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Old 02-06-2013, 01:28 AM   #1
anbowden
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Default Over-attenuation(extract)

Hi guys, I've brewed about 6 batches of extract so far, and I've incorporated more and more techniques that I read on here with each batch. With my recent batches I've started fermentation on the cool end of the yeast spec and then after active fermentation starts to slow, I'll bump the temperature up a few degrees slowly("diacetyl rest" maybe). After that, I'll let it get cold again("cold-crashing" perhaps).
I feel this has really helped my beers get down to a lower FG, but it appears as if they're over-attenuating. My latest example:
Innkeeper extract 5 gal. batch from Northern Brewer
Wyeast 1469 with a ~700mL yeast starter
Attenuation spec: 67-71%
OG: 1.043 (after temp. correction)
FG: 1.004 (after temp. correction)
Apparent Attenuation: 90%

I haven't calibrated my hydrometer with distilled water recently, but I did use tap water @ 60 and my hydrometer read 0.998, so I don't think it could be too far off.

On one hand, I'm happy to get the extra ABV, but on the other I'm afraid it will make the beers taste too "watery" and not full-bodied. What do you guys think?

Thanks,
Andy


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Old 02-06-2013, 01:40 AM   #2
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I didn't know you had to calibrate hydrometer! Let me know more? Or you talking about refractometer?


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Old 02-06-2013, 01:47 AM   #3
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I doubt you're overattenuating from a massive overpitch. For a 5 gallon batch of 1.043 using 1 pack of 1-month-old liquid yeast, you'd need approximately 1.5L of simple starter or 750ml of a stir plate starter just to hit the sweet spot.

Like benco, like phrase "calibrated hydrometer" throws red flags. I'm thinking this is a measurement or calculation error.

Do you mean refractometer? If so, did you apply correction for alcohol content? Are you measuring in Brix and making a calculator conversion?
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Old 02-06-2013, 01:51 AM   #4
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Hydrometers can't be calibrated because you can't adjust them, but they can and should be checked with 60 degree water. Refractometers need to be calibrated and IMO should always be checked against a hydrometer, but they always read high for a FG reading until you run the adjustment formulas, not low.
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Old 02-06-2013, 01:52 AM   #5
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Good point, "calibrated hydrometer" was a poor choice of words. I'm trying to say that my hydrometer is not likely significantly inaccurate.

Andy
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Old 02-06-2013, 01:58 AM   #6
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Quote:
Originally Posted by bottlebomber View Post
Hydrometers can't be calibrated because you can't adjust them, but they can and should be checked with 60 degree water. Refractometers need to be calibrated and IMO should always be checked against a hydrometer, but they always read high for a FG reading until you run the adjustment formulas, not low.
I've had "attenuation problems" with my dual-scale ATC refractometer when I read the OG in SG and then the measurement for FG in Brix. Cheap refractometers like those found on eBay use a SG scale that doesn't compensate for the non-simple-sugars in wort, so you can use either scale, but you must stick to that one. In that case, it looked as if I had a 91% attenuation, when in reality I had a spot-on 74% attenuation using Chico strain.

Doesn't look like that's the case here since the OP confirmed he's using a hydrometer.

OP, are you sure you read the hygrometer correctly? 1.014 would be easy enough to read as 1.004, and it would be a 67% attenuation.
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Old 02-06-2013, 02:20 AM   #7
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Quote:
Originally Posted by thadius856 View Post
OP, are you sure you read the hygrometer correctly? 1.014 would be easy enough to read as 1.004, and it would be a 67% attenuation.
I can't be 100% sure, and my sample is my stomach now, but I see your point(I could've quickly interpreted the "10" as 1.000 instead of 1.010). At this point(bottled) is there any way to check, i.e. will the added sugar significantly throw off my SG reading?
I'm contemplating whether it's worth it for me to waste a 12 oz. beer to check the SG.
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Old 02-06-2013, 02:33 AM   #8
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I wouldn't say it's worth the bottle. It's your call though.

I'd just wait until conditioned, take enough for a sample, and drink the rest. Be sure to let it warm and shake out some CO2 before measuring again.

Good luck.
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Old 02-06-2013, 02:41 AM   #9
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Minor point here, but you can and should calibrate your hydrometers. Calibrate may not be the technically correct term, but the principle is the same...ensuring you know how to read your hydrometer. To "calibrate" one, simply float it in distilled water at 60 degrees. If it's properly calibrated, it will float at 1.00. If not, it will be either higher or lower than one and you must always include that variation when taking a reading. Otherwise, your readings will be consistently wrong.
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Old 02-06-2013, 02:38 PM   #10
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I think "correcting" or "determining correction value" would probably be a pretty suitable term.


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