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-   -   Imperial Stout - concerned about attenuation (http://www.homebrewtalk.com/f163/imperial-stout-concerned-about-attenuation-368153/)

nemis79 11-16-2012 02:44 PM

Imperial Stout - concerned about attenuation

I brewed a 5 gallon batch of Imperial Stout on Sunday with OG 1.094. The mash temp was 150F. I made a starter using mrmalty's calculator, 2 tubes of WLP007 and 1,5L wort.

I pitched the yeast at 62F and let it rise naturally to 65F where I've kept it for the last 5 days in my temp controlled refridgerator. I pulled a 2dl sample which I've kept in a jar with a lid on in the same fridge, also for 5 days.

The airlock activity has almost stopped, so I checked the gravity today with the following results:

5 gallon fermentation bucket: 1.034 64% attenuation
2dl jar: 1.022 77% attenuation

Considering this discrepancy and the airlock activity, should I be concerned that the gravity is close to final? Or should I be patient and wait 1-2 weeks to hopefully reach an attenuation in the low 70s? Or pitch more fresh yeast?

Thanks for any input.

jtejedor 11-16-2012 03:32 PM

If the the smaller sample got down to 1.022 I would think the larger batch should also get to about that too. I would rouse it by gently stirring up the yeast if they have mostly settled and if possible let the temperature rise a bit to 70+. That should give you that last little boost to get a few more points out of it. If you don't get anymore activity after a few weeks you could pitch fresh yeast but it might have to be a very large pitch for it to do anything.

nemis79 11-16-2012 05:31 PM

Thanks. I will take another gravity reading in 1-2 days. If it hasnt moved i will try to rouse the yeast (cant see if it has been settled without popping the lid on the bucket)

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