Attenuation

I brewed a Northern English Brown and it fermented well for about 12 days. After 12 days at 68 with no activity, I raised the temp to 70 for an additional 4 days for a diacytl rest.

After those 15 days, I did my SG reading and found that it had stuck at 1.020. I then pitched a Danstar Nottingham (only thing on hand) to try and kick start it, but after 8 more days there was still no activity.

I needed the fermenter space so I kegged it hoping that it would be at least be drinkable. That was a month ago. I tried it yesterday and nope....it is way to sweet. I've heard that some probrewers pitch a lager yeast when attenuation isn't reached.

Would that be feasible to do considering how long this brew was in the keg under carbonation? I know I risk contamination with anything I attempt to do but I'm stymied. I really don't want to feed the snails. Any ideas?

What was your OG? What yeast did you initially use?

Why would a lager yeast do what an ale yeast can't?

1.050 WLP 002

I have heard a notable brewer say that when they don't hit their expected attenuation, the will pitch a Lager yeast to bring it down.

Could it be the 1.020 Curse?

Catch-22 said:

1.050 WLP 002

I have heard a notable brewer say that when they don't hit their expected attenuation, the will pitch a Lager yeast to bring it down.

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That makes no sense to me. Has he ever explained why that works?

Have you tried to rouse the yeast by stirring or rolling the fermenter tipped at 45 degrees? That can get some stuck fermentations going.

Attenuation is a strange thing. I have been brewing several AG beers with malt from my LHBS and my own cultured Wyeast 1099 Whitbread. Attenuation has ended in the ho-hum low 70's with FG 1.017 - 1.019. Then I got a mail order kit for an IPA (just malt and hops) from Austin Hombrew. To spiff it up a little I added a pound of Munich I had sitting around and a pound of Turbinado sugar (I was curious), again using the saved Whitbread yeast. Wham! FG = 1.010 from OG = 1.072. That's more than 86% attenuation!

What is going on here? I suppose it is possible that the LHBS malt was sub-standard, but they seem to have good turn-over on their malt. I've been mashing at 152 - 154 F, so no big difference there. I ferment at 68F consistently. I tend to believe it is the sugar, or maybe some minerals riding on the sugar, that helped the yeast to attenuate this much.

I am a very detail oriented brewer. I am never without my hydrometer and refractometer and use both during the entire process. I calculate preboil, midpoint and postboil gravities and adjust based on my mash efficiency. I really don't know what happened because I did a starter and after my second step up, I pitched at full krausen. I roused, I read stories to it but none of the old standbys worked.

As to why the lager yeast....I don't know but have an email sent and hope to hear a response.

Denny said:

That makes no sense to me. Has he ever explained why that works?

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Lager yeast has the ability to fully metabolize the wort sugars, giving lagers that super crisp/dry taste.