Author: Marshall Schott
When I first started brewing at home, I started fermentation in a 6 gallon plastic bucket then transferred to a 5 gallon glass carboy a few days in for “secondary” fermentation. I realized a few years later that this secondary step was largely unnecessary and stuck with using buckets for quite awhile, swapping out the standard 6 gallon plastic pail for a few 8 gallon buckets with spigots. I began interacting with more homebrewers and realized many, if not most, were fermenting in large glass carboys, which I’d avoided out of fear of pain and love of limbs. I began researching the plethora of information and opinions (mostly opinions) regarding the differences between plastic buckets and glass carboys, my obvious purpose being to seek data that would confirm my decision to use buckets. Probably the most common argument against buckets is that they are more oxygen permeable than glass, while carboy haters spoke of the dangers of glass and often provided photographic proof. I sort of stopped caring.
Then one day it happened, I went to my fermentation chamber to prepare 2 buckets for kegging when I noticed the spigots on each were covered completely in mold. After a 15 minute tirade that included my non-beer-loving wife talking me out of ditching the hobby completely, I kegged the beers using an old siphon then threw the buckets in the recycle bin with plans to drop some cash on a few new carboys. While browsing the web that night, I was reminded of another option– PET carboys. Not only were they lighter and much less likely to sever a toe than glass, but they cost less and apparently were less oxygen permeable than buckets. Given my obsession with convenience, I threw the sterile siphon starter in my cart with 6 PET carboys, a few stoppers, and some airlocks. The next day, I sorrowfully removed the buckets from the recycle bin, washed them out real good, and figured I’d use them to measure out water and hold sanitizer solution.
It’s been a couple years since I started using these plastic carboys almost exclusively in my brewery and I have absolutely no regrets, but I began wondering again just what, if any, differences might be experienced in the same beer fermented in a bucket versus one of these PET fermentors.
| PURPOSE |
To evaluate the differences between 2 beers made from the same wort and pitched with the same yeast, the only variable being vessel of fermentation, with half fermented in a PET carboy and half fermented in a plastic bucket.
| METHOD |
I made 10 gallons of IPA (recipe similar to A Lil Slack IPA using a novel hop) next to another batch one early morning.
I selected one of my favorite ale yeasts, WLP090 San Diego Super Yeast, from my bank of harvested yeast and had the starters all ready to go by brew day.
Another typical brew day with all the wonderful sights and smells of this delicious hobby. One thing I really enjoy about first wort hopping is how aromatic the wort instantly becomes even before boil is reached.
Once the boil was complete, I transferred half of the wort into a PET carboy per my typical routine then, for the first time in years, racked the other half into a well cleaned and sanitized bucket (the one I haven’t used at all since the aforementioned fiasco).
Both fermentors were placed in my fermentation chamber, temp probe sandwiched between them, the wort was allowed to chill to my target pitching temp of 64°F, then the yeast was pitched. This is where I engaged my ale fermentation profile in The Black Box and let it do its thing. Both beers were active a day later.
I took an initial hydrometer reading 6 days later.
I was surprised to see the bucket beer with what appeared to be a specific gravity about .001 higher than the carboy beer. Would this come through in the final beer? What would cause this difference? I took another sample a couple days later and observed the same FG, it was time to keg these beers using my usual method.
I dropped the CO2 from 30 psi to 12 psi about 36 hours later, dumped the first 8 oz from each keg just to clear things up, then let them sit another 24 hours before taking a sample to taste. They definitely looked different at this point.
I start my siphon from the middle of the carboy, allowing me to avoid sucking up too much trub while kegging. With the bucket, the spigot is low enough that trub actually builds up in it and, despite my best efforts to clear it prior to packaging, quite a bit made it into the keg. The only real downside to this is that it took a few more throwaway ounces to get to the “clean” stuff, as the floaters were absent by the time the beers were ready for evaluation.
| RESULTS |
A total of 10 people participated in the tasting panel for this exBEERiment. Each taster was blindly presented with 3 beer samples and instructed to select the one that was different from the others. Each participant was served 2 samples of the beer fermented in the bucket and 1 sample of the beer fermented in the carboy. Those participants who accurately chose the beer that was different were then asked to complete a more detailed survey comparing just the 2 different beers. The tasting panel included homebrewers, Cicerone certified beer servers, and BJCP judges.
On the initial triangle test, 7 of the 10 participants (p=0.007) were able to correctly detect the different beer, a statistically significant rate that surprised the hell out of me. I later learned that probably the most qualified participant, a nationally ranked BJCP judge, was the only person to indicate the beers had “no detectable differences.”
Of the 7 tasting panel participants who completed the second survey, most agreed both beers were very similar in appearance with there being no overwhelming preference for either. While most concurred the beers were somewhat similar in terms of aroma, a surprising majority (5/7) selected the one fermented in a bucket as being more preferable, with one person commenting the carboy beer “smells slightly lighter.” What’s more is no one selected “no detectable differences,” suggesting fermentation vessel may have some impact on aromatics. Interestingly, the data on aroma is almost exactly swapped when it comes to flavor, as the majority seemed to prefer the taste of the beer fermented in the carboy. However, comments were somewhat confounding with 1 person describing the carboy beer as having “more malt flavor” and another stating it is “a lot hoppier.” In the end, 2 of the 7 participants believed there to be very little similarity in flavor between the beers, while the others said they were either somewhat similar (3/7) or exactly the same (2/7). Regarding mouthfeel, the majority thought they were at least somewhat similar with most (4/7) preferring the carboy fermented beer and only 1 participant indicating they perceived no detectable difference. Finally, when asked which beer was most preferred overall, 4 chose the beer fermented in the carboy, 2 chose the beer fermented in the bucket, and 1 did not choose due to there being no detectable differences.
At this point, the nature of the exBEERiment was revealed to the participants and they were asked a final question: which beer do you believe was fermented in the plastic carboy? Four of the participants, a small majority, incorrectly answered this question while 2 were accurate in their guess and only 1 said they were too similar to tell the difference.
My Impressions: In the numerous times I’ve tasted these beers, I’ve noticed they definitely aren’t exactly the same. At first, I was concerned maybe one of them picked up an infection, not because of off-flavors, but because my mind simply didn’t want to accept that they could possibly differ. After reviewing the results, I went back and tasted the beers again, clean palate and totally sober… yep, they’re different, if but just subtly. The bucket fermented beer seems to have a slightly richer flavor, whether from the malt or hops, I can’t be too sure. The carboy fermented beer seems somewhat cleaner to me, perhaps the .001 lower FG contributing to a crisper dryness, but I somehow doubt that’s all there is to it. Both beers are good and I’d be wary of selecting a fermentor based on these findings. For me, I’ll be sticking with PET carboys because I find them to be more convenient, plus no mold issues like I had with the buckets. Perhaps later I’ll borrow a glass carboy from a buddy and repeat this exBEERiment, as I know plenty of folks who still prefer it to either buckets or PET carboys.
| DISCUSSION |
I was always in the camp that believed the type of fermentation vessel one uses really doesn’t make a difference at all. In fact, I’ve made many of the same recipes in my old buckets as I have in my PET carboys and never noticed a big difference. These results were surprising to me in that it supports the notion that fermentation vessel may in fact impact the final character of the beer we make. Now, it doesn’t appear the differences are all that crazy or that either beer was necessarily significantly better/worse than the other, just that a panel of arguably qualified tasters were able to detect that something was different.
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29 thoughts on “exBEERiment | Fermentation Vessel: Plastic (PET) Carboy vs. Bucket In An American IPA”
Interesting. In the short time I have been brewing, I have often gone back and forth on wanting to move from buckets to either glass or PET carboy. The main reason I keep sticking with the buckets is that it seems the carboys would be more difficult to clean, especially when used as a primary.
Do you just soak your carboys in PBW or something? any scrubbing required to get the gunk off the sides?
Also, what do you have attached to the end of that hose to aerate that wort as you transfer?
cheers!
I soak my carboys in OxiClean Free for a few hours, usually overnight, and that has never failed me. There are gadgets out there intended to clean the inside of carboys, but I’ve never really needed one.
That’s a siphon spray wort aerator from MoreBeer, it’s a cheap and presumably effective little tool 🙂
I have the Plastic PET bottles, but I’ve thought about getting a big mouth bubbler. It’s a bigger top that would allow you to reach in and clean it easier.
+1 on the plastic big mouth bubblers. I picked up a couple of these and they have the best of both worlds. As an added bonus they are narrower than buckets or carboys so they fit better in chest freezers.
I have a pair of the glass ones as well, but would not recommend. The glass is cheap and they are fatter than a standard carboy.
While they seem like a decent in-between, I’ll be sticking with my PET carboys almost solely because I much prefer the sterile siphon starter to other types of siphons. Also, I’ve never had an issue cleaning them.
I’m just curious, why not siphon out of the bucket like you did with the carboy?
Because the bucket had a spigot, it’s the reason I went with it in the first place, I thought it’d be more convenient (it is compared to siphoning).
I purposefully use a bucket without a spigot for fermentation and then transfer to a bucket with a spigot for bottling because of all the gunk at the bottom. I thought that was what most people did. I guess one way around that would be to drill the hole yourself and make it high enough that the stuff at the bottom doesn’t get into it.
Oh, I don’t doubt what you do is likely the more popular method, I chose what I did as a first step, perhaps next time I’ll compare a glass carboy with a bucket setup more like yours. Cheers!
Was there a different amount of trub in the fermenters? I recall reading somewhere that a lack of trub can negatively impact fermentation to a degree.
I made an effort to transfer similar amounts of trub to each fermentor by giving the wort a good swirl to sort of homogenize things prior to transferring.
What’s your process for racking from the carboy? One thing I’ve always liked about racking from a bucket is that I can see what I’m doing. As I get to the bottom I tilt it a bit and move the tip of the racking can over to the edge. With a carboy I always either accidentally get a bunch of trub, or leave a lot of beer behind.
I’ve also used both glass and PET carboys. I still prefer the buckets because there’s no worry about blowoff, and cleanup seemed much easier to me. Also, hate to be nit-picky but those buckets are 8 gallon, not 6 :). The typical 6 gallon brew buckets come with regular bucket lids which are much more of a pain to get on and off (and would likely need a blowoff tube).
When I first bought my buckets I was planning on getting spigots, but luckily my LHBS owner talked me out of it. Thank you Kevin at MainBrew!
Great writeup! Interesting to note the slight differences. I wonder if it might be due to the increased headspace in the bucket.
I rack from carboy to keg using one of my favorite pieces of brewing gear, the sterile siphon starter. I usually remove the carboy from the cold ferm chamber 10-15 minutes prior to racking, placing a towel under one edge, then I start the sipon well above the yeast cake and slowly lower it so as to avoid any transferring of trub to the keg– I can see what I’m doing as well, usually from outside the carboy, but the red siphon tip is easy to see from the top as well.
I’m fully aware they’re 8 gallon buckets, the lids are even more difficult to get on/off than the typical 6 gal fermentation buckets I’ve used– I went with the larger buckets precisely to avoid blowoff.
If I use buckets, I’m using spigots… siphoning from a bucket is a PIA in my opinion (that’s all it is). I still hugely prefer PET carboys because, to me, they’re less cumbersome (easier to move) and I like that stealing a hydro sample doesn’t expose the entire top of my beer to O2, which may or may not matter.
Thanks, man, I appreciate the great feedback! Cheers!
Man I’ve really really enjoyed using my new Speidel fermenter. The spigot is extremely easy to clean and can be replaced with a cap instead pretty easy if you’ve swore off spigots completely. They are a bit pricey but the durable plastic, handels, crazy huge air lock and sizes make these worth it. Worth a look if you have some more dough to swing for fermenters.
I received a 15 gal Speidel for xmas last year, sold it within a couple months mainly because lifting 11 gallons of wort alone was making me feel like I was older than I am. It’s a great product, no doubt, but I’m quite happy with my PET carboys, I actually think they’re easier to move and I really like using my sterile siphon starter. Perhaps some smaller Speidels are in my future, we’ll see. Cheers!
Aren’t glass carboys odorless? Perhaps that made the difference
Glass doesn’t tend to hold onto odors, for sure, but this exBEERiment didn’t include any glass carboys… perhaps I’ll repeat it with glass in the future.
Oh yea, duh. But PET is supposed to have that trait too.
Haha. I haven’t noticed any leftover aroma’s in my PET carboys since I started using them a couple years ago, I usually soak them in an OxiClean solution for 12+ hours, perhaps that’s why. The buckets I use don’t really have leftover smells either.
Good job on this exBeeriment, this was a fun one to read about!
It would be interesting to see a comparison using a “control group” of sorts for each method; two samples fermented side by side in buckets compared to each other, and then compared to two samples fermented side by side in carboys, and then each compared as a group. My guess is that you may find nominal differences in two identical beers fermented in identical equipment, given that the best quality control and practices we can muster will still allow some impurities, imperfections, and variations. I’m trying to think of how i can possibly convince my wife that this is a scientific endeavor worthy of allocating more time/effort to brewing…
That’s way too sciency for me, man! Haha. As great is it would be to do that, my system (and motivation) sort of forces me to stick with more simple designs, though I believe the triangle test helps increase the validity. Maybe later, though…
I just the other night bottled a brew that was split into 2 buckets. Fermented in the same chamber as the same temp (although one was closer to the cooling source) that came out 4 points different (1.010 vs 1.014). I’m interested in how different they turn out to be.
I’m not overly surprised about your results – the surface area and headspace (and possibly level of air exchange) would be quite different for the two containers, leading to differences in ester and other O2-dependent flavours. I abandoned carboys for a loose-lidded bucket (sometimes replacing the lid with muslin) for more estery styles – I find this gives a bolder and more dynamic ester profile. The muslin “lid” can be overkill for an English beer, but makes for great hefeweizens & the more estery styles of Belgians.
I’d be curious to see how your experiment worked out for an estery-style of yeast. I’d bet you’ll see bigger differences.
Brulosopher, I am SOOOO glad I found your site. Your experiments are things that I have often worried and thought about, and you go the extra mile to actually run the experiment for me.
As far as the Big Mouth Bubbler (PET ones), DO NOT BUY THEM. I bought one and returned it thinking it was poorly manufactured because it was PAPER thin in some spots, but not others. SO the online store exchanged it for me. Well I got the new one and it was the same piece of poorly manufactured crap. So I drilled a hole in it, installed a spout, used it four or five times before it cracked where the spout is. Piece of junk that has a great design idea behind it.
You drilled a hole in a product and were upset when it cracked where you drilled a hole?
I have a Big Mouth Bubbler (5G) and a Better bottle (5G) and a few 3G better bottles and they all work just fine, after numerous beers in them. Not sure what 10 year+ longevity is, but for now it works just great!
If you want a port, don’t be cheap and get a ported better bottle.
Ive heard about differences in dynamics of vessel size and shape effecting yeast performance and character, which would seem to be anecdotal evidence of this…i could see a big difference between a 30bbl stainless conical and my lowly fermentation bucket, but didnt think the size/shape of carboy vs bucket would be that different. Then again, theres something about yorkshire squares that produce significantly different beer than stainless in the same brewery so hey….
All plastics out-gas (release odour) , that’s the new car smell when you hop in a new vehicle. If you pick up a new fermenter you can actually just smell it. they also absorb flavours, so if you brew different flavoured beers in the same fermenter it will have an impact. Wash out a plastic coke bottle (pet) using your standard method. Put the cap back on and give it a day, then take the lid off and see if you can still smell it. The effect is very small given the impact of other flavours going on in beer and I doubt you could even account for it unless you did a side by side like this. I would like to see a test with borderline results repeated with plastic cup then glasses on a seperate sitting. I think that just serving in a plastic cup would have an impact and make it harder to pick up other differences.