Any concerns with an oversized conical?

[brewguyver]

I've scaled back my brewing lately, and decided to get a small (7 gal) stainless conical from the bru-gear kickstarter. The 7 gal wasn't economical, so they're giving everyone who bought one a 14 instead. Awesome ... except I'm not planning on batches over 6 gallons very often.

Will the offgassed CO2 just blanket the wort, or should I take protective measures? Also, should I be more careful with the pure O2 since there is more head space for it to collect in?

Thanks all!

 

[sikkingj]

You will be fine - as you said the co2from the fermentation process has got you covered...


Sent from the window of an airplane...

 

[estricklin]

Bigger really is better....

 

[ckelly999]

CO2 is heavier than air, you're covered (see what I did there?)

 

[ajdelange]

That actually only matters at first. If there is any air left in the headspace (i.e. the CO2 evolution from the fermentation does not push it all out) it will diffuse (or get mixed via convection driven by the chill bands) through the volume of CO2 and reach the beer. If you have had vigorous fermentation with the CO2 bucket gurgling merrily away for a couple of days then you should have no worry as the O2 will have been pushed out.

 

[dmcman73]

You'll be fine, if you really have any concerns about O2 then you can purge the conical with CO2 prior to filling it but the fermenting process will take care of that for you.

 

[chickypad]

What are you planning for temp control? That's a potential issue I see. For example some cooling systems have a chiller coil that attaches to the lid, it may not be submerged if the conical is underfilled. On my 14 gal morebeer conical the chilling element is on the vertical side, you need at least 8-9 gal to be in contact with the inner wall there. Or if you're going the fridge/freezer route it would be easier to fit a smaller conical.

 

[kevink]

CO2 is heavier than air, you're covered (see what I did there?)

This is a really common misconception in homebrewing. It is simply not true, yet every few days you see a similar post. If you have air and CO2 in a fermenter and the beer is not producing enough CO2 to completely displace the air, then the air will mix with the CO2. The CO2 will not form a "blanket" and prevent the air from reaching the beer.

If it were true, gas mix cylinders, such as an argon/CO2 cylinder for MIG welding, would separate and have to be shaken before use. If it were true, if you closed an empty 5 gallon bucket containing air (which is basically nitrogen, oxygen, argon, and CO2), the CO2 would sink to the bottom. This just does not happen because the molecules are in constant motion. Because they are in constant motion, the concentrations of the gasses will be equal in all parts of the bucket.

Would it stop me from using a a large fermenter for a small batch? Probably not, but I would not open the fermenter during the tail end of fermentation and I would push it out with CO2 for packaging. I would take gravity readings through a small hole or sample port. If I had to remove the lid to dry hop or something, I would probably purge the headspace with CO2 after adding the hops if fermentation was over.

 

[augiedoggy]

This is a really common misconception in homebrewing. It is simply not true, yet every few days you see a similar post. If you have air and CO2 in a fermenter and the beer is not producing enough CO2 to completely displace the air, then the air will mix with the CO2. The CO2 will not form a "blanket" and prevent the air from reaching the beer.

If it were true, gas mix cylinders, such as an argon/CO2 cylinder for MIG welding, would separate and have to be shaken before use. If it were true, if you closed an empty 5 gallon bucket containing air (which is basically nitrogen, oxygen, argon, and CO2), the CO2 would sink to the bottom. This just does not happen because the molecules are in constant motion. Because they are in constant motion, the concentrations of the gasses will be equal in all parts of the bucket.

Would it stop me from using a a large fermenter for a small batch? Probably not, but I would not open the fermenter during the tail end of fermentation and I would push it out with CO2 for packaging. I would take gravity readings through a small hole or sample port. If I had to remove the lid to dry hop or something, I would probably purge the headspace with CO2 after adding the hops if fermentation was over.

The thing is, in a welding tank those gases were already mixed when they were put in the tank under force and pressure and the c02 wasnt being produced in the tank like it is when its coming out of the beer at the bottom of a conical... because of this I believe it does tend to stay on the surface of the beer and form a blanket

 

[kevink]

It is independent of pressure. If two or more gasses share the same vessel, the molecules will evenly distribute themselves inside the vessel. There will be no layering.

 

[ajdelange]

The thing is, in a welding tank those gases were already mixed when they were put in the tank under force and pressure and the c02 wasnt being produced in the tank like it is when its coming out of the beer at the bottom of a conical... because of this I believe it does tend to stay on the surface of the beer and form a blanket

No. As I explained in #5 at first the heavier gas can displace the lighter one but the two gasses intermix over time. Each gas molecule has a velocity proportional to sqrt(T/m) where T is the (absolute) temperature and m the mass of the gas molecule thus air moves into the CO2 'blanket' faster than the CO2 molecules move into the air space but the second law of thermodynamics requires that at equilibrium the two will be intermixed uniformly (i.e. each will be uniformly dispersed throughout the entire volume of the fermenter). There is some question as to how long it takes to reach equilibrium and as long as gas is being evolved by the beer equilibrium can never be reached so you are safe. Once gas evolution stops, however, diffusion begins (it goes on all the time but when gas evolution stops it dominates). In the headspace of a small cylindroconical at reasonable temperature you might have a couple of hours.

illustrates what happens quite nicely. I first saw this when someone else posted it here in another thread on this very subject.

 

[augiedoggy]

I learned something today...
thanks for clearing things up.

 

[cfrazier77]

To the original question. I use a 22 gallon brewhemoth and I have never had a problem with my 5 gallon batches witch are the majority of what I brew. You will be fine.