%)
OG - 1.058
FG - 1.011
Target FG - 1.014
attenuation = 81%

American Hefe
WLP320 (expected att: 70-75%)
OG - 1.055
FG - 1.008
Target FG - 1.013
attenuation 85.5%

I know that it technically isn't a bad thing and at least my yeast are working, but is it normal to consistently see this? The cream and amber ales aren't too out of the park, but the wheat seems like it really went above and beyond. Is there something in my process that could be doing this? Is it really something to not even worry about? I just don't want all my beers to be finishing drier than they should.

And yes, hydrometer readings were taken at either 60 degrees or corrected, and the hydrometer seems calibrated according to a plain water reading. The formula I was using to calculate apparent attenuation was: [(OG-FG)/(OG-1)] x 100

Anyway, I'm relaxed and I'm drinking a homebrew right now, but I'm just curious and trying to learn more about the whole process. Thanks



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Old 07-22-2009, 10:40 PM   #2
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What temperature are you fermenting at?

Edit: Also, the gravity on all those is fine, but Ilike my beer a little dry.



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Old 07-22-2009, 10:45 PM   #3
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Pitching at low-mid 60s and fermentation never cracks 70-71 during its most active period for these three brews.

All three have spent close to the same amount of time before bottling. Cream ale went 10 days in primary, 2 weeks in a secondary bottle and then bottled. Amber ale was exactly the same, and the hefe went 21 days in just primary before bottled.

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Old 07-22-2009, 10:52 PM   #4
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Did you buy these kits from the same source and about the same time? It's possible that the higher attenuation is just due to the extracts being more fermentable that average, because extracts do vary quite a bit.

You might consider getting a precision hydrometer for FG readings. I use one and I do see differences between that and my regular hydrometer, even though they both zero out the same.

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Old 07-22-2009, 11:13 PM   #5
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i agree with David. also some yeast ferment more than others. check the yeast packages. it should say on there what kind of attenuation you can expect.

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Old 07-22-2009, 11:16 PM   #6
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I always go by actual attenuation, which gets me this for your batches:

1:65.90%
2:65.96%
3:69.7%

The formula for real attenuation is

real extract = 0.1808 * original extract + 0.8192 * apparent extract

Basically just going by apparent attenuation will get you a higher number because it's not factoring the extra ethanol.

explaination:
Understanding Attenuation - Home Brewing Wiki

A quick calculator for ABV, apparent and real attenuation: pint.com.au - Brewing Calculator - Alcohol and Attenuation

and a more scientific one!
http://www.realbeer.com/spencer/attenuation.html#attenuation

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Old 07-22-2009, 11:18 PM   #7
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Quote:
Originally Posted by TipsyDragon View Post
i agree with David. also some yeast ferment more than others. check the yeast packages. it should say on there what kind of attenuation you can expect.
Right, that's why I listed the expected attenuation as per each yeast I used. Especially the hefe yeast, they call for 70-75% and it really did almost 86%. That seems like a fairly substantial difference.

To answer the other question, two kits were from midwest and purchased within about a 2 week period, and the other was from AHS.

I know the numbers aren't out of the park crazy, but it usually seems like most people have issues with not getting the yeast to attenuate enough, and I don't want all styles of my beer to finish dry if it's something I can fix or if it's something I'm doing wrong.
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Old 07-22-2009, 11:24 PM   #8
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Quote:
Originally Posted by davesrose View Post
I always go by actual attenuation, which gets me this for your batches:

1:65.90%
2:65.96%
3:69.7%

The formula for real attenuation is

real extract = 0.1808 * original extract + 0.8192 * apparent extract

Basically just going by apparent attenuation will get you a higher number because it's not factoring the extra ethanol.

explaination:
Understanding Attenuation - Home Brewing Wiki

A quick calculator for ABV, apparent and real attenuation: pint.com.au - Brewing Calculator - Alcohol and Attenuation

and a more scientific one!
Attenuation and related formulae
Thanks for giving me a headache. I think I need about 6 more beers before I can make any sense of that
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Old 07-22-2009, 11:28 PM   #9
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Quote:
Originally Posted by marubozo View Post
Thanks for giving me a headache. I think I need about 6 more beers before I can make any sense of that
I was just re-affirming that you're not a miracle brewer who somehow gets better then expected attenuations Don't worry, seems like you're doing really well with your first 3 batches, as your attenuation is getting better (and is still not higher then absolute attenuation for all these yeasts). RDWAH (ONE) Homebrew


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