Purged headspace of secondary with co2. Does this work?

[HObrew]

Hi all,
Yesterday I racked yooper’s oatmeal stout into a glass carboy and found the headspace to be excessive.

I took a gas hose and filled the headspace with co2. Just for fun, I took a sample of the gas inside the headspace with a straw and confirmed it was largely co2 (not a genius idea.. I know).

Does anyone see any reason why this won’t work? I have heard of people putting glass marbles to take up space but wasn’t too keen on that idea.

 

[radwizard]

I purge secondaries with co2 if there is not going to additional co2 produced. Works well for me. I purge - rack - purge head space - then bung it. I do my best to plan for minimal head space as well, but this doesnt always work out.

 

[RM-MN]

i think you have a good plan. Most bacteria cannot survive in beer because of the alcohol and acidity. The few that can need oxygen and by filling that space with CO2 you have eliminated that avenue for contamination too. There may be one or 2 bacteria that can survive all 3 factors so you still need good sanitation practices.

 

[Premnasbiaculeatus]

It is a good idea, and very effective.

 

[flars]

Filling the head space with CO2 will work most of the time. You would need to cap the carboy with a solid stopper. An air lock will allow the molecules of the atmospheric gases to equalize in the head space of the carboy.

Any continuing fermentation in the carboy will produce more CO2 increasing the pressure. The solid stopper may blow off.

An increase in temperature may cause enough internal pressure to develop to blow the stopper off.

A sharp decrease in atmospheric pressure may raise the internal pressure causing the stopper to blow off.

Using CO2 when there is excessive head space is a worth while method to try for preventing oxidation. When no severe adverse conditions exist we have success. Best we can do as home brewers is to try alternative methods to produce good beer.

 

[MrHopScotch]

Filling the head space with CO2 will work most of the time. You would need to cap the carboy with a solid stopper. An air lock will allow the molecules of the atmospheric gases to equalize in the head space of the carboy.



Any continuing fermentation in the carboy will produce more CO2 increasing the pressure. The solid stopper may blow off.



An increase in temperature may cause enough internal pressure to develop to blow the stopper off.



A sharp decrease in atmospheric pressure may raise the internal pressure causing the stopper to blow off.



Using CO2 when there is excessive head space is a worth while method to try for preventing oxidation. When no severe adverse conditions exist we have success. Best we can do as home brewers is to try alternative methods to produce good beer.

I'm not so sure about this. An airlock does allow exchange of gases in or out *if* there is a pressure differential between the atmosphere and the carboy. Unless the pressure drops significantly in the carboy, no atmospheric gases will be moving into the headspace. No bubbling means no gas exchange either direction.

That said, reducing the temperature (and therefore the pressure) of the carboy will cause some atmospheric gases to enter through the airlock. If you plan on cold crashing in the fermenter, this is something to consider.

 

[doug293cz]

I'm not so sure about this. An airlock does allow exchange of gases in or out *if* there is a pressure differential between the atmosphere and the carboy. Unless the pressure drops significantly in the carboy, no atmospheric gases will be moving into the headspace. No bubbling means no gas exchange either direction.

That said, reducing the temperature (and therefore the pressure) of the carboy will cause some atmospheric gases to enter through the airlock. If you plan on cold crashing in the fermenter, this is something to consider.

Actually, a water filled airlock will not prevent O2 entry into the vessel even if the pressures are equal inside and outside the vessel (i.e. no bubbling.) O2 diffuses readily thru water, and because of the difference in O2 partial pressure in the atmosphere, and inside the vessel, there will be a net movement of O2 into the vessel.

Brew on

 

[MrHopScotch]

Actually, a water filled airlock will not prevent O2 entry into the vessel even if the pressures are equal inside and outside the vessel (i.e. no bubbling.) O2 diffuses readily thru water, and because of the difference in O2 partial pressure in the atmosphere, and inside the vessel, there will be a net movement of O2 into the vessel. An "S" type airlock is better than a three piece airlock because the diffusion distance is longer.



Brew on

Alright, I agree that there is nonzero o2 diffusion through the airlock liquid. That said, I'm willing to guess that the rate is very low. Furthermore, I suspect that there will be a lot more o2 in the headspace as a result of imperfect purging than will diffuse in through the airlock in the time the beer is in secondary.

If you have evidence to the contrary, I'm all ears. But I think it might be a little extreme to suggest that the OP must use a solid stopper given the potential for additional issues if there is pressure change, more fermentation, etc.

OP: purging the headspace was a good call, and should make a pretty positive impact on your beer. Cheers!

P.S.
Is there a reason you are using a secondary for this beer? Most people these days advocate for eliminating the secondary entirely unless you are doing some long term aging. But there are a million threads on that, and we don't need to beat the dead horse here unless you want to... [emoji6]

 

[doug293cz]

Alright, I agree that there is nonzero o2 diffusion through the airlock liquid. That said, I'm willing to guess that the rate is very low. Furthermore, I suspect that there will be a lot more o2 in the headspace as a result of imperfect purging than will diffuse in through the airlock in the time the beer is in secondary.

If you have evidence to the contrary, I'm all ears. But I think it might be a little extreme to suggest that the OP must use a solid stopper given the potential for additional issues if there is pressure change, more fermentation, etc.

...

Here is a study of O2 ingress for various carboy closures. The two common airlock designs are covered. I did incorrectly remember the results for "S" vs. three piece airlocks, so I will edit my previous post.

Depending on your equipment and CO2 purge process, you can be anywhere from single digit ppb O2 up to many thousands of ppm. So, the significance of diffusion back thru the airlock can be very different depending on where you are in the spectrum.

Brew on

 

[MrHopScotch]

Here is a study of O2 ingress for various carboy closures. The two common airlock designs are covered. I did incorrectly remember the results for "S" vs. three piece airlocks, so I will edit my previous post.



Depending on your equipment and CO2 purge process, you can be anywhere from single digit ppb O2 up to many thousands of ppm. So, the significance of diffusion back thru the airlock can be very different depending on where you are in the spectrum.



Brew on

Interesting read, thanks!

 

[brick_haus]

Here is a study of O2 ingress for various carboy closures. The two common airlock designs are covered. I did incorrectly remember the results for "S" vs. three piece airlocks, so I will edit my previous post.



Depending on your equipment and CO2 purge process, you can be anywhere from single digit ppb O2 up to many thousands of ppm. So, the significance of diffusion back thru the airlock can be very different depending on where you are in the spectrum.



Brew on

Wow, good info. Now I need to make a stainless blow off tube for my conicals to replace the silicone tubing that I have been using!