Can we dispel the myth of the 'CO2 Blanket' ?

[BrewZer]

At least we're talking about a CO2 duvet, not bidet, even if those might also be underrated..

I forgot where I was going with this , , , sorry. ;]

There is no "P" in CO2

 

[Zadkiel]

The lifetime of the "blanket" is minutes if the cover is taken off of a bucket fermenter.

I strongly disagree, and I have trouble reconciling you saying this with you liking my post back on page 1 about fluid dynamics, BUT thankfully, despite disagreeing on this, we both agree on the more important fact, which is that regardless of what happens to the CO2, the O2 ingress is instantly significant.

 

[sibelman]

Oxygen in fermenter (after "primary" fermentation) bad. Frankenstein no like oxygen in fermenter. Frankenstein like blanket.

 

[kohalajohn]

Look. CO2 is clearly an effective protective blanket, and in three scenarios.

First, have Muhammed Ali do the dry hopping.

"I'm so fast! I'm so fast I turn off the light and I'm in bed before the room gets dark!. I"m fast!"

Second, just do your brewing on a neutron star. Gravity is 10 to the 11 decimals earth gravity. The blanket of CO2 will be dense enough to resist diffusion. And the lack of an atmosphere will also help.

Third, use a hop bong.

 

[Zadkiel]

Second, just do your brewing on a neutron star. Gravity is 10 to the 11 decimals earth gravity. The blanket of CO2 will be dense enough to resist diffusion. And the lack of an atmosphere will also help.

Don't be ridiculous. An extension cable to your fermentation fridge wouldn't work over that long of a length. DUH!

 

[betarhoalphadelta]

The lifetime of the "blanket" is minutes if the cover is taken off of a bucket fermenter. But once you take the cover off, O2 gets into the top of the headspace in less than a second, and the O2 concentration near the top of the fermenter increases rapidly from there, even if very little O2 has made it to the surface of the beer. When you put the lid back on, all of the O2 that entered the headspace is still in the fermenter, and significant amounts will diffuse to the surface of the beer in minutes. The O2 at the surface of the beer will start diffusing into the beer, and if you don't have ongoing yeast activity to consume the O2 by bio-chemical means, it will start to oxidize beer components.

The oxidation is slow compared to the interdiffusion of O2 and CO2, but as the oxidation occurs, the concentration of free O2 in the beer drops, allowing more O2 to diffuse into the beer from the headspace.

If there was no oxidation or O2 consumption going on, then eventually the O2 concentration in the beer would reach equilibrium with the O2 partial pressure in the headspace. But if there is oxidation or consumption then the O2 concentration in the beer doesn't reach equilibrium with the O2 in the headspace, and eventually essentially all of the O2 in the headspace will end up in the beer.

Brew on

So would the real answer be not that you have to dry hop and put the lid back on within 1 second, but merely that you should dry hop before you've reached 100% complete fermentation? Because if you still have ongoing fermentation activity, the yeast will still be able to handle the O2...

Or am I off base here...

 

[Yooper]

So would the real answer be not that you have to dry hop and put the lid back on within 1 second, but merely that you should dry hop before you've reached 100% complete fermentation? Because if you still have ongoing fermentation activity, the yeast will still be able to handle the O2...

Or am I off base here...

Unfortunately, it's not that simple. Remember, gasses readily mix. So just opening the fermenter allows oxygen ingress (and it's never 100% co2 anyway).

If there really was a CO2 blanket, we'd all die in our sleep every single night.

 

[betarhoalphadelta]

Unfortunately, it's not that simple. Remember, gasses readily mix. So just opening the fermenter allows oxygen ingress (and it's never 100% co2 anyway).

Right, but what Doug was pointing out (the bit that I bolded) was that as long as there's still yeast activity, the yeast might consume any oxygen that has entered the fermenter.

Obv this can be dependent on a lot of things. I ferment larger (10 gal) batches in a fermenter with a very narrow opening, so I'll have more volume of beer, less oxygen ingress, and more yeast to do the job... Whereas someone doing 5 gal batches in a bucket will have a lot more oxygen ingress because of they large opening, 1/2 the volume of beer which is then effectively double the ppm uptake that the yeast have to deal with, and less yeast to handle it. So on a relative level, it might mean I'm more safe than the person fermenting 5 gallons in buckets.

But ignore the quantities involved to think of it more theortically... The question would be that if you're only, say, 80% of the way to your target FG, does that mean the yeast is still capable of cleaning up some/all of the O2 that you might introduce during dry hopping?