brew stuck at 1020

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Dutto said:
Er ... will not removing the top of a fermenter to "gently rouse the yeast" allow air to contact (aka oxygenate) the wort?
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Not if doing the stirring extremely gently. Thrashing it about will introduce oxygen.
Even just swirling the fermenter can rouse the yeast if the problem is stalling.

Rodcx500z said:
So anerobic is the ability to grow without oxygen at the right temp just like prefergins and clostridium welchi, so would bringing back to temp and re pitching help, over to you Foxy athumb..
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It depends on what your pitching viability was like, also your mash temperature, is it possible your mash temperature was to high?

A good read here from a home brewer who is also a biochemist, and don't reply to his blog with, "Pigs ****" as he is a lawyer as well.;)

https://www.morebeer.com/articles/oxygen_in_fermentation
 
Dutto said:
I still class it as "wort" and most brews require us to oxygenate the wort before we pitch the yeast.
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Before, yes, not after it has fermented already.
Dry yeast: it's sprinkled on top, so it's close to a lot of air already. One of the reasons liquid yeasts take ages to show some signs of life.
 
Dutto said:
Sorry, but gas diffuses in air at +/- 0.5 metres per second. Once you open the surface of a brew to the air then oxygen will enter the liquid.

Personally, I have never had a problem using the method I outlined.
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But we are talking of oxygen, getting through the co2! Then into the wort, it just doesn't work like that.
Read up on Henry's Law.
 
Rodcx500z said:
Twist in the tail, brought it in from the shed after 3 days it's started going again, what's going on
,
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Could be the warmer clime or the yeast, I tried some of that English Ale yeast from Crossmyloof Brewery that one you would swear was finished, knock the fermenter and it would just start going again.
 
foxy said:
But we are talking of oxygen, getting through the co2! Then into the wort, it just doesn't work like that.
Read up on Henry's Law.
Click to expand...

I presume that Henry never farted in a lift!

On one job, we put half a million cubic feet per day of methane gas through the vent system to prevent air diffusing into the vent system and causing an explosion!

Henry wasn’t on that job either!
 
foxy said:
But we are talking of oxygen, getting through the co2! Then into the wort, it just doesn't work like that.
Read up on Henry's Law.
Click to expand...

The gases will mix unless the fermentation vessel is under significant pressure and stays under pressure where only CO2 is in the headspace. If you are swirling this pressurised vessel, then O2 ingress will be negligible. As soon as you open it to stir though, the pressure gradients converge and the gases will mix readily. That O2 will dissolve into solution with no issues.

The only way beer can be protected from O2 in an open system is through vigorous fermentation (CO2 pressure expulsion higher than atmospheric pressure), or a physical barrier like a thick krausen. The idea of a CO2 blanket isn't feasible in the timescales of brewing. Yes it's heavier than O2, but it's also highly miscible.
 
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Brew_DD2 said:
The gases will mix unless the fermentation vessel is under significant pressure and stays under pressure where only CO2 is in the headspace. If you are swirling this pressurised vessel, then O2 ingress will be negligible. As soon as you open it to stir though, the pressure gradients converge and the gases will mix readily. That O2 will dissolve into solution with no issues.

The only way beer can be protected from O2 in an open system is through vigorous fermentation (CO2 pressure expulsion higher than atmospheric pressure), or a physical barrier like a thick krausen. The idea of a CO2 blanket isn't feasible in the timescales of brewing. Yes it's heavier they O2, but it's also highly miscible.
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That is why it is important to understand Henrys law, co2 inside and air outside the vessel are at 1 atmosphere pressure I can safely take off the lid of a fermenter and dry hop, taking off the lid off at an equal pressure is not going to cause a surge of air rushing into the vessel. Oxygen is in round figures is 20% of air, if the yeast can be roused any ingress of oxygen which will be extremely minimal will be dispersed, by the fermentation process it will not be taken up in the wort.
Thrashing the wort at the stage of fermentation which Rodcdx500z beer is at will cause oxidation.
https://beerandwinejournal.com/stuck-ferment-2/
 
foxy said:
That is why it is important to understand Henrys law, co2 inside and air outside the vessel are at 1 atmosphere pressure I can safely take off the lid of a fermenter and dry hop, taking off the lid off at an equal pressure is not going to cause a surge of air rushing into the vessel. Oxygen is in round figures is 20% of air, if the yeast can be roused any ingress of oxygen which will be extremely minimal will be dispersed, by the fermentation process it will not be taken up in the wort.
Thrashing the wort at the stage of fermentation which Rodcdx500z beer is at will cause oxidation.
https://beerandwinejournal.com/stuck-ferment-2/
Click to expand...

I understand Henry's Law fine thanks. You spoke about taking the lid off and stirring. That will introduce oxygen, but obviously whipping it up will do so to a greater extent and I would advocate neither. Even dry hopping you will introduce some oxygen. Whether this will be detectable in the final beer is absolutely up for debate, but the O2 will be there.
 
Brew_DD2 said:
I understand Henry's Law fine thanks. You spoke about taking the lid off and stirring. That will introduce oxygen, but obviously whipping it up will do so to a greater extent and I would advocate neither. Even dry hopping you will introduce some oxygen. Whether this will be detectable in the final beer is absolutely up for debate, but the O2 will be there.
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Here is a simple explanation about Henrys law, this is in 25 C water. In wort which is cooler, say 18 C and a higher density than water makes it far more unattractive to oxygen molecules, not unless you stir oxygen into the wort by splashing.
So with a stuck mash what would you do, take the lid off and thrash the wort, or gently stir without splashing, which is the go to remedy or have you got a better solution?
Dry hopping is generally done with a degree or two Plato left to go so there will be no oxygen ingress whatsoever. Whatever goes in with the hops is driven out by the fermentation.
https://www.khanacademy.org/science...ystem/gas-exchange-jv/v/o2-and-co2-solubility
 
Don't need to teach me to suck eggs pal. I'd be looking to raise the temperature or swirl the fermenter. Even still you're getting oxygen ingress unless you are doing everything in a closed, pressurised environment.

Anyways, it's largely academic given how beer is usually transferred in the homebrewing community. Far more oxygen exposure at racking that will be of potential detriment to the finished beer.
 
Brew_DD2 said:
Don't need to teach me to suck eggs pal. I'd be looking to raise the temperature or swirl the fermenter.
Anyways, it's largely academic given how beer is usually transferred in the homebrewing community. Far more oxygen exposure at racking that will be of potential detriment to the finished beer.
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As I said in post 18.
Any oxygen which on the slightest chance may have entered the wort will be driven off by resumption of fermentation.
Transferring into a bottling bucket the bottle fermentation will use the oxygen in the beer but not the oxygen in the head space, keeping the beer below 20 C gives it a longer shelf life before the oxygen makes its way into the beer.
 
Gently stirring with a sanitised spoon is the correct method.

@Dutto, your technique would be sound for a stuck fermentation at a much higher gravity, i.e. closer to OG. As already mentioned, I'd be wary of introducing oxygen to the beer via aggressive stirring when you're likely within 0.010 of desired FG.

I've thrashed the death out of a lager which stalled about 48hours into fermentation, but the OG had barely shifted - meaning what was in the bucket was definitely wort rather than beer. Oxygen and wort is good, oxygen and beer not so much...
 
When does wort change to beer?
My rule of thumb answer would be when the aerobic yeast multiplication phase is over and the yeast has started to produce alcohol even though the concentration will be small. In other words its very early on in the primary fermentation phase.
Anyone?
 
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