Fermentation - Very poor attenuation after 3 weeks - Help

What did you mash at? Also, give recipe details. I'd likely going for bumping temp to 72 F-ish and rouse twice a day. If you get nothing, blending my be best option; although that is a damn not of sugars remaining.

 

One possibility is that you didn't get good conversion of starches to sugar. Could be you messed up the decoction, could be that your mash temps were off, that you just weren't exposing all that grist (especially all the adjunct grains) to enough enzymes in the short time window, and you ended up with a lot of solubilized by uncoverted starch?

Sidenote: Although I am reluctant to blame the decoction if it is properly done, I have to ask, why? The impact of decoction is pretty subtle, and I would guess that 3#s of crystal malt and 3.67#s of roasted grains is going to swamp out the subtly.

The other possibility (besides conversion problems) is that your yeast are challenged by the fermentation conditions of too much sugar -- too small a pitch, not enough oxygen, and, for some strains, temp control -- are the contributing factors.

To evaluate the issue, you could do a force fermentation test -- pull a small sample of the beer, pitch a goodly amount of healthy yeast in it, and see if they can ferment the beer.

• If the yeast can ferment this, you know that you need a really big healthy pitch to finish the remaining beer.
• If not, your beer is done. It will not end up where you want it to be.

 

I agree with pweis909, the decoction in my mind is a strange choice on this one. Lagers it makes sense due to the subtle malt qualities, but stouts are not short on that for sure.

You had mentioned wort aeration was OK, how did you do this? Typically with beers this big, you usually want the ability to hit it with pure O2.

I brewed a huge RIS back in May (which is going on tap in the next few weeks here). OG was 1.116 and FG of 1.031 (11.5% ABV).

When chilled to temp, I hit the beer with 2mins of pure O2. Then again 8hrs later for a second dose. Took 10 days to hit FG from the time I had pitched the yeast (2 packs of US-05, rehydrated for 5-gal). I mashed at 152F for 75mins. Next time, I would mash at probably 148-150F to dry it out even further.

My suggestion to kick start fermentation, if there are any sugars to be eaten, is to create a bigger starter of a yeast such as WY-1056 and pitch it into the beer at high krausen. That will be your best chance at getting something going again.

 

Force fermenting as @pweis909 suggests is the way to go. If a smack pack of chico can ferment out a quart of wort/beer then there is hope. If not, thats alot of beer to dump.

 

Did you also use a refractometer for all of the gravity readings? If so, did you run the OG and "FG" reading through a refractometer calculator together?

If you're using the built in specific gravity scale (normally on the right side of a refractometer display), it will be a little bit of for OG and way off for subsequent readings.