Can Too Much Blow Off Cause Under-Attenuation?

I recently brewed a stout, 6 gallons into a 7 gallon gallon conical. I aggressively oxygenated (plastic mash paddle connected to a drill) and pitched Denny's Fav (WY 1450).

12 hours post-pitch, my fermentation was unbelievably vigorous. Blow off tube was constantly filled with krausen to the point that the blow off bucket was practically the same color as the beer. However, 2 days later, visual signs of fermentation have ceased and I've now switched to a bubbler (seeing maybe 1 bubble a minute). I checked the gravity and it looks to be about 10 gravity points above my FG. I know the bubbler is not an accurate representation of fermentation, but it looks like the there is no more krausen on the top of the beer and I'm worried it may be under-attenuated.

My questions:

Can too much blow off cause Under-Attenuation?

This was brewed 5 days ago, and I plan on checking the gravity again in 3-4 days to see whats going on. But if it is stuck, should I just agitate the conical a bit to get the yeast back in suspension or throw in a vial of WLP-001? Any suggestions.

I would give the beer two weeks in primary before worrying if it's under attenuated. Yeast will do most of the work the first few days, but sometimes needs more time to get those last few points and to clean up the beer. Saying that, if still concerned, you can raise the fermentation temp up to the mid 70's to help the yeast finish out.

I've never had an issue with under attenuation on crazy fermentations before. If you are under attenuated, I would look elsewhere for the culprit (insufficient yeast to begin with, large temp swings, poor mash conversion, etc)

A couple notes though. I do see vigorous fermentations complete faster than most, 2 days of high krausen is not unreasonable. Also, if you're still seeing bubbles then the gravity is still dropping. Like jdauria said, give it some time before worrying.

Also, no offense intended, but your oxygenation method sounds like a bit of an overkill imo. Oxygenating with air (mixing, shaking, stirring, pouring etc) means that you can only get as much oxygen as is in the air. The maximum possible is 8 ppm from air. If you really feel that oxygenation is the issue I would switch to an oxygen stone and a tank because that's the only way to exceed 8 ppm.

That being said, I've never had an issue and I just pour my chilled wort down a funnel and let the spiral/dribble effect oxygenate for me. Again, that's just my experience. I'm sure other brewers have had vastly different experiences and seen improvement from oxygenation, but power tools definitely sounds like overkill to me.

Looks like the it's crapping out at 1.023. I'm really not looking for a solution now, just trying to figure out why it stopped so high. Anybody have any problems with Denny's FAV 50 (WY 1450)?

I still think I lost active yeast in blow-off, or possibly under-oxygenated. Not quite sure...

I agree with you that excessive blow-off can drive off a lot of healthy yeast. Could be too much of a good thing. I started using a 7.9 gallon fermenter for 5 gallon batches and get no blow-off.

ncbrewer said:

I agree with you that excessive blow-off can drive off a lot of healthy yeast. Could be too much of a good thing. I started using a 7.9 gallon fermenter for 5 gallon batches and get no blow-off.

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Have any recs for fixing the issue? I have a conical, so I don't think rousing the yeast will do much, can't really pick the thing up.

I personally haven't noticed any differences with my oxygenation methods: Single transfer kettle to carboy, paint stirrer on a drill, oxygen stone. Nothing has changed from one to another really.

I don't know if the blowoff caused you to lose enough yeast to stall fermentation I've had it happen a few times with no blowoff losses. I don't know why, but it just stalls out occasionally.

How are you calculating your FG? What attenuation are you at?

Gustatorian said:

Have any recs for fixing the issue? I have a conical, so I don't think rousing the yeast will do much, can't really pick the thing up.

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I'm a little confused, in one post you say your not looking for a solution, then this post...
The only time I have ever tried to rouse the yeast, I blew co2 up the bottom outlet of the conical. Didn't help, I think when the yeast want to sleep, they're done with the job. In my case, the enzymes didn't do their job.

christyle said:

I personally haven't noticed any differences with my oxygenation methods: Single transfer kettle to carboy, paint stirrer on a drill, oxygen stone. Nothing has changed from one to another really.

I don't know if the blowoff caused you to lose enough yeast to stall fermentation I've had it happen a few times with no blowoff losses. I don't know why, but it just stalls out occasionally.

How are you calculating your FG? What attenuation are you at?

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Calculating with refractometer, confirmed with a hydrometer this time. Looks like apparent attenuation is 65% (Denny's AA is usually 75%).

brick_haus said:

I'm a little confused, in one post you say your not looking for a solution, then this post...
The only time I have ever tried to rouse the yeast, I blew co2 up the bottom outlet of the conical. Didn't help, I think when the yeast want to sleep, they're done with the job. In my case, the enzymes didn't do their job.

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I don't think I'll do anything to this beer. Oddly enough, it tastes ok. For future reference though, I'm wondering what people do with conicals. It seems like pitching more yeast would only the a viable option. Does anybody know how to rouse yeast with a conical? Maybe drain some from the dump valve and pour on the top?