Attenuation question, and help finish my stout.

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Gofastr1

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I get how to calculate attenuation, but I'm not really sure I understand it. If I have a wort that I want to dry out past intial FG, can I just keep pitching fresh yeast to get multiple fermenations of say 73% (wyeast website mean attenuation = 73% for Irsh ale yeast) attenuation rate? This intuitively doesn't seem right, but I don't know.

My problem: I brewed a stout two weeks ago, with OG of 1.084. Made a nice starter and fermentation started pretty quickly and actively. After three active days fermenting in my 60F basement (temp strips read 67), I moved fermentor into a warm chamber at about 65 and went on vacation. While away, the breaker on my heater cicrcuit tripped and ferm dropped to 58% for a few days. When I got home I read gravity (1.025), fixed the heater problem, warmed the beer up to 68F, roused the yeast and let it go for another 6 days. Had no sign of activity and gravity remained the same at end of those 6 days; I think that I had uneven temps in my mash with some very warm spots. I'd like to get this beer more in the 1.018 - 1.020 range. If I pitch a yeast with higher attenuation (SafeAle US05, for example, for wich Fermentis indicates 81% attenuation) on top of the Irish ale, could I expect to see an 81% attenuation of the current gravity (.025), or an overall attenuation 81% of my OG of .084?
 
Few questions for you; Are you doing all grain or extract? Secondly, if you're going all grain, what temp did you mash at? If using Irish Ale (WLP004), chances are the yeast have done their job and your brew is done fermenting since average attentuation is listed as 71.5%
 
All grain here. Mash was 153 - though as I'd noted, I think I had some hot spots in my mash. Ths was a 37# grain bill in my keggle system, so it takes me a while to mash in and stirring gets difficult, especially as I get to the final 3-4# and try to prevent a "mashover".
I suspect these yeasts are done, however, what I'm wondering is if I pitch another, higher attenuating yeast (Safale US-05?) now at end of primary, or in secondary, will they pick up where the Irish left off?
 
Given your mash temps and yeast, sounds like you're done. Pitching a yeast that can attenuate more probably won't help at all at this point. Your beer at this point has a low ph and a pretty hostile environment given that it's registering an ABV of 7.7%, both of which are detrimental to new yeast.

Did you taste it to see if it's too sweet? Sounds like you've got a pretty good tasting beer on your hands. Chalk this up as experience and tweak your next batch to focus on controlling mash temp and picking a yeast with better attentuation (I'd recommend WLP007 - English Dry)


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Thanks for the feedback, Buckswope.

I've got two 5g pails of this, one of which has some cherry puree in it. Both will get some chocolate, and the non-cherry is going to get some hot chilis. So, while they're a bit sweeter than I'd prefer, they are going to get bottled and savored as dessert/last call beers; IMO, a bit of sweet is ok for such sippers. The last time I made the cherry version, it finished at 1.018, and then finished 3rd, 2nd and 1st in three comps entered; I'm anxiously awaiting the results of the AHA Nationals first round to see how it fares there.

Nonetheless, both pails are going to get a sachet of Safale 05 tonight. If that does kick in, I figure it'll bring it down to the .018-.019 range. If it doesn't, I'll skip two Starbucks next week to make up for the $8 I wasted on yeast. And speaking of next week, I'll be in TO almost all week, working at the mother ship. Will be exploring a few places in the evenings (Surf, Wades and some place south of Agoura that I don't recall the name...) Drop a note here if your interested, or perhaps, just by chance, you can figure out the rest of my "timothyo" eddress at Uncle A?
 
My experiences of other solutions to stuck gravities (beano or champagne yeast, specifically) were less than fantastic. Going the beano route is a lot of work with little room for error. Champagne yeast had little effect in my experiences but I don't see how it would hurt to try a California ale/clean finishing strain. Then hit with gelatin before racking if you have concerns about yeast flavors in the finished product. Or chill if bottling. Cheers.


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I was going to say that re-pitching some yeast will let you know if it is done, but it looks like you already did that.

As a note: I have an Imperial Stout that stopped at 1.020 and I was thinking it was done, but was told by an award winning home brewer that if I thought it was too sweet lager yeast would consume a wider variety of sugars than ale yeasts do and that might help.

Good luck with the AHA
 
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