Extended Fermentation in Plastic vs. Glass

In the “To Secondary, or NOT to Secondary” thread, many said they were fermenting and conditioning their beers in the Primary for extended periods.

So…the question… Is there any issue with using a plastic bucket as the Primary/conditioning vessel, or should it be glass??? I know some say they FEAR oxygen contamination in plastic, but how much of a REAL issue is it?

Thanks

When you say “extended period”, how long are you talking about after the end of fermentation? During fermentation, there is no worries about oxygen because the yeast will scavenge it and produce CO2 to protect the beer. And as long as you don’t then disturb the resultant volume of CO2 in the bucket headspace, it will take a very long time (many months at least) before enough oxygen permeates through the plastic to have any affect on a full batch of beer.

I’ll routinely ferment in plastic buckets and then rack directly to a keg about a month later. No problems at all with that. The longest primary I’ve done in a bucket is about 18 months. But that was a lambic and some of the sour bugs need a bit of oxygen so they can do their thing, which makes plastic the next best thing to a wooden barrel for that purpose.

Very real Chris. I am a very lazy brewer and had many batches get oxidized in plastic. Many many gallons of cider turned to vinegar. I support glass now.

Very much agree with Dave on this one. As soon as primary fermentation is over and CO2 is not being driven out of solution, the risk of oxygen contamination is very real. The problem isn’t the plastic, though.

There are a few things going on here. The CO2 blanket protects the beer in the short term, but oxygen will diffuse into it and you’ll eventually have the same concentration inside the bucket as in the atmosphere around it. The main culprits are lids, which are notoriously leaky, and the airlock itself. Better Bottle did some really nice studies on oxygen permeability with various airlocks, but the water in the airlock by itself will allow oxygen to diffuse into a carboy. Also, the design of a bucket requires a large amount of headspace, so that’s potentially lots of oxygen getting into contact with your beer.

Plastic carboys are great, but the way to make them work the best is to top off either a glass or plastic carboy to minimize the headspace and limit the total oxygen allowed to come into contact with the beer. Even with a sour, you won’t see many pellicles forming with a topped-off carboy.

One caveat - By “extended fermentation,” I’m thinking months, not weeks. For weeks, you’ll usually be fine with a bucket.

+1. I do agree that plastic is fine for short ferments / short time. Not that I’ll do it myself anymore, as I can never trust myself enough not to be lazy!

This is a very timely post. I brewed NB’s Barley Wine in January. After about three weeks I transferred from a plastic bucket primary into a plastic 6 gallon carboy to continue aging (it went from 1.090 to ~1.020).

When I transferred, I racked onto one pound of dark brown sugar dissolved and boiled in about a quart or so of water. There’s maybe a half gallon of head space in the carboy (definitely less than one gallon). It bubbled pretty well for a week or so and now, after almost a month in secondary, it still bubbles every couple of minutes so I’m hopeful the CO2 coming out of solution is enough to keep the blanket from getting too much oxygen.

The recipe calls for aging in secondary for 4-5 months, but I’m not sure that is a good idea in a plastic carboy so I’m thinking I may bottle it after about six weeks from the transfer date (about 9 weeks from the brew date) and use oxygen absorbing caps. Before bottling, I will take a couple of gravity readings a few days apart to ensure it is done.

Does this seem like a happy medium between bulk aging for the amount of time called for and reducing the risk of oxidation?

Sounds good to me! You could also steal a play from a winemaker’s book and top it up with some beer from another batch - I doubt that 1/2 gallon mixed in 5.5 gallons of barley wine would be noticeable. I’ve been making more and more sours lately, and have started overshooting the recipe by about a gallon to make sure I have enough left after primary to competely fill a 5-gallon carboy. Annoying that those things actually hold 5.5 gallons, and 3-gallon carboys require 3.5 gallons to fill properly. The little bit left, if there is any, can go in a growler or quart bottle with airlock and some dregs tossed in, so nothing has to get wasted.

I’ve gone 6 weeks in plastic primary with no problems at all. After that I rack to kegs for conditioning.

Good timing on this. I just brewed my first BIAB, a witbier, and am fermenting in plastic, because my glass carboys are being used for other brews. I will check gravity to ensure that fermentation is complete, but should I transfer to keg after one, two or three weeks. What are the pros/cons of earlier or later transfer.

I guess I should have been more specific with my timeframe… I’m looking at holding in the plastic primary between 4 and 8 weeks.z

Given our other discussion regarding not racking to a Secondary, I see no need to crack open the primaries - at all, for any reason - until I’m ready to bottle (still don’t have kegs yet). At that time, I’ll check my F.G., bottle, and finish conditioning/carbing.

If the buckets remain undisturbed, I guess I don’t see how there would be much - if any - O2 transfer into the bucket; the positive pressure within the head space should remain until disturbed, yes?

That’s pretty much my standard procedure too. Just leave it long enough that I’m sure it is done and cleared.

My thinking too, though porkchop’s post above brings up diffusion of O2 through the air lock, which I hadn’t considered. So maybe for very long aging it might be best to replace the airlock with a solid plug after you are sure the fermentation is done. But I wouldn’t worry about it for a 6-8 weeks rest.

I could be wrong, but I don’t think you can count on positive pressure in a bucket over that long of a period. If I have time later I’ll post a link to the BB study, it really is an eye opener. It comes up easily in a web search, though.

6 to 8 weeks in a bucket? I agree with rebuilt, probably not a problem. If you have a sanitation problem, it’ll probably show up in that timeframe, though. I usually want my primary buckets back sooner than that anyways, which is a perfect excuse to rack it to secondary! :cheers:

4-8 weeks you should be fine in a bucket.

[quote=“Chris Roe”]I guess I should have been more specific with my timeframe… I’m looking at holding in the plastic primary between 4 and 8 weeks.z

Given our other discussion regarding not racking to a Secondary, I see no need to crack open the primaries - at all, for any reason - until I’m ready to bottle (still don’t have kegs yet). At that time, I’ll check my F.G., bottle, and finish conditioning/carbing.

If the buckets remain undisturbed, I guess I don’t see how there would be much - if any - O2 transfer into the bucket; the positive pressure within the head space should remain until disturbed, yes?[/quote]

4-8 weeks should be no problem, although I wouldn’t go over that.

Excellent!!! Thanks everybody! …I am limited on the number of fermenters I have, so as I move forward getting more, I’ll start looking at “better” ones.

I’d love to jump to kegs soon…but…we’ll see…

[quote=“Chris Roe”]Excellent!!! Thanks everybody! …I am limited on the number of fermenters I have, so as I move forward getting more, I’ll start looking at “better” ones.

I’d love to jump to kegs soon…but…we’ll see…[/quote]
Kegs are the perfect vessels for long-term bulk storage.

I ferment 100% of the time in buckets, since they are so easy to clean and sanitize, don’t break like glass carboys, are typically bigger volume than a carboy (providing more headspace), and are lightweight. Denny has been a great advocate of those benefits for years.

I rarely see the need to ferment a beer in primary more than 4 weeks – maybe an occasional pilsner, RIS, barleywine or Belgian, or with added late / “secondary” ferment addition of hops or fruit, or other BIG beer. I always dryhop in the keg after racking from primary.

I generally try to avoid opening the primary bucket later than 2 weeks into the ferment until time to rack, but if concerned such as when using a yeast prone to stalling, after getting in there to check the beer I sometimes add a gas blanket of co2 and then reseal the lid until it’s time to rack. Your biggest enemy is displacing the gas blanket with air late in the ferment after off-gassing is pretty much done, leading to staling. A little air very early in the ferment is no problem since it’s soon displaced by off-gassed co2, and within the first 60 hrs or so a little extra exposure to air is typically actually a benefit to the ferment.

Still, I miss watching the ferment that is only possible with carboys or similar clear vessels.

Brewsumore - you and I think alike. I haven’t touched the ones I still have in buckets, but if I had to, I was going to top off the headspace with CO2… Glad to know it works.

Dave- if you had cider turn to vinegar, wouldn’t that be an indication of acetobacter contamination, rather than oxidation? Just curious.

Kind of the same thing. Oxygen plus alcohol in presence of acetobacter = vinegar.