Low attenuation problems

[gyoder]

I'm hoping someone can point me in the right direction. Every all-grain brew I've done I can't seem to get my finishing gravity past 1.018. It doesn't matter what the starting gravity is. I keep my mash temps low, around 149 or 150, I pitch more than enough yeast and I add yeast nutrient. The latest brew, a 1.050 brown ale, has petered out at 1.020. I can't even describe my level of frustration. My fermentation temp is the only thing I can think of. The room is a constant 68 degrees, but the temp strip on the carboy always goes up to around 74 degrees at the peak of fermentation since it's an exothermic process. If anyone has any advice I would greatly appreciate it. I'm at my wits end.

Prost,

Greg

 

[joshpooh]

Check the calibration on the thermometor that you use to measure mash temperature. You may be mashing high and not know it. Another thing to consider is the yeast strain you are using. The fermentation temperature is not your problem a higher temperature should cause more attenuation not less.

 

[Seawolf]

Check the calibration on the thermometor that you use to measure mash temperature. You may be mashing high and not know it. Another thing to consider is the yeast strain you are using. The fermentation temperature is not your problem a higher temperature should cause more attenuation not less.

And you're not killing your yeast. That happens at 110F and you're nowhere near that. I would check that thermometer. I use two every time I brew because my first thermometer wasn't accurate. You always have to have a back-up.

 

[s3n8]

I too am having similar issues, however, I am a complete newb, and I am sure you have thought of this, but how are you aerating your wort? I recently tried an aquarium pump and stone to try getting more o2 dissolved to get the yeast more excited about doing their job. First fish-bubble brew is 4 days old, so I can't tell you how it turned out yet.

 

[ajf]

As well as checking the thermometer, check the hydrometer. Mine reads 3 points high.
As has already been said, a low attenuating yeast could help to contribute to the problem as could inadequate oxygenation.
Excess crystal malts (or other malts that leave a large amount of unfermentables) could also be responsible.

I doubt that any one of these could be the cause, but it could be a combination of several of them.

-a.

 

[WBC]

What yeast are you using and is a starter used? Some yeast do not attenuate well. If a starter is used the yeast have time to soak up water and get going. There should be no more than 10 degrees difference between wort temp and the yeast that is being pitched. Nottingham and Fermentis safale are good dry yeasts and should be OK if dry pitched depending on their expiration date. I personally like to use liquid yeasts and propagate to make more as I make 12 gallons of lager at a time. For ales I use both dry and liquid at times because some strains of yeast are not available at short notice. I always aerate with oxygen if I can but sometimes I just shake the carboy a few times during the first 6 hours after pitching.