Airlocks- why?

[Matt in Birdham]

Why not use one they are as good as a tea towel or foam bung plus you can see how much its fermenting

Exactly - that's my take on it too. It's just as easy as any other method, really, with the added benefits (or, at the very least - not drawbacks) of reducing possibility of contamination, retaining CO2 and providing a nice bit of visual feedback on the state of the fermentation. So really, the question should be "why not use an airlock?". One answer I suppose could be when you are height restricted.

When I was brewing down-under there was a bit of a fad for using cling-flim and a big elastic band, the reasons for which were always unclear to me.

[Jocky]

I've always used one because that's what I was told to do when I started brewing kits. I'm going to try without one in my next brew, as I'll be doing a saison using WLP565, and this is meant to be pressure sensitive.

I'm using WLP565 right now, and I've only ever used it with an open ferment and certainly have had no problems, but equally I've not used an airlock on it either.

I start at 22C and ramp up to 30C by the end of ferment (and then I close the fermenter up!). The resulting saison is really nice, but it's entirely a showcase for the yeast - pilsner malt, some flaked wheat, sugar, noble hops late in the boil.

If I wasn't making a saison specifically to show off that yeast flavour (e.g. a dark saison, more malty) I'd probably plump for one of the more robust saison yeasts.

Go and check out the yeast forum for some threads on WLP565.

[Matt in Birdham]

The 'CO2 blanket' is a dangerous simplification. Once mixed, gases don't unmix under a normal gravitational force, it's too weak a force to overcome entropy that causes gases to mix.

It would be better to think that you have a higher concentration of CO2 (and/or a lower concentration of O2) in the headspace that helps slow the staling/oxidative reactions.

Your pressure barrel works well because the carbonation process in the keg is fermentation that reduces the O2 and increases the CO2 in the headspace.

Agreed - I think they have shown that any sort of disturbance (lid removal) will mix gases in the headspace very rapidly. I have taken to using much shorter cold crashes in primary these days (a couple of days only, which still drops the bulk of the yeast). I then get the beer into a keg asap and get it purged. Even with an airlock (when you can assume that pretty much the entire headspace is CO2 at the end of fermentation) the beer will start to absorb that CO2 as it cools and pull in air through the bubbler. I've had a few oxidised beers (mostly when bottling) and I do everything I can to prevent it now.

[Clibit]

Some yeasts prefer a non-sealed fermentation. Saison yeasts like Du Pont spring to mind, but I'm wondering how much effect the open/closed choice has on different yeasts.

[Jocky]

The 'CO2 blanket' is a dangerous simplification. Once mixed, gases don't unmix under a normal gravitational force, it's too weak a force to overcome entropy that causes gases to mix.

It would be better to think that you have a higher concentration of CO2 (and/or a lower concentration of O2) in the headspace that helps slow the staling/oxidative reactions.

Your pressure barrel works well because the carbonation process in the keg is fermentation that reduces the O2 and increases the CO2 in the headspace.

Agreed - I think they have shown that any sort of disturbance (lid removal) will mix gases in the headspace very rapidly. I have taken to using much shorter cold crashes in primary these days (a couple of days only, which still drops the bulk of the yeast). I then get the beer into a keg asap and get it purged. Even with an airlock (when you can assume that pretty much the entire headspace is CO2 at the end of fermentation) the beer will start to absorb that CO2 as it cools and pull in air through the bubbler. I've had a few oxidised beers (mostly when bottling) and I do everything I can to prevent it now.

I've gone a stage further and have a fermenter that can seal up properly air tight and I have installed an S30 valve so I can pressurise it before cold crashing.

[Matt in Birdham]

I've gone a stage further and have a fermenter that can seal up properly air tight and I have installed an S30 valve so I can pressurise it before cold crashing.

I've wondered about doing something like this. I think someone might have mentioned this on here before, but has anyone tried essentially filling a bag (or a balloon) from an outlet in the FV, so that the CO2 can be pulled back into the vessel during cold crash? I would envisage attaching said bag a couple of days into the ferment, when the headspace should have purged just about all the air and be mostly CO2. More CO2 would outgas into the gas bladder and could be pulled back in during cold crash.
Is that a completely ridiculous idea? I wonder how hard it would be to implement.

If memory serves, they do retain CO2 produced during fermentation in Germany so that they can add it back (forced) to carbonate, to comply with the purity laws.

[Jocky]

I thought about doing that, but frankly I couldn't figure out how to secure the balloon, and I thought it would take a lot of pressure to blow up the balloon.

Whereas I knew I could get an airtight fermenter (or just and old pressure keg) and stick CO2 into it via an S30.

[Matt in Birdham]

Yeah. I think something more like a bag, that didn't take much pressure to inflate. I think it could be troublesome though - what would happen if it overinflated? I have no idea what sort of gas volumes we are dealing with in an active ferment - could be quite a lot I guess. Might be fun to try it one day.

[IPA]

Foam bungs are best if your FV is suitable.

I haven't seen these, I'll have a search as this would be a better method than using a tea towel! Cheers

Here they are.
http://www.northernbrewer.com/brewing/b ... pers-bungs

http://www.northernbrewer.com/brewing/b ... er-46-60mm

They are available in England as well.

[Andy]

I use one because I ferment in a converted fridge and IMO fridges are bug havens.

[Jocky]

Foam bungs are best if your FV is suitable.

I haven't seen these, I'll have a search as this would be a better method than using a tea towel! Cheers

Here they are.
http://www.northernbrewer.com/brewing/b ... pers-bungs

http://www.northernbrewer.com/brewing/b ... er-46-60mm

They are available in England as well.

From king scientific: http://www.kingscientific.co.uk/lab-equ ... am-stopper

Or plenty of places on ebay.

[Hogarth]

Yeah. I think something more like a bag, that didn't take much pressure to inflate. I think it could be troublesome though - what would happen if it overinflated? I have no idea what sort of gas volumes we are dealing with in an active ferment - could be quite a lot I guess. Might be fun to try it one day.

I once inflated a black bin bag with CO2 from the fermenter, and that (IIRC) was maybe a day's worth.

I think the idea of having a CO2 reservoir for when you cold-crash or take hydrometer samples at the end of fermentation is a good one. How about one of those silvery wine-box bags, attached to the exit of airlock?

I haven't tried it yet. But after getting a couple of oxidised beers, which I attribute to pulling oxygen in while filling my hydrometer jar, I always airlock, and I'm very, very careful about taking late readings. The 'blanket of CO2' idea is fine as long as your beer is still producing CO2 and there's nothing disturbing the gases in the headspace. But sooner or later the the gases are going to mix.

[Matt in Birdham]

How about those accordion style bottles? Something like this.
Imagine a plastic bucket type fermentor, with the top foot or so made in an accordion style. You could ferment for a couple of days through an airlock, then seal it up and let it expand, then crash cool and contract. It could be a nightmare to clean though!

Even better - here is a 15L accordion Jerry can!

[MarkA]

Here they are.
http://www.northernbrewer.com/brewing/b ... pers-bungs

http://www.northernbrewer.com/brewing/b ... er-46-60mm

From king scientific: http://www.kingscientific.co.uk/lab-equ ... am-stopper

Or plenty of places on ebay.

Thanks! Got some on order so will give them a try

[Jocky]

How about those accordion style bottles? Something like this.
Imagine a plastic bucket type fermentor, with the top foot or so made in an accordion style. You could ferment for a couple of days through an airlock, then seal it up and let it expand, then crash cool and contract. It could be a nightmare to clean though!

Even better - here is a 15L accordion Jerry can!

The problem is taking samples. The moment you open up the fermenter to check something, or add dry hops, or whatever else then your CO2 balloon will rapidly empty itself.

All in all, keeping an air tight fermenter well buttoned up post ferment should be enough to avoid the majority of oxidation.