oxygen permeability of plastic fermenter

so i've read over time it will happen. my primary is a bottling bucket. what is my maximum time i have in it before i have to worry? and yes i am going to glass after this batch.

oh thanks to all for the great info.

A month is safe. But why would you keep it in the fermenter that long? Plastic is fine for fermenting. Glass is much more trouble then it's worth.

jimmythefoot said:

so i've read over time it will happen. my primary is a bottling bucket. what is my maximum time i have in it before i have to worry? and yes i am going to glass after this batch.

oh thanks to all for the great info.

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I've left beer in primary for 5.5 months with no issues. That whole "Oxygen permeability" of bucket argument has been pretty much disproven , for the time we're talking about anyway, so it should not be a caveat and taken off the table.

The amount has been proven to be as negligable as any other container, and more than likely was propaganda by the glass industry. The same argument HAS been made about better bottles as well, and few of us believe that either.

And it's been handed down as "fact" just like autolysis, hsa and other boogeymen to brewers.

You have to remember that there is co2 blanketing your beer and pushing out. So if there's co2 pushing out, there's nothing getting in.


Though as evidence has bore out over and over, including in this thread, the oxygen permeability issue, just like autolysis, is overrated.

The whole glass vs plastic issue is really a non issue anymore......You can use whatever you want..

maida7 said:

A month is safe. But why would you keep it in the fermenter that long? Plastic is fine for fermenting. Glass is much more trouble then it's worth.

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???? Have you missed the entire Long primary/no secondary discussions of the last five years? There's plenty of reasons to leave a beer a month or more in primary these days.....

But I agree that glass is more trouble than it's worth..

Revvy said:

???? Have you missed the entire Long primary/no secondary discussions of the last five years? There's plenty of reasons to leave a beer a month or more in primary these days.....

But I agree that glass is more trouble than it's worth..

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Yeah, I agree with a long primary and no secondary. But how long is long? Once fermentation has ended I see no advantage to keeping beer in the fermenter. 3 weeks is a long primary for me. IMHO, over a month serves no purpose. Most of my ferments (ales) are done fermenting in 3-7 days. I usually give them an extra week for the yeast to drop and then I move them to the keg.

Back to the OP: If your considering aging in glass, think about stainless. Kegs are cheaper and more durable then glass fermenters. Also, stainless is not permeable to light or oxygen. Even if you don't have a kegging system to serve beer from a keg, you could use them for bulk aging just like you'd use a secondary fermenter, except better.

Raj Apte has the best info on oxygen permeability of various substances.

http://www2.parc.com/emdl/members/apte/flemishredale.shtml

This info is reprinted in several books.

As for how much oxygen ingress into the beer I say less is best (you'll always get enough in the package for the beer to oxidize to pleasant levels over time), obviously there is a point of diminishing returns in terms of effort to keep oxygen out of the product. Your tolerance for oxidized beer, your storage conditions, and how long you like to keep beer are all factors affecting how much effort you should put into preventing oxygen ingress.

In other words, if you like the beer you are doing enough.

The notion that CO2 can keep oxygen out of anywhere is invalid. Gases move according to individual concentration gradients. CO2 presence has no bearing on O2 ingress.

ForgeHill said:

The notion that CO2 can keep oxygen out of anywhere is invalid. Gases move according to individual concentration gradients. CO2 presence has no bearing on O2 ingress.

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Doesn't positive pressure keep all gases out despite individual gradients? I suppose there's an equation for that.

No it does not. Imagine two gas bubble passing in a tube. Do you think they will repel each other, or simply phase through each other? Their being gaseous, they have no way of affecting each other. Individual gradients trump positive pressure. Think of a balloon expelling air, just because it is producing positive pressure doesn't mean gas molecules can't get it, because they can and do. Btw, the equation that dictates this phenomenon is Dalton's Law of partial pressures, which states that with a mixture of gases, their individual equilibria are dictated by their individual partial pressures.

maida7 said:

Yeah, I agree with a long primary and no secondary. But how long is long? Once fermentation has ended I see no advantage to keeping beer in the fermenter. 3 weeks is a long primary for me. IMHO, over a month serves no purpose. Most of my ferments (ales) are done fermenting in 3-7 days. I usually give them an extra week for the yeast to drop and then I move them to the keg.

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I often bulk age high gravity beers for 1-2 months in the fermenter. It takes considerably longer for a 9% beer to condition than a 5% beer. By bulk aging I get better uniformity in flavor across bottles.

Plastic buckets are O2 permeable but not at the level that should result in vinegar over the course of months. If you were fermenting in a bucket for years you might have more of an issue...

ReverseApacheMaster said:

Plastic buckets are O2 permeable but not at the level that should result in vinegar over the course of months. If you were fermenting in a bucket for years you might have more of an issue...

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Actually it will result in vinegar in a few months if acetobacter is present (hopefully it isn't). A couple of months is exactly how long it takes to get a good amount of acetic acid in a flanders beer if you ferment in a bucket.

The bigger concern is oxidation, which some beer consumers are very tolerant of. If you are wanting to produce a beer with minimal oxidation, the permeability of HDPE is profoundly higher than glass (although it is hard to get zero oxygen ingress in a carboy, as the available closure methods have much higher permeability than the glass, still you can easily be at a hundredth or less of the gross permeability of a bucket).