60L fermentor

[TheWiggman]

Thank you.
This still doesn't give weight to the theory that volume of head space will affect anything. In fact is supports that it doesn't. The partial pressure of O2 in the CO2 enviroment (0) of the headspace won't change based on its volume following a fermentation. It will be zero regardless. In fact you could nearly argue that more head space would be better with this theory. It'll take more time to reach the same proportions as air in the head space, hence less oxidation risk.

Do you have any references brewing-related?

 

[Pokey]

Some good quotes from sources.

"Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow. Gases dissolve, diffuse, and react according to their partial pressures, and not necessarily according to their [/size]concentrations in a gas mixture."[/size]

"[/size]The partial pressure of an [/size]ideal gas in a mixture is equal to the pressure it would exert if it occupied the same volume alone at the same temperature. This is because ideal gas molecules are so far apart that they don't interfere with each other at all. Actual real-world gases come very close to this ideal."[/size]

http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Partial_pressure.html[/size]

Interesting read but it doesn't seem to mention gas migrating to a higher pressure vessel

 

[Greg.L]

for a given pressure of oxygen, if you increase the volume you will increase the mass of oxygen. That oxygen is available to react with the beer and any micro-organisms on the surface of the beer. As the oxygen reacts and dissolves the partial pressure at the surface drops so oxygen moves towards the surface from the headspace, until all the oxygen is consumed. This drop in partial pressure will draw more oxygen into the fermenter.

Basically the bigger headspace means more oxygen will be drawn in because of the lowering of the partial pressure.

This science doesn't relate just to brewing, it is common for all gas systems. In terms of the desirability of small headspaces, there must be a lot of references but I really can't be arsed. It isn't my problem if people use large headspaces, I just thought I would present the science for your elucidation.

 

[Greg.L]

Interesting read but it doesn't seem to mention gas migrating to a higher pressure vessel

The point is that the pressure of oxygen inside is much lower than the pressure of oxygen outside the fermenter.

"Gases will always flow from a region of higher partial pressure to one of lower pressure; the larger this difference, the faster the flow"

 

[butisitart]

if you're worried about too much bad air near a good brew, you can always sanitize a couple of 4L capped plastic juice bottles or similar, and throw them in the fermenter. that'll cut down on the air space.

 

[TheWiggman]

But that's the point - it's been elucidated but the quoted science doesn't support your view that more head space increases the risk of oxygen spoiling the beer.
Yes the pressure of oxygen inside is lower (I wouldn't say much in absolute terms) than the pressure of oxygen outside the fermenter, but the pressure difference won't change with a larger head space volume. More oygen will be drawn in yes, but that's irrelevent - as the beer might consume it it will just get replaced like you say. REGARDLESS if the volume. I believe it's O2% in the head space of the fermenter that matters, which is what the surface of the beer will see. This won't change with larger head space.

This is a critical point if the basis for your advice is the space in the fermenter head.

I think the only time it matters is where the space is so great that not all the air will get displaced with CO2, or where a measurable percentage of air remains following a ferment. For home brewers not doing open ferments, this won't happen.

My assumptions also support the large quantities of brewers who have successfully done smaller brews in large vessels with success. Might not be raw science, but if you tally up the sample size on this forum of people who have done it then we're talking a serious sample size of brews. If that's not supporting evidence then I'm not here. Soooo many variables in brewing and I've not heard one person quote "I was getting oxidation and/or infection issues which stopped when I used a smaller fermenter".

If there's a specific brewing text that discusses head space and infection risk I'm all ears. Until I see it though I think OP is 99.99% safe doing a small batch in a large fermenter, as are all of us.

 

[Greg.L]

More oygen will be drawn in yes, but that's irrelevent - as the beer might consume it it will just get replaced like you say. REGARDLESS if the volume.

This is the point - that oxygen is not just being consumed by the beer, but by various aerobic microbes (germs). If you think it is irrelevant that more oxygen is being drawn in then I obviously can't convince you. You are obviously more convinced by all the people on this forum who reassure each other that a huge headspace is fine.

 

[Yob]

Dismiss as you may the Anecdotal evidence that suggests that it isnt a critical point that will destroy your beer.

Not for the first time, I would also like to see a paper discussing the subject. At a homebrew level.

 

[pcmfisher]

This oxygen, is it being drawn in though the plastic fermenter, the airlock, the rubber seal or only when using glad wrap?

 

[i-a-n]

I agree with Greg, headspace can be a risk.
I agree with Yob, gas will flow from a higher ambient pressure to a lower one.
My take.....use your 60 litre fermenters.... Then.... .. Don't piss about with it, when it's done fermenting get it bottled or kegged.
You'll be enjoying it sooner that way.

 

[TheWiggman]

This is the point - that oxygen is not just being consumed by the beer, but by various aerobic microbes (germs). If you think it is irrelevant that more oxygen is being drawn in then I obviously can't convince you. You are obviously more convinced by all the people on this forum who reassure each other that a huge headspace is fine.

More in the space does not equal more exposed to the beer. I'll make it simple with two scenerios -

100l of headspace, 2% oxygen by weight.
1l of headpace, 2% oxygen by weight.
Oxygen is replaced as it is consumed.

There's more oxygen in the larger headspace, but the environment still has 2% oxygen by weight. If the surface area of the beer is the same in both, why would one absorb any more oxygen than the other?
If there was a sealed lid on it, totally different story. But there isn't, there is an incredibly small ability for gas to transfer.

I'm not sure if you're deliberately misinterpreting what I said or you don't understand. If the proportion of oxygen exposed to the surface of the beer is stable the actual volume of oxygen in the headspace is completely irrelevent.
If I need to breathe, having billions of cubic metres of oxygen in the atmosphere doesn't make the way I breathe any different.
My statement is that oxygen will be consumed at the same rate with both scenerios, for the miniscule amount of oxygen that might make its way in. Nobody on this forum has needed to convince me, looking at the thoery and science in isolation has convinced me. Further reading to the contrary will convince me otherwise, which as I've said I'm still open to.

I seem to be repeating myself. I think I've said enough. Looking forward to a hoppy APA tonight in the snow, where I'll no doubt still be thinking about this trying to work out if the headspace really matters.

 

[Greg.L]

This oxygen, is it being drawn in though the plastic fermenter, the airlock, the rubber seal or only when using glad wrap?

Mainly through the seal and the walls of the plastic fermenter. The volume of headspace is significant partly because at the surface of the beer is where most infections take hold. The yeast cells in the beer act to mop up a fair bit of oxygen. Hop chemicals also have antibiotic powers. The surface of the liquid is where a lot of the action is. If there is a big headspace it is a perfect reservoir of o2 to replenish the needs of bacteria and film yeast. The more headspace, the more oxygen available, though things like acetobacter can work their magic in the liquid as well if there is any dissolved oxygen available. Permeability to oxygen ranges from very high for gladwrap, less for ldpe then hdpe only slowly, glass and S.Steel are pretty much impermeable, but a little bit of oxygen will always infiltrate unless you have a very good seal.

 

[AlwayzLoozeCount]

I've been wondering if I can fit a 60 litre fermenter in my ferment fridge for a while now. Can someone please measure the diameter of the bottom of their 60 litre fermenter.... For science.
Thanks in advance.

 

[AlwayzLoozeCount]

I've been wondering if I can fit a 60 litre fermenter in my ferment fridge for a while now. Can someone please measure the diameter of the bottom of their 60 litre fermenter.... For science.
Thanks in advance.

 

[Crouch]

I've a shiny new 50l stainless FV for single batch fermenting,

Greg beats this drum a bit without much supporting evidence, certainly not an issue in the norm.

If it was, the infection photo thread would be quite a bit longer

i was just reading through that BB thread today ... sad face for me, I missed it.

I've frequently put single batches into a 60l and never had a problem ... now, back to read the rest of the thread.

Thank you

 

[pcmfisher]

Greg.L, on 01 Aug 2014 - 4:35 PM, said:

Mainly through the seal and the walls of the plastic fermenter. The volume of headspace is significant partly because at the surface of the beer is where most infections take hold. The yeast cells in the beer act to mop up a fair bit of oxygen. Hop chemicals also have antibiotic powers. The surface of the liquid is where a lot of the action is. If there is a big headspace it is a perfect reservoir of o2 to replenish the needs of bacteria and film yeast. The more headspace, the more oxygen available, though things like acetobacter can work their magic in the liquid as well if there is any dissolved oxygen available. Permeability to oxygen ranges from very high for gladwrap, less for ldpe then hdpe only slowly, glass and S.Steel are pretty much impermeable, but a little bit of oxygen will always infiltrate unless you have a very good seal.

Can you tell me how much oxygen is going to permeate through my hdpe fermenter in 2 weeks, given that I have a good seal.( My airlock holds an uneven pressure whether it's positive or negative).
I know that a positive co2 pressure does not inhibit o2 but that is not the point.
I am also not concerned whether it is actual volume of o2 or percentage of o2 that is the issue, I want to know how much is going to get through, in say a half full 60L fermenter.

I propose it is 1/4 of 3/8 of 5/16 of **** all. And whatever does get through makes 0.0% difference.
If you have to go to more than one decimal place I am not interested.

 

[Bribie G]

If oxygen permeates through the walls of plastic containers then the makers of fresh wort kits are a mob of thieving charlatans.

 

[Grott]

So does this now mean that everyone that uses the new Coopers style fermenters with the sliding collar insert that you remove during the process have a crook brew for allowing oxygen in during the removal process? In other words Coopers are advising to introduce oxygen to the brew- don't think so.

 

[Greg.L]

There is this thing called google, if you search oxygen permeability of hdpe plastic you might get some results. Most fermenters are hdpe.
One site gives a figure for hdpe of 4000 cm3-mil/m2/day but I am not sure what the thickness is. The thicker the wall of the fermenter the less permeable it is but if you use ldpe it is quite permeable.

As I said the wort itself is more resistant to oxygen but the headspace has a big impact. Oxygen will also get past an o-ring but very slowly, an o-ring is a hell of a lot better than gladwrap and a rubber band.

 

[MastersBrewery]

There is this thing called google, if you search oxygen permeability of hdpe plastic you might get some results. Most fermenters are hdpe.
One site gives a figure for hdpe of 4000 cm3-mil/m2/day but I am not sure what the thickness is. The thicker the wall of the fermenter the less permeable it is but if you use ldpe it is quite permeable.

As I said the wort itself is more resistant to oxygen but the headspace has a big impact. Oxygen will also get past an o-ring but very slowly, an o-ring is a hell of a lot better than gladwrap and a rubber band.

so basically it's crap beer unless it's fermented in glass or ss. Hmmm interesting, of all those award winners is comps over the years and I'd say more than 90% were using plastic. And if your so sure of the permeability of the glad wrap lid why not test in out and glad wrap yer self in a big plastic container, by your theory you'd be fine!

MB