Stuck fermentation-- how can I rescue it?

[nyoksol]

Doing my first ever brew-- 5 gal red ale with wlp001. My OG was 1.057, and the recipe's supposed to end up around ~1.010 after 14 days or so. Exciting!

Well, it's been 11 days, and fermentation has definitely stopped for at least a couple days now around 1.025. I have an automatic chiller system I home-rigged with some copper piping, and I've kept the fermentation temp at a chill 66±2°F. Tried raising it up to 68 a few days ago, and minus pumping hot water into my cooling system it's not generating any heat on its own, and hasn't for a while.

Reason I think its stuck, about two days ago I dumped a ton of trub + some beer into a mason jar to reuse, and ended up leaving it outside (but still sealed) by accident. When I found it again, it had started bubbling vigorously, and had a strong krausen layer on top. I checked the gravity of this, and it had dropped down to 1.020; the main was still at 1.025.

Two things I can think of:
1. One, my cooling system is copper tubing that's resting in the fermenting chamber itself, in contact with the beer. I know that SS is generally preferred, but I already had my hands on the copper, and I figured I'd try, especially once I found out older ferment vessels used to be made of copper. I'm wondering if the copper's anti-microbial properties are somehow killing off the yeast, though the same amount of copper would still be in the beer after putting it in the mason jar if dissolved ions were the issue (methinks).
2. Two, maybe the yeast ran out of oxygen, and pouring it into a jar reoxygenated/agitated the yeast enough to get things going again? I'm really hesitant to do anything to oxygenate this late in fermentation, especially if it might screw things up. I did end up dumping the krausen/yeast in and stirring just a little bit in the hopes of triggering something in the main chamber (after finally installing my trub catch correctly), but its too early to tell if that did anything.

I honestly can't think of why this is happening or what I can do to fix it . The temperature I had it fermenting at was on the chill side but still within the wlp001 range. Is there anything else I could do to try to retrigger fermentation?

- Nyoksol

 

[IslandLizard]

Well, it's been 11 days, and fermentation has definitely stopped for at least a couple days now around 1.025.

What instrument are you using to measure the gravity of your fermenting beer?

 

[nyoksol]

What instrument are you using to measure the gravity of your fermenting beer?

Refractometer. I don't really have a comparison for what uncarbonated beer is supposed to taste like, but the stuff in the main fermenter tasted really thin and watery. The stuff that had started fermenting again in the mason jar was noticeably fuller-tasting-- plus a ton of krausen.

 

[IslandLizard]

Refractometer.

Thanks for the confirmation, that's what I was thinking.
When using a refractometer, you'll need to use a calculator to arrive at the real SG/FG, to correct for alcohol in your sample.

Such as this one:
https://www.brewersfriend.com/refractometer-calculator/Use Part II.
You'll need to input your original gravity (OG) and the current gravity as measured with your refractometer.

That will give you a much closer true SG/FG.

 

[IslandLizard]

When fermentation is about completed, it starts to slow down, there's less sugar left to ferment.

When that phase in time has reached, it's advised to move the fermenter to a somewhat warmer place (5-7°F higher), or keep her warmer (e.g., with a heating pad or so), so she can finish out. That also allows her to condition the beer, metabolizing many fermentation byproducts, making for a better, cleaner tasting beer.

I recommend reading John Palmer's How to Brew, 4th Ed.

 

[IslandLizard]

about two days ago I dumped a ton of trub + some beer into a mason jar to reuse

How did you "dump" that?
Was that done in a sanitary way?

and ended up leaving it outside (but still sealed) by accident. When I found it again, it had started bubbling vigorously, and had a strong krausen layer on top.

It must have been a warm enough day for it to resume...

I checked the gravity of this, and it had dropped down to 1.020; the main was still at 1.025.

Well, that tells us your main batch of beer wasn't quite finished... it still had a few points to go.
If it's not completely done fermenting, that could become an issue when bottled.

Depending on how and when you dumped that "trub," it likely contains much good yeast.

I did end up dumping the krausen/yeast in and stirring just a little bit in the hopes of triggering something in the main chamber

As long as everything was done in a sanitary fashion, that should be alright.
How long ago was that?
Did you see any more fermentation signs after dumping it back in?

 

[nyoksol]

Yeah, everything was sanitary. It's been about 24 hours and there's some light bubbling, but the temperature dropped back down to ambient, so I suppose I should just try to warm it up by a few degrees.

I can't believe I forgot about the conversion factor for the refractometer no amount of reading ever prepares you for really getting your hands wet. Thanks for the help!

 

[IslandLizard]

Yeah, everything was sanitary.

That's most important.

t's been about 24 hours and there's some light bubbling, but the temperature dropped back down to ambient, so I suppose I should just try to warm it up by a few degrees.

Yeah, try to at least to keep temps (more) constant, sudden (such as overnight) temps drops can stall a fermentation.

2. Two, maybe the yeast ran out of oxygen,

Yeast only needs oxygen during her (aerobic) growing (multiplying) phase.
Once she starts fermenting (anaerobic phase) any oxygen that remains will be blown out with the CO2.

Any oxygen added after her growth phase won't be used up, and could cause oxidation (staling reactions) in the beer, especially when CO2 production is low or nonexistent (toward the end of active fermentation). That's why we need to keep oxygen away from the beer, once fermentation has started.

 

[dmtaylor]

Reason I think its stuck, about two days ago I dumped a ton of trub + some beer into a mason jar to reuse, and ended up leaving it outside (but still sealed) by accident. When I found it again, it had started bubbling vigorously, and had a strong krausen layer on top. I checked the gravity of this, and it had dropped down to 1.020; the main was still at 1.025.

The "1.020" sample might be contaminated. Knowing that you used refractometer, the SG is actually below 1.000. Hmm......

 

[IslandLizard]

The "1.020" sample might be contaminated. Knowing that you used refractometer, the SG is actually below 1.000. Hmm......

Hah! I was wondering about those 1.020 / 1.025 "FG" numbers, but didn't check them on the ABV calculator.
We usually get 1.040-some readings when using a refractometer to poll FG.

 

[nyoksol]

The "1.020" sample might be contaminated. Knowing that you used refractometer, the SG is actually below 1.000. Hmm......

Very well could be yeast that had been floating around... I tried my best to get through the krausen for a clean sample, but that was definitely not a perfect sample. The 1.025 from the main ferment was sampled from the top, and that's been really consistent for a few days now. My refractometer has a correction factor of 1.06, so plugging in those numbers comes out looking a bit more reasonable...

Minus just the raw numbers (I'm definitely not forgetting about the corrections after this!), is there a way to gauge the final taste post-ferment but pre-carbonation? Does the flavor profile change significantly ('thicken' and develop complexity) as it continues to condition, and is there a way to gauge how it might change, or is it really just being open to an adventure in the unknown?

 

[dmtaylor]

Minus just the raw numbers (I'm definitely not forgetting about the corrections after this!), is there a way to gauge the final taste post-ferment but pre-carbonation? Does the flavor profile change significantly ('thicken' and develop complexity) as it continues to condition, and is there a way to gauge how it might change, or is it really just being open to an adventure in the unknown?

If the beer tastes good before it's carbonated, you can have high confidence that it will turn out great after conditioning. If it tastes a little odd before carbonation, it might just need time for the yeast to clean up after themselves and should hopefully improve after conditioning and carbonation. If it tastes downright BAD before carbonation... it will likely still turn out OK but there are no guarantees.

Common flavors while beer is still young and "green" include sulfur (eggs, farts), diacetyl (butter, butterscotch), yeast (dough, liver), sometimes extra esters (fruity) and higher alcohols (powerful alcohol). All these things should mellow out after a few weeks of aging, as well any characteristics from late hop additions. Oxidation, IF excessive, can begin to rear its ugly head after a few weeks as well, which can add flavors like caramel, paper, cardboard, or can simply dull all other flavors. So... it's not an adventure into the unknown usually, but the effects are very complex and can be difficult to predict with precision, other than the rules of thumb I stated first. What I like to find is that it already tastes very good before conditioning, then I know the odds are great that I will have a great or even outstandingly excellent finished product.