Why is my attenuation so poor / variable?

[curtw]

I keep a spreadsheet of all my brews, and I just added a column for yeast attenuation, based on the http://www.whitelabs.com/beer/homebrew/beginners-attenuation-and-flocculation-definitions. Looking at it, I see some (seemingly) surprisingly low attenuation values:

WLP 001: 72% (OG: 70; FG: 19)
WLP 005: 66% (OG: 66; FG: 22)
WLP 300: 61% (OG: 55; FG: 21)

All of these were 3 gallons into fermentor; all were done with a starter and stir plate, all had viable cell counts as per brewersfriend's yeast calculator.

All were fermented for ~2 weeks in a 5 gallon bucket, air temperature roughly 62-64F (unheated room in my house). Pitch temperature was probably 70F for each of them. Mash temp for each of these was about 150-151F, BIAB, and very little crystal grains (e.g., the WLP 001 was 8# 2-row, 1# Munich, and 0.5# crystal 40).

Am I doing anything wrong? Should I not be expecting more attenuation? I don't have proper fermentation temp control, but this time of year, the room temperature is pretty stable and pretty low.

Thanks!

 

[balazs]

From the info you gave about your process you should be getting a lower finishing gravity. Couple questions. Do you think the temperature in the room your fermenting is dropping at night? Are you using oxygen or aeration? If the temp is dropping at all in that room that can make for an under attenuated beer. Also, lack of dissolved oxygen in the wort can do the same.

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[g-star]

Are you using a hydrometer or refractometer for FG readings?

 

[LLBeanJ]

What are you using for a thermometer? You could be mashing higher than you think you are. I had the same problem until I replaced my $20 CDN digital with a Thermapen.

 

[balazs]

What are you using for a thermometer? You could be mashing higher than you think you are. I had the same problem until I replaced my $20 CDN digital with a Thermapen.

I did the exact same thing. I was using the $20 CDN and got tired of questioning the readings I got from it. Wife got me the Thermapen for christmas. Well worth the $90.00. The majority of home brewers do not want to spend that much on a thermometer but think about it. Temperature is everything in brewing. By it once and you never have to worry about inaccurate readings anymore...as long as you take care of it.

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[hawktrio]

I have had the same poor attenuation issues consistently and I have a CDN and an STC-1000 that I now do not trust. I cannot even calibrate the CDN and have contacted the manufacturer who rightfully offered to repair/replace it under warranty. I suspected my mash was actually too high so reduced it by 4℉ according to my untrustworthy CDN for a couple of batches. I also suspected my fermentation temps from an STC-1000 may be reading higher so I raised my ferm temps too by 4℉. On my first batch using these changes I finally hit all my numbers - 1.039 down to 1.011 in 7 days on JZ's Special Bitter. Sample was a little high in fusels so I think I'll only adjust ferm temps up by 2℉ (instead of 4&#8451 in future but as previous poster said - temp is everything.

 

[EarlyAmateurZymurgist]

A Thermapen is a nice piece of kit, but it is more of a "want" than a "need" when it comes to brewing. One can purchase a nice 12" environmentally-safe glass lab thermometer that is more than accurate enough for brewing for around $20.00 (e.g., an H-B Instrument No. 30505T Celsius/No. 30535T Fahrenheit).

 

[mblanks2]

I agree with everything above that has been said about temperature but also consider your oxygenation. How well is that occurring. Do you even consider it? Shaking vigorously with a plugged carboy is all that I do for 1 to 2 minutes and have never had an issue with attenuation.
I have a set-up for pure oxygen delivery and have never used it. I just completed an IIPA with an OG of 1.094 and my FG was 1.005. edited to add that fermentation temperature was at 61*F
If you find that your mashing temps are good then make sure you are pitching the proper amounts for your gravity and oxygenate properly and you should be good.

 

[DoWBrewer]

I had a beer stuck at 1.020 last week. I started swirling the fermentor twice a day and wrapped it in an electric blanket to bring it up to 68. It finished a week later at 1.009. I think ramping the temp should help. On the thermometer discussion, I realized my mash thermometer was off by 8 degrees. Luckily, for most of my beers that worked out just right for a step mash. I mashed at 140-145 and sparged in the 150s. I really want a thermopen.

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[curtw]

Thanks all for the replies.

I hadn't considered my thermometer being off -- it's a fairly cheap digital instant read, for home kitchen use. I wonder if I've just been mashing too darn hot all these brews?

For aeration: I don't have oxygen, I just vigorously swirl in my fermenting bucket for 3-5 minutes after pitching. For better or worse, I've got a standard 6-gallon bucket, and only putting 3.25 gallons into it -- so I've got lots of room to swirl .

The temperature in the room I'm fermenting in is pretty stable -- it might drop a degree at night, and warm a degree in the day, but no 5 degree swing, for example.

And I'm using a hydrometer for all gravity readings -- and it seems to be pretty true as far as I can tell.

I'm going to suspect the thermometer first, and at least see if I can't calibrate it against a better one somewhere.

Thanks!

 

[hawktrio]

Ok brew #2 for me tweaking temps - slightly lower mash and slightly higher ferm temps to fix low attenuation. Result a success with an IPA going from 1.066 to 1.010 in 5 days. From kettle to glass in 10 days including dry hop. This is a major improvement for me as my problem has been persistent since I started brewing a year ago. Guys and gals do calibrate those thermometers or at least try to figure out their offset amd work around that.

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[jrfehon]

Do you use yeast nutrients? I brewed an IPA with WLP001 last month and an IPA with US-05. In two weeks I got 85% attenuation from each. There are other variables which people here pointed out but try yeast nutrients in your next brew. A 1.5oz container of nutrients costs around $3 and will last you a long time (you only use 1/2 teaspoon per 5 gallon batch). At that price its a no brainer in my book.

 

[hawktrio]

+1 to yeast nutrients. Another beginner mistake I've made is with the temp of the beer when taking the FG reading. Post cold crashing and for consistency the beer needs 30-60 mins at room temps to warm to a similar temp to that of your initial OG reading. A recent IPA I brewed had a cold FG of 1.014 but after warming it went to 1.010. I new it was low as it finished nice and dry.

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