Stuck Ferment..... I think?

We brewed our 3rd batch of All-Grain 3 weeks ago. It's a Guinness Clone that was posted here. We hit all our Temps perfectly at dough in. Didn't have to adjust temps at all. We got a efficiency of 80% and pitched 4 packages of Nottingham yeast for a 10gallon batch (2 in each 6gallon carboy). Re-hydrated according to manufacture specs... Our OG was 1.052 right on target. Let it ferment in my chamber at 62* for 3 weeks. Airlock started within 12 hours and stopped after about a week. I never had a problem with fermentation of any of my PM batches, wine, or extract batches in the past so I decided to take a FG reading at bottling. Our FG was 1.028. I was looking more for a 1.016. After tasting the sample we decided to bottle regardless. Bottled with priming sugar to 2.2 volumes of Co. Should I be concerned with bottle bombs? I know there was a bad batch of Nottingham Yeast in the past. Could this be the problem? I'm lost.... Should i have not bottled and tried to raise temp in the chamber? I think this is the first and last time I'm gonna use dry yeast.


Thanks in advance!

Mike.......

Any time you have a question about your fermentation cycle, you should look for a consistent reading over a 3-day period. This usually ensures any activity will have completed.

Your temperatures could be off also, affecting attenuation - although that's a pretty big difference you posted there. I would imagine a Guinness clone would be a fairly med to med-low mash temp (150° - 152° F). If you are not using a high-quality, well-calibrated thermometer (and re-calibrating often), you could have some very different beers from what you are expecting. Make sure you are calibrating against a spirit thermometer from a reputable source.

Yup.... I think our mash temp was 151*F (I don't have the recipe in front of me). I know my thermometer was correct and we held our temps within a degree the whole mash. I know my hydrometer is correct. I tested it after taking my reading. I guess the lesson learned is take gravity readings no matter what. It boggles my mind why the ferment started and just stopped. I would think 3 weeks is enough time to let the yeasts finish up. Plus, I had one hell of a yeast cake at the bottom.

From OG of 1.052 to FG 1.028 is around 40% attenuation and suggest that something went wrong here, if the mash temp and SG readings are correct i would say you got a stuck fermentation but i can not really think of a reason for that, anyway you may be at risk of bottle bombs so i would monitor it closely (i would have a beer after 7-10 days in the bottle, if its fully carbonated i would have one every single day till its gone or till you are sure its not carbing any more, and with 3% abv drinking one a day shouldnt be a problem)

Would the viscosity of the wort change the reading? This was a somewhat thick syrup type wort.

Once they carbonate to my liking, would refrigerating the whole batch stop the yeast from working and carbonating the beer? I would definitely place them in some sort of container in the fridge just in case.

ColeBeer78 said:

Would the viscosity of the wort change the reading? This was a somewhat thick syrup type wort.

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Thats strange, i brew 1.1 OG RIS and i wouldnt say it was dense like syrup, i dont think wort should be viscous like that at least non of mine was. This could be the problem and i dont think it affected hydro reading but rather attenuation, what was the grain bill for that beer?

15 lbs Pale Malt, Maris Otter
4lbs Flaked Barley
2lbs Roasted Barley

The funny thing is I divided the 10 gallon batch into 2 6gallon carboys. Pitched 2 packets of Nottingham in each and got the same exact reading of 1.028 in both carboys.

I just opened a bottle and it's almost carb'd to my liking already. Only 2 days after bottling!!! I'm completely lost on this one. I had a bass ale clone brewed the same day and put in the same fermentation chamber with this beer and it hit it's FG.

Maybe not enough oxygen in the wort?

Just to follow up on this... It has been over 5 weeks conditioning in the bottle at 70* and haven't had one bottle bomb yet. Cracked one today and took a Gravity Reading with my refractometer out of curiosity. It have a gravity of 1.033.... Before priming sugar was added it was at 1.028. Its carb'd nicely and tastes great. Definitely one of the strangest batches I've had yet....

ColeBeer78 said:

Gravity Reading with my refractometer out of curiosity. It have a gravity of 1.033....

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The presence of alcohol screws up the refractometer unless you use some type of conversion chart or something to compensate (I don't have a refracto). Do you have a hydrometer to test with? Did you just recently switch to the refractometer with this batch?

Swampass is onto something. If you took gravity readings with your refractometer before fermentation and then also used your refractometer to take gravity readings after fermentation, the presence of alcohol in the finished beer will throw your numbers off.

I'm taking a stab here based on converting your OG and FG back into brix. If your OG was 1.052 that works out to about 12.86 brix. And assuming you took your FG using your refractometer, then an FG of 1.028 will have read about 7.06 brix.

I'm using Sean Terrill's refractometer FG calculator. Here's his website if your interested:
http://seanterrill.com/2012/01/06/refractometer-calculator/

Anyway, with an OG of 12.86 brix and an FG of 7.06 brix according to Sean's calculator, the actual gravity of your final beer is 1.0139 which is right around what you were looking for. So...good news...your beer is doing exactly what it's supposed to be doing.

P.S. there is a Basic Brewing Radio podcast with Sean where he talks about using a refractometer and the research he's been doing. Great stuff. You should check it out. It's available free in iTunes.

Nope.... Took my final gravity reading with my hydrometer. Just picked up a refractometer Recently. I didn't realize alcohol affects the reading with a refractometer. I guess I need to do some reading.