Odd AG/FG question.

[DavesNotHere]

Not sure if this is an all-grain, or fermentation forum question... I tried my first all grain brew a few weeks ago. I was using the Atonement Brown Porter AG recipe... I used a braided hose style mash tun...

When I was done, my OG was just a bit below the recipe OG. Once I cooled my wort down to 70F, my gravity was 1.054... i pitched the WYeast smackpack... it had been swelling for about 5 hours... Then, a day later, the fermentation appeared to be completed. The gravity now was 1.034. According to the recipe, it should be 1.012... I let it sit for a week... no change. Still 1.034. I figured I did something wrong, and dumped it out, and started over.

I completed the copper manifold mash tun... re-brewed the same recipe... Used a new, digital thermometer to ensure temperatures.... Took my time draining after the mash, and single infusion batch sparge....

The second attempt yielded an OG of 1.062... However, after a week, the gravity is still about 1.032.... I'll keep an eye on it, but I don't anticipate it will drop much, if at all from this point. It tastes alright, but much lower ABV than anticipated...

Any suggestions on a stuck/stopped fermentation? Should I pitch a second pack of yeast? Based on the OG, it would appear that I extracted a large amount of sugars... but why won't it get any lower?

Thanks.

 

[boist]

There are several things to look at:

First, it would not hurt to pitch more yeast (another pack). It would also be a good idea to get a pack from a different source/batch in case you have some bad yeast.

Second, look at your temperature. Too cold, and yeast goes dormant and wont ferment. Too hot and yeast gets too stressed and can quit on you.

Third, look at mash temperature. This is kind of a long shot, considering the discrepancy you're describing, but the warmer your mash temp, the less fermentable your wort - you will have more residual sugars (higher FG, lower ABV) after fermentation. Make sure your thermometer is calibrated (do a side-by-side measurement with a regular thermometer).

Fourth, you'd notice that the recipe goes from 1.048 to 1.012 which is 36 point difference. You went from 1.062 to 1.032 which is 30. Not that far off it terms of ABV. I'd look at actual efficiency as compared to the reference recipe, and also if your yeast is a bit different in terms of attenuation.

And finally, don't dump it. Go through with it, bottle it, age it, taste it. It may not be exactly to spec, but is it good? Bottom line is that that's what counts. Once you know what it tastes like when you brew it, you can fiddle with the recipe to adjust it to your liking.

 

[ChandlerBang]

I'm new to AG myself, so i can't speak to the issue really. But, dude, never dump your beer. If it has an infection or makes you throw up when you taste it are the only possible exceptions to that rule. There are dozens of things to try to fix it (or in a lot of cases there isn't anything wrong with it). You came to the right place.

 

[rorygilmore]

The most obvious suspect is something is going on with your mash temps... give a detailed step-by-step report on your mash process and maybe we'll be able to pick something out. Also, follow the advice given for calibrating your thermometer (and it wouldn't hurt to check they hydrometer as well).

My suggestion for your next beer would be a saison with wyeast 3711 and a fairly simple grain bill. That yeast is a monster and if you have a stuck fermentation you'll at least know that it's something in your process and not the yeast.

Another suspect could be the brown malt called for in your recipe... maybe it was accidentally switched out with a dark crystal malt or for whatever reason is giving you a ton of unfermetables - it's a long shot but that could explain the high FG.

 

[Rockape66]

Since the recipe calls for brown malt, what kind of water are you using. Brown malt calls for significant alkalinity in your water to achieve proper wort pH. Another thing is; how well did you aerate your wort?

 

[boist]

oooh, good call on the aeration point. I was assuming that since he's new at this he just dumped the kettle in to the bucket, splash and all, but definitely worth asking.

BTW, I should clarify something about my original response: It wouldn't hurt to use a second pack of yeast the next time you brew. I wouldn't necessarily add one to a semi-fermented beer. If the problem is not the yeast, but the wort, then adding more yeast can just give your beer a yeasty taste without actually improving the situation.

 

[afr0byte]

Not sure if this is an all-grain, or fermentation forum question... I tried my first all grain brew a few weeks ago. I was using the Atonement Brown Porter AG recipe... I used a braided hose style mash tun...

When I was done, my OG was just a bit below the recipe OG. Once I cooled my wort down to 70F, my gravity was 1.054... i pitched the WYeast smackpack... it had been swelling for about 5 hours... Then, a day later, the fermentation appeared to be completed. The gravity now was 1.034. According to the recipe, it should be 1.012... I let it sit for a week... no change. Still 1.034. I figured I did something wrong, and dumped it out, and started over.

I completed the copper manifold mash tun... re-brewed the same recipe... Used a new, digital thermometer to ensure temperatures.... Took my time draining after the mash, and single infusion batch sparge....

The second attempt yielded an OG of 1.062... However, after a week, the gravity is still about 1.032.... I'll keep an eye on it, but I don't anticipate it will drop much, if at all from this point. It tastes alright, but much lower ABV than anticipated...

Any suggestions on a stuck/stopped fermentation? Should I pitch a second pack of yeast? Based on the OG, it would appear that I extracted a large amount of sugars... but why won't it get any lower?

Thanks.

You're not taking your FG reading with a refractometer, are you? That would, or at least could,explain the unusually high FG reading.

 

[DavesNotHere]

You're not taking your FG reading with a refractometer, are you? That would, or at least could,explain the unusually high FG reading.

No. I used a hydrometer, and i've done about 7 other batches (all extract), using the same equipment. I've never noticed any discrepancies with OG/FG readings. I have some friends who just bought refractometers. I'l check out borrowing one of theirs.

And finally, don't dump it. Go through with it, bottle it, age it, taste it. It may not be exactly to spec, but is it good? Bottom line is that that's what counts

As for this point, the first and only batch I have ever dumped, was the first AG batch. I tasted it, and had a friend taste as well. We both decided there was something wrong in the process on that batch, and I decided to start over.

The second AG batch using the same recipe, but with grains bought from a different LHBS, tastes a lot more like a porter, even at this early stage.

As for the grain bill, I used UK Pale (Maris Otter), UK Brown, and US Black Patent.

I know the problem the first time was a crappy thermometer that I couldn't read. The second time, I am sure I was spot on w/ the mash temps. Definitely not over. I know a few degrees can make a big difference... so i've been looking online to find a good one. Any suggestions?