oxygen permeability of plastic

[MachineShopBrewing]

I was able to get gas permeability information from the Ale Pail manufacturer.

This is the chart that they gave me:

GAS RATE(cc/mil/24hrs/100in^2)

CO2 345
Ethane 236
Hydrogen 321
Natural Gas 113
Oxygen 111
Freon 12 95
Helium 247
Nitrogen 53
Sulfur Dioxide 306

I have no idea how to relate cc/mil/24hrs/100in^2 into ppb or ppm, so I am hoping you chemistry guys can help me out there.

 

[Oldsock]

The numbers arrive and the thread dies?

To make those numbers usable you would have to determine the surface area of an ale pail. https://www.homebrewtalk.com/f11/ale-pail-dimensions-72525/ Let’s assume it is actually just a cylinder with a diameter of 11 inches and a height of 17.5. Which is 795 In^2. That means that we need to multiply the numbers supplied by 7.95, so 882 ml of oxygen every 24 hours… that doesn’t sound good. From there you would need to figure out how much oxygen that is compared to how much beer is in the fermentor.

As someone else said, the smaller the fermentor is the more oxygen it will let in because of the higher surface to volume ratio.

My bigger concern with buckets has always been the seal. If anyone hasn’t seen it Better Bottle did an oxygen permeability study on airlocks and bungs: http://www.better-bottle.com/pdf/Closures_Oxygen_Passage_Study.pdf

 

[dwoodfield3]

Supposing you would like to bulk condition your beer in a plastic food grade bucket with lid from the local HB store, could you not glue a layer of Mylar Space Blanket around bucket, lid, and bottom of bucket... that way even though the plastic container is not strictly oxygen impermeable, the oxygen will never touch the outsides of the container because of the space blanket. If space blankets can work as a barrier against hydrogen and helium, then by all rights it should stop oxygen too no? Or is the oxygen permeability of these buckets negligible anyway for long term beer conditioning? Just a thought....

Dom

 

[SmallBatchBrew]

However if we use a secondary, either bucket or carboy, we leave the CO2 protection and introduce air to the beer while racking. If we don't purge the secondary with CO2, then the beer is also in long-term contact with O2. The amount depends on the amount of headspace. In a 5 gallon carboy, it might not be much. In a bucket, it's going to be a very substantial surface area and a large enough volume of air.

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

 

[kingwood-kid]

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

I often add a tiny amount of table sugar (less than I use to carbonate) when racking to make this thin layer a little thicker. I can't tell you it works, but I'm pretty sure it does no harm.

 

[mduvigneaud]

My thinking in recently using buckets for primary fermentation, which allows me to produce batches just a hair under 7 gallons with the same gear as I use to make 5 gallon batches, is that the outward pressure of the denser CO2 should counteract the inward migration of oxygen. Maybe this wouldn't apply to a batch kept in a bucket for several months, or maybe I'm just wrong, but I'm chancing it for now.

But even then, the mere act of moving the beer will release some dissolved co2 left over from fermentation, so you're going to have at least a thin protective layer in the fermenter after racking. The O2 introduction happens more in the transfer process.

I guess I'm a little late in joining this thread, but I thought this might be useful...

Unfortunately, neither the pressure of the CO2 in the beer nor the thin layer of CO2 on top would keep O2 out. Any O2 in contact with the CO2 will diffuse into the CO2, and the CO2 will likewise diffuse into the O2 until they are completely, evenly mixed. This is, I believe, Henry's law relating to partial gas pressures.

As an example, the partial pressure of CO2 in normal air (the amount of CO2 contributes only a small fraction of a percent of the pressure because the amount of CO2 is so small) is significantly lower than the partial pressure of the CO2 from the beer (presumably close to 100 percent). On the flip side, the partial pressure from the O2 in the air (somewhere around 21 percent) is much higher than the partial pressure of the O2 from the beer (presumably close to 0 percent.) The result is that both gasses (CO2 and O2) will move from their areas of higher pressure to their areas of lower pressure.

This is exactly why a freshly opened beer (or soda) will eventually go flat and stale: most of the CO2 will escape out and O2 will get in and dissolve.

 

[evrose]

edit: nevermind

 

[Wynne-R]

Good job explaining partial pressure and equilibrium. Just don’t expect anyone to believe you. It’s sounds wacky that oxygen could be coming in while carbon dioxide is going out.

I’m not a chemist, but I did pass organic. Here’s the part I have trouble with; it’s the timing. Gordon Fix said the gases in the headspace would stratify before diffusing. So given sufficient volume of CO2 we should be pushing most of the O2 out the airlock. I wonder what sort of volume that would be. Is there enough in secondary?

Diffusion into the wort would be a lot slower, so going back to oldsock’s calculation, we should take the surface area of the bucket for the part above the wort and then multiply the rest by some tiny fudge factor.

Any chem engineers out there that can help us out?

 

[phoenixs4r]

A bit off topic, but curious if oxygen permeability is a moot point for folks who cold crash. I know a lot of folks do it and it always made me think that be the easiest way to introduce oxygen other than bad racking.

 

[weiht]

Now this thread is giving me 2nd thoughts about conditioning my RIS in a hdpe jerry can for 6 mths as I didnt want to hold up a keg for that amount of time.

I was planning to fill the beer into the jerry can and purge that small little headspace with CO2 and put it in the fridge for 6 mths.

hmmm

 

[Brewing_on_the_Internet]

Supposing you would like to bulk condition your beer in a plastic food grade bucket with lid from the local HB store, could you not glue a layer of Mylar Space Blanket around bucket, lid, and bottom of bucket... that way even though the plastic container is not strictly oxygen impermeable, the oxygen will never touch the outsides of the container because of the space blanket. If space blankets can work as a barrier against hydrogen and helium, then by all rights it should stop oxygen too no?

Does anyone have thoughts on this?

 

[eastoak]

Originally Posted by dwoodfield3 View Post
Supposing you would like to bulk condition your beer in a plastic food grade bucket with lid from the local HB store, could you not glue a layer of Mylar Space Blanket around bucket, lid, and bottom of bucket... that way even though the plastic container is not strictly oxygen impermeable, the oxygen will never touch the outsides of the container because of the space blanket. If space blankets can work as a barrier against hydrogen and helium, then by all rights it should stop oxygen too no?

Does anyone have thoughts on this?

yes, it's a solution looking for a problem.