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NB Imperial Stout - High (?) FG?

I brewed the all-grain NB Imperial Stout recipe to the letter last Monday. After a good start, the fermentation quieted down drastically after about 4 days. The Krausen even dropped then which really surprised me.

The OG was at 1.079. After those 4 days, when i saw the krausen drop, i took a quick FG and found it to be at 1.020. Over the past 5 days, i’ve roused the yeast at least once a day. The fermenter was still bubbling, although very slowly. Perhaps one bubble a minute with an airlock. This has been quite consistant. I took another FB reading today and was surprised to see it was STILL at 1.020.

Doing a quick calculation, this is roughly at 74% attenuation. I guess I expected the FG to hit below 1.020. This is the highest FG i’ve seen since i’ve been brewing.

Should I accept this? Would it be worth my time to pitch a new smackpack when i transfer this to secondary? Or is that just silly?

How much yeast did you pitch, and what were the pitching/fermentation temperatures? Warming it up a bit and swirling the fermenter to get some yeast into suspension may get you some additional fermentation, but at 74% ADF it’s probably just finished. 1.020 is a pretty typical FG for an RIS.

I made a standard 1L starter as I usually do for my bigger beers. The fermentation started around 65 deg F (basement temp) and honestly I didn’t see how high it peaked, but after 3-4 days, it slowed dramatically and then the krausen dropped, which was a first for me. I should add that during those 3-4 days, i had considerable blowoff since my sanitized water at the end of the blowoff tube turned dark brown!

As I said, I did take the 2nd FG sample today, and tasted it too - DELICIOUS, even this young. I’ll let it sit in primary for another week or so, then do the usual secondary/keg conditioning.

Even after two years of brewing…i’m still learning!

I think 1020 is pretty decent. I did the extract Imperial stout and ended at 1030. As you said…leave it for another week or so, then secondary/keg condition.

It’s a great beer, and I’m almost out of mine. Need to brew it again, soon!

Pretty good FG, actually. Mine was 1.084 (my own recipe), but finished at 1.028. I had already put it in the bottling bucket with sugar by the time I was actually thinking about the FG (after 4 weeks on the yeast, I oxygenated it for 30 minutes using an aquarium pump). Left it five weeks in the bottle. It’s carbonated nicely - not real heady, probably a pinky’s worth that disappears, but good carbonation for an Impy Stout.

I think yours will be fine. In fact, age these for as long as you can. My first one I made in 2009 started tasting really good about 6 months in the bottle.

Not sure why mine didn’t finish lower. I used a fresh pack of Wyeast 1335, made a 2L starter (for 3 gallons of beer - I was shooting for a 10% beer, and I don’t drink a lot of those. I still had one left that I brewed in 2009), and it took off after 2.5 hours. But I had a quarter pound each of honey malt, crystal 80 and golden naked oats. I also had half a pound each of chocolate malt and roasted malt. 10-12 lbs of 2-row. So I don’t know if all those malts would actually convert.

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