A mason jar makes about a pint of sauerkraut. A cabbage makes about two quarts. That arithmetic is why almost everyone who keeps fermenting eventually buys a crock — you get tired of splitting one cabbage across four jars and juggling four sets of weights.
The other reason is the water seal. A traditional fermentation crock has a moat around the rim; the lid sits down into it and the water forms a physical barrier that lets carbon dioxide bubble out and lets absolutely nothing back in. No burping, no valve to fail, no oxygen. It is a two-hundred-year-old design that solves the problem more elegantly than anything sold since.
Crocks are heavier, more expensive and less convenient than jars, and they are genuinely better at large batches. Below are seven worth buying, and an honest guide to what size you will actually use. If you are still deciding whether fermenting is for you, start with our mason jar fermentation kit guide instead.
Our Top 7 Picks for the Best Fermentation Crock
Best Overall: TOMO Fermentation Crock with Weights
The TOMO covers the fundamentals well and includes the weight stones, which is not a given — buying a crock and then discovering the stones cost another third of the price again is a common irritation.
The important features are the water channel around the rim and the fit of the lid into it. A well-made crock has an even channel that holds water without evaporating dry in a few days, and a lid that seats deeply enough to stay sealed. Both are right here.
The weight stones are the other half. They come as two half-moons rather than a single disc, which is what you want: two pieces fit through the opening easily, sit flat across the vegetables, and are far easier to lift out of a full crock than one heavy round slab.
Key Specifications
- Ceramic fermentation crock with water-seal rim
- Two half-moon weight stones included
- Lid seats into the water channel
- For sauerkraut, kimchi and pickled vegetables
Pros
- Weight stones included rather than sold separately
- Even water channel that holds its level
- Half-moon stones are easy to fit and remove
- Solid ceramic that blocks light
Cons
- Heavy, especially full
- Water channel needs topping up every week or two
- Ceramic chips if knocked
Best Value: SEEUTEK Fermentation Crock Jar, 1.3 Gallon (5 Litre)
Five litres is the size most home fermenters settle on, and this is the affordable version of it. It takes two or three cabbages comfortably, which is a realistic weekend batch, and it is still light enough to move when full without needing help.
The finish is less refined than pricier crocks — glaze thickness varies, and the lid fit can be slightly loose — but the mechanism is the same water seal, and the mechanism is what matters. Check the glaze inside for chips or crazing when it arrives, since damaged glaze on any low-fired pottery is worth avoiding for food use.
Key Specifications
- 1.3 gallon / 5 litre stoneware crock
- Water-seal channel design
- Includes weight stones
- Takes two to three cabbages
Pros
- The practical everyday size at a low price
- Same water-seal principle as pricier crocks
- Manageable weight when full
- Stones included
Cons
- Glaze and finish quality vary between units
- Lid fit can be looser than premium crocks
- Inspect for chips or crazing on arrival
Best Large: 7-Litre Fermentation Crock with Weights, Porcelain Water Seal
Seven litres is a serious crock — four or five cabbages, or a genuinely large batch of pickles — and it is the right size if you have a garden producing more than you can eat, or if you ferment for a household rather than for yourself.
Porcelain rather than ordinary stoneware is the notable feature. Porcelain is fired hotter and is denser and less porous than earthenware, which means less chance of the body absorbing odours over years of kimchi and an easier surface to get properly clean.
Be realistic about weight. Seven litres of cabbage and brine plus a ceramic crock is not something you will casually shift across a counter, so decide where it lives before you fill it.
Key Specifications
- 7 litre capacity
- A-grade porcelain, denser than standard stoneware
- Water-seal rim with fitted lid
- Weight stones included
Pros
- Large enough for serious garden volume
- Porcelain is less porous and easier to clean
- Holds odours less than earthenware over time
- Complete with stones
Cons
- Very heavy when full — site it before filling
- Takes significant storage space
- More expensive than stoneware of the same size
- Too big for a first batch
Best for Kimchi: e-jen Premium Fermentation Container with Inner Vacuum Lid
A completely different approach, and for kimchi specifically a better one. Instead of a water moat, the e-jen uses an inner lid that you push down directly onto the surface of the vegetables, pressing out the air between the food and the lid. It replaces the weight and the airlock in one part.
Two practical advantages over ceramic. It is food-grade plastic, so it is light and cannot chip — and it goes straight into the fridge, which is exactly how kimchi is meant to be stored after its initial ferment. Moving kimchi from a heavy ceramic crock into jars for the fridge is an annoying, messy step this design removes entirely.
It is also the only one here you can carry one-handed when full. The trade is that it is plastic, which will not appeal if you want the traditional object on your counter.
Key Specifications
- Food-grade plastic fermentation container
- Inner vacuum lid presses onto the food surface
- Fridge-friendly for storage after fermenting
- Popular design for Korean-style kimchi
Pros
- No separate weight or airlock needed
- Goes straight into the fridge after fermenting
- Light and unbreakable
- Genuinely the right tool for kimchi
Cons
- Plastic rather than traditional ceramic
- Inner lid seal needs cleaning carefully
- Can retain strong kimchi odours
- Less attractive on a counter
Best Glass: 2.5-Litre Glass Fermentation Jar with Water Seal Lid
The frustrating thing about a ceramic crock is that you cannot see inside it. For the first few batches, when you have no idea what is normal, that is genuinely unnerving — you are waiting two weeks with no feedback except smell.
This glass version has the same water-seal moat and lid but lets you watch the whole process: the brine clouding, the bubbles rising, the colour shifting. For a first crock, that visibility is worth a lot of reassurance.
The counter-argument is real though. Light degrades some ferments and can fade colours, so glass crocks want a dark cupboard rather than a sunny counter — which slightly undoes the benefit of being able to see in. At 2.5 litres it also sits between jar and crock scale: one cabbage, comfortably.
Key Specifications
- 2.5 litre glass fermentation jar
- Water-seal lid, same principle as a ceramic crock
- Fully transparent
- Food-grade glass, non-porous
Pros
- You can watch the ferment, which reassures beginners
- Glass never absorbs odours
- Easy to check brine level without opening
- Cleans completely
Cons
- Needs storing away from light despite being transparent
- Smaller than a true crock
- Glass is more fragile than stoneware
- Weights often sold separately
Best Complete Set: Trademark Stoneware Fermentation Crock with Weights and Cabbage Tamper
This set includes the piece people most often forget to buy: a cabbage tamper. Getting shredded cabbage to release enough of its own liquid to submerge itself takes far more force than you would expect, and doing it with a fist or a wooden spoon handle is both ineffective and unpleasant.
A proper tamper — a heavy wooden pestle with a broad head — lets you pack a crock down hard and fast, and the difference in how much brine you draw out is immediately obvious.
Stoneware crock, weight stones and tamper together makes this the closest thing here to a genuinely complete first-crock purchase.
Key Specifications
- Stoneware fermentation crock with water seal
- Weight stones included
- Wooden cabbage tamper included
- For sauerkraut, kimchi and pickles
Pros
- Includes the tamper most sets leave out
- Everything needed in one purchase
- Traditional stoneware construction
- Good gift for a new fermenter
Cons
- Wooden tamper must be dried thoroughly after washing
- Heavier overall package
- Crock quality is mid-range rather than premium
Best Small: 3.8-Litre / 1-Gallon Stoneware Fermentation Crock
One gallon is the smallest size that still behaves like a crock rather than a large jar, and for a household of one or two it may be all you ever need. It takes a single cabbage comfortably, which conveniently is also the amount most sauerkraut recipes are written around.
The practical argument for starting small is storage and commitment: a one-gallon crock fits in a normal cupboard and is light enough to move full, so it actually gets used. A five-litre crock that lives on the floor of the pantry because it is too heavy to lift down does not.
One decent cabbage — around a kilo and a half — shreds down to surprisingly little once it is salted and pressed; I got a little over a litre of finished kraut from mine. That single number answers the size question better than any capacity chart.
A 5-litre crock sounds sensible until you work out that filling it properly takes roughly four cabbages, and a crock left half empty has too much air sitting over the ferment. My honest advice is to decide how much kraut your household actually eats in two months and buy that size. I over-bought first, and then spent a season making batches that were too small for the vessel I had.
Key Specifications
- 3.8 litre / 1 gallon stoneware crock
- Water-seal rim design
- Takes roughly one cabbage
- Compact enough for normal storage
Pros
- Right size for one or two people
- Light enough to move when full
- Fits in a standard cupboard
- Cheapest true crock here
Cons
- Too small for garden-scale batches
- Water channel is shallow and dries out faster
- Weight stones may be sold separately
The Ultimate Buying Guide for Fermentation Crocks
How a Water Seal Actually Works
The rim of a fermentation crock has a channel or moat running around it. You fill it with water, and the lid sits down into that water rather than resting on the rim. The result is a one-way valve made of nothing but liquid: carbon dioxide produced by the ferment builds up, pushes down past the lid and bubbles out through the water, and the water immediately closes behind it so no air can travel the other way.
There is nothing to fail, nothing to remember, and no daily burping. The only maintenance is topping up the channel as the water evaporates — roughly weekly, more often in a warm dry room. If the channel runs dry, the seal is gone and oxygen gets in, so it is worth putting somewhere you will see it.
Crock or Jars? An Honest Comparison
- Jars are cheap, stackable, visible, easy to store and go straight in the fridge. They cap out at about a pint of finished kraut each, and one cabbage means several jars and several weights.
- Crocks take whole cabbages, need no burping at all, block light, and hold a more stable temperature because of their thermal mass. They are heavy, expensive, opaque, and you have to decant the results into jars afterwards anyway.
Most people should start with jars and buy a crock once they know they will keep doing it.
What Size You Will Actually Use
This is where people most often get it wrong, almost always by buying too big.
- 1 gallon / 4 litres — one cabbage. Right for one or two people, and light enough to actually get used.
- 5 litres — two or three cabbages. The sweet spot for most households and the most popular size for good reason.
- 7 to 10 litres — four or more cabbages. Only if you have a garden producing at volume, or a large household.
- Above 10 litres — genuinely difficult to move, fill, empty and clean. Buy two smaller crocks instead, so you can run two different ferments at once.
A crock also needs to be at least three-quarters full to work properly — too much headspace means too much trapped air. An oversized crock half-filled is worse than a small one packed tight.
Stoneware, Porcelain or Plastic
- Stoneware is the traditional material: heavy, opaque, thermally stable, affordable. Check the interior glaze for chips and crazing, and avoid damaged pieces for food use.
- Porcelain is fired hotter and is denser and less porous, so it absorbs odours less and cleans more easily. Costs more.
- Food-grade plastic (like the e-jen) is light, unbreakable and fridge-friendly, and uses an inner press lid rather than a water seal. Less charming, genuinely practical, especially for kimchi.
- Glass lets you see the ferment, which is reassuring early on, but needs to be kept out of the light anyway.
A note on glaze, since crocks are low-fired pottery like any other: buy from sellers who state their glaze is lead-free, and retire any crock whose interior glaze is chipped or crazed. The same reasoning we set out in our lead-free clay cookware guide applies here, and it applies more sharply because ferments are acidic and sit in contact with the glaze for weeks.
Weight Stones
Most crocks use two half-moon stones rather than one disc, and that is the better design: two pieces fit through the opening easily, lie flat across the vegetables, and can be lifted out one at a time from a full crock. Check whether stones are included before buying — they are a significant extra cost bought separately, and a crock without them cannot do its job.
Where to Put It
- Cool and stable — roughly 60 to 70°F is ideal. Warmer ferments faster and can go soft; colder is slow but fine.
- Out of direct sunlight. Ceramic handles this for you; glass does not.
- On a tray. Active crocks push brine out of the water channel. It will happen.
- Where you will see it, so you remember to top up the seal.
Cleaning a Crock
Hot water and a brush. Avoid strong detergent on stoneware, which is slightly porous and can hold the taste. For lingering smells after kimchi, a soak with a solution of baking soda, or a rinse with vinegar, usually clears it. Dry thoroughly before storing, and store it uncovered or with the lid ajar so trapped moisture does not go musty.
Frequently Asked Questions About Fermentation Crocks
Do I need to top up the water in the seal?
Yes, roughly every week or two depending on how warm and dry your room is. If the channel runs dry, the airtight seal is broken and oxygen can reach the ferment, which is when mould becomes possible. It takes five seconds; the only difficulty is remembering, which is why a crock is best kept somewhere visible.
Can I use a regular ceramic crock without a water seal?
You can — open crocks are the older design and still work — but you will need to skim the surface regularly, because without a seal air reaches the top of the ferment and kahm yeast or mould forms there. A water-seal crock is simply less work and more reliable. If you use an open crock, keep everything well below the brine and check it every few days.
How much sauerkraut does a 5-litre crock make?
Roughly two to three medium cabbages, which after fermenting and packing down gives you somewhere around four to five quarts of finished kraut. A 1-gallon crock takes about one cabbage. Remember a crock should be filled to about three-quarters, so plan cabbage quantity around that rather than the stated capacity.
Is white film on my ferment mould?
A flat white film is usually kahm yeast — harmless, though it can give an off taste if left. Skim it off and make sure everything is under the brine. Fuzzy growth of any colour, including white, is mould, and that batch should be discarded rather than scraped and salvaged. A properly sealed water-seal crock rarely gets either.
Can I ferment in a crock in a warm kitchen?
You can, but it ferments much faster and the texture suffers — vegetables can go soft and the flavour turns sharp before it develops any depth. Around 60 to 70°F gives the best results. In a hot climate, a basement, garage or the coolest cupboard in the house is usually a better home than the kitchen counter.
Do fermentation crocks contain lead?
Reputable modern crocks are made with lead-free glazes and are sold as food safe. The risk sits with antique crocks, unmarked imports and pieces with damaged glaze. Buy from a seller who states the glaze is lead-free, and retire any crock whose interior is chipped or finely cracked — ferments are acidic and sit against that surface for weeks, which is exactly the condition that draws lead out of a compromised glaze.
Final Thoughts
For most people the TOMO crock is the right buy — correct size, a well-made water channel, and the weight stones included rather than sold separately. On a budget, the SEEUTEK 5-litre uses the same principle for less. And if kimchi is what you actually make, the e-jen is a better tool than any ceramic crock, whatever it looks like on the counter.
Buy smaller than you think, keep the water channel topped up, put it somewhere cool and dark, and stand it on a tray. If you are not yet at crock scale, our mason jar fermentation kit guide is the place to start.
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Rimi Sultana is a home cook from Bangladesh who has cooked for her family every day for the past five years and writes about it at Smart Cooks. Perpetually testing whether internet-famous recipes actually work in a regular home kitchen. Say hello on Facebook or through the contact page.