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

[Snuffy]

That's a good system.

For me, rather than use a hop bong, I have been using a hyperbaric chamber. I crawl inside the chamber, bringing the fermenter with me. I have the chamber filled with co2.

When I open the fermenter and add the hops, the entire environment is co2, so there is zero oxygen ingress.

I am wearing scuba gear so I can breathe in the chamber.

Photo attached.

Do you vary your diet at all the day before?

 

[VikeMan]

That's how Kegland says to do it. @Bobby_M sold me the bong and his advice was to do it with the prv open and a constant flow, so that is what I do.

We are guessing here, as we can't see what is happening. But Bobby's method makes sense to me.

Perhaps you could ask to see Bobby's calculations and/or measurements.

For comparison, most people purging kegs use a series of pressurize/release cycles. I haven't calculated the efficiency of the "continuous flow" method, but I'd be willing to bet a beer or two that it's more expensive to reach a given O2 concentration (in terms of total CO2 needed) than the pressurize/release method. @doug293cz did you take a whack at this before?

The pressurize/release is method easy enough to model, and easier with a cheat sheet. No guessing.

 

[Zadkiel]

small nitpick but that seems to be calculating ppm in the bong, not in the headspace. When the bong is opened there will be a dilution based on the volume of CO2 in the headspace and the Volume of the gasses in the hop bong, which is going to be different for each and every setup so not feasible to account for - but you labelled it as ppm in headspace so I'm being pedantic

Maths looks good to me, my napkin math got 4.5% O2 earlier in the thread for 3 cycles at 10 PSI (as that's what I read in the fermzilla bong instructions) and that's what you get there too (well, closer to 4.4%, but I was using appoximations: 21% O2 and 15PSI atmospheric pressure, which would account for my slight inaccuracy)

 

[BrewZer]

Have any calculations taken into account the embedded O2 present in the hops pellets/cones themselves, and how, exactly would you calculate that?

Yes, your hops probably came to you in a nitrogen-filled vacuum pack, but as soon as you opened it, all those nasty O2 molecules rushed in and contaminated the pellets.

Perhaps the ritual should include an O2 purge cycle for the hops prior to putting them into the hop dropper...? You know, like 24 hours bathed in a bowl full of dry ice or something...

 

[Zadkiel]

Yes, your hops probably came to you in a nitrogen-filled vacuum pack, but as soon as you opened it, all those nasty O2 molecules rushed in and contaminated the pellets.

You aren't opening your hops in a vacuum sealed chamber? Amateur!

 

[VikeMan]

small nitpick but that seems to be calculating ppm in the bong, not in the headspace. When the bong is opened there will be a dilution based on the volume of CO2 in the headspace and the Volume of the gasses in the hop bong, which is going to be different for each and every setup so not feasible to account for - but you labelled it as ppm in headspace so I'm being pedantic

In the "bong," the total volume is the "headspace," for the purposes of calculation. Yes, it's labeled as "headspace" because it was originally made for keg purge calculations. But it applies equally to any enclosed gas space.

 

[Zadkiel]

I guess we're just using headspace differently, to me the common use of headspace is the area of gasses inside the fermenter. Yes, technically the gasses in the sealed bong is also a headspace, but I think anyone reading your chart would assume incorrectly But it's your own tool.

 

[VikeMan]

Have any calculations taken into account the embedded O2 present in the hops pellets/cones themselves, and how, exactly would you calculate that?

I know you're joking, but just for the record... there's no need (even a theoretical one) to calculate that. The hops themselves take up some space, and thus reduce the volume of the gas space, but the volume doesn't matter (for the purge/release calculation).

 

[Brockness Monster]

Limnic Eruptions, perhaps the largest of all CO2 blankets. Once in a lifetime opportunity for the avid LoDO brewer

And yes, before someone points something out, I understand the CO2 emission during a Limnic Eruption is colder than atmospheric temps which causes it to fall and suffocate ungodly amounts of humans and livestock. this was meant as a joke, don't @ me.

 

[VikeMan]

Yes, technically the gasses in the sealed bong is also a headspace, but I think anyone reading your chart would assume incorrectly But it's your own tool.

I suppose they could assume whatever they want in this case, but the result would be the same regardless. The O2 concentration left in the whole enclosed part of the hop dropper will be the same throughout... top, bottom, middle, above or below the injection point. All the same.

 

[Zadkiel]

Yes, it's labeled as "headspace" because it was originally made for keg purge calculations.

Oh, right, I see now. You built this in the context of a different simulation where that 'headspace' wasn't then being opened up to another volume. Sorry I was looking at the chart purely in the context of hop bong into fermenter. Got it.

 

[BeerNsteadofH2O]

with all this rampant running 02 spoiling everyone's beer it's Time to take up knitting

 

[kohalajohn]

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

I see. Diffusion is happening twice. At first, the principle of equilibrium causes the two gases in the headspace to diffuse into each other. So what? Why care?

We care because equilibrium is still not reached. Although the oxygen in the headspace is now less concentrated, all of it is still there, and must seek equilibrium with components in the beer.

 

[mac_1103]

I'd only ever seen, watching various different brewing videos on youtube, the 'cycle the PRV 3-4 times' method, which I'm suspicious of.

Yeah, that is obviously woefully inadequate.

 

[kohalajohn]

A few people here, myself included, have questioned why oxygen ingress is suddenly a concern.

I think it's because we now have tools to deal with it. Hop bongs and closed transfers.

Similarly, Statin drugs to treat high cholesterol did not appear until the end of the eighties. Then, starting in the nineties, doctors were talking about cholesterol problems. Because now they had a tool for it.

 

[mac_1103]

A few people here, myself included, have questioned why oxygen ingress is suddenly a concern.

Suddenly?

Similarly, Statin drugs to treat high cholesterol did not appear until the end of the eighties. Then, starting in the nineties, doctors were talking about cholesterol problems. Because now they had a tool for it.

Doctors were talking about cholesterol long before statins were developed. To members of my family at least. Anyone who survived a heart attack was advised to basically eliminate fat, and especially cholesterol, from their diet. The fact that this advice wasn't particularly effective doesn't mean that it wasn't given.

 

[kohalajohn]

I remember back then. Pre drugs, the doctors were just finger wagging at patients, and it didn't accomplish much. But when effective drugs arrived on the scene, then the doctors got much more busy.

I think same thing with anti depressants. This was before my time, but my parents said that when the anti depressant drugs first same out, it seemed like a lot of patients were being diagnosed with depression.

 

[mac_1103]

It is certainly true that a lot of drugs are overprescribed. But the drugs never would have been developed if the problems hadn't been recognized in the first place.

A little searching and browsing on this site will reveal some twenty year old posts talking about oxidation.

 

[VikeMan]

A few people here, myself included, have questioned why oxygen ingress is suddenly a concern.

Define suddenly. The hardcore LODO crowd has been active since 2014, possibly earlier. And they weren't the first ones to combat O2 ingress. Keg purging has been a thing for at least as long as I've been kegging (2009-ish?), and I certainly didn't invent it. And it was earlier than that people started eliminating secondaries, because of O2.

ETA: Almost forgot about the esteemed Charlie Bamforth, who around that era made it a point to tell people not to worry about hot side aeration. There must have been a significant number of HSA believers for him to feel he had to counteract it. Fast forward to 2017, by which time Charlie had written "Freshness," which contained (wait for it...) advice about how to avoid HSA.