Inside and Out: Vessels for Fermentation
Clay fermentation vessels.
As long as humans have been fermenting vegetables, legumes, meats, grains, and fruits, they’ve needed a vessel to contain their creations. Some ferments require protection from the ambient air and its native microbes, while others depend on this contact for the process to work. As American architect Louis Sullivan famously said, “Form follows function,” and we see this in the case of the underlying materials used in fermentation vessels. So, let’s explore fermentation vessels through the materials used to make them, so you can confidently choose the right one for your next ferment.
Clay crocks and pots are the classic fermentation vessel, and for good reason. They come in two basic forms: One has straight sides with an open top, while the other usually has more rounded sides with a lid that fits over its opening. Weighting down your ferments in straight-sided crocks is as simple as finding something round that fits the inside area, such as a salad plate, and placing something heavy on top of it. For the more rounded crocks, the weights need to pass through the narrower opening on top and then cover a wider surface inside. To accomplish this, they often come with split weights, meaning the round weight is a piece of ceramic that’s split in two down the middle, so each half can easily fit through the narrow opening and then reassemble on top of the ferment.
When our family began fermenting vegetables in the late ‘90s, the only new crocks available in the United States were straight-sided, lidless crocks from the Midwest, sold through specialty catalogs that catered to homesteaders and back-to-the-landers. With the renewed interest in all types of fermenting, that’s thankfully changed. Today, you can find artisan potters riffing on classic styles with innovative glazes, shapes, and sizes, as well as time-tested commercial versions from all around the world: classic European water-seal designs with gorgeous glazes from Mudslide Stoneware; open crock styles from fermentation enthusiasts, such as Ogusky Ceramics; a variety of commercial sizes of water-seal styles from Germany’s Harsch or Poland’s Boles?awiec; and straight-sided styles from America’s own Ohio Stoneware. There are also traditional Asian styles, such as the beautiful handmade Onggi pots of Adam Field.
Crocks are beautiful and time-tested; they provide temperature control for your ferments and can last for generations when properly cared for. However, they’re usually heavy and costly. When we produced vegetable ferments commercially, we used a dozen 10-gallon monsters from Ohio Stoneware that were more than 100 pounds when full of ferments. That’s a lot to lift, but they helped us consistently produce large batches of quality fermented vegetables. If you want to make batches of a gallon or more, and beauty is important to you, clay crocks and pots are a worthwhile consideration.
Glass fermentation vessels.
Glass jars, jugs, carboys, and bottles are great for ambient fermentation because they’re inexpensive, easy to clean, surprisingly strong, and happy to show you what’s going on inside. Being able to watch your ferment is especially helpful for those new to fermentation. For vegetable fermentation, glass jars will afford you the opportunity to make smaller batches, which is great if you’re just starting out, or if your garden is only producing spurts of veggies. For small jars, make sure you have a weight that’s heavy enough to keep the veggies below the brine line (the No. 1 tip for a successful fermentation). For fruit wines and hard ciders, I recommend 3-gallon glass carboys; they’re light enough to move around the kitchen when full, and hold enough ingredients to make the effort worthwhile come bottling time. For ferments that are particularly sensitive to light, keep glass jars away from windows and direct sunlight.
For larger multi-gallon batches, big glass crocks — such as those from Anchor Hocking — will really showcase what you’re fermenting. Glass will become less efficient when you divide your batch among many small jars; you’ll end up monitoring a counter of jars of the same ferment, each with its own needs. For larger batches, it’s worth moving up to crocks, barrels, and buckets.
Wooden fermentation vessels.
Like clay, wood has been fashioned by humans to make and transport fermented foods for thousands of years. Staves of wood banded together produce very strong vessels that, when built as a barrel (closed to ambient air), are easily rolled and stored. As open vats (open to ambient air), they hold massive quantities.
In Japan, cedar is preferred for making the trays that are used to grow koji — a mold used to make things such as miso — because of its ability to absorb small amounts of water and its resistance to mold and rot. Traditional miso vats are also made from cedar and range in size, from our beloved 5-gallon vat to monsters of more than 1,000 gallons.
Oak barrels are famous for the fermentation and maturation of wine and vinegar, as well as aging distilled spirits. People who make craft beer and cider love to find used spirit and wine barrels for maturing their ferments as well. The constant competition makes used barrels increasingly difficult to find, and more expensive. Some barrels are also finding new lives as garden planters and funky furniture, making them even more elusive.
Wood imparts flavor to the ferment it contains, which, in the case of wine, beer, cider, and vinegar, is a very good thing. The challenge with using wood is that, unlike most clay, glass, and plastic vessels, wood is microbe-friendly. Under the right conditions, wood can harbor yeast, mold, and bacteria for months. If those microbes are the right ones for your ferment, they’ll jump-start the fermentation. However, if these colonists are microbes of the spoiling variety, they can ruin a perfect ferment. If you’re lucky enough to find a sound wooden barrel or open vat to use as your fermentation vessel, it’s worth taking the time to soak and sanitize it first. Wood is also beautiful, and can last for decades when properly maintained.
Plastic fermentation vessels.
Perhaps no material is more functional than plastic for its ability to mold to an exact shape, as well as its longevity. Plastic deserves consideration, but with a caveat: When it comes to active fermentation and storage, not all plastics are applicable. As a general rule, the more flexible a plastic is, the more volatile it is chemically. For example, common plastic wrap exchanges more synthetic ions than a milk or water jug, which in turn exchange more synthetic ions than a rigid plastic bowl or bucket. Two compounds to watch for are polyvinyl chloride (PVC), a chemical typically found in plastic wraps, and bisphenol A (BPA), often included in select resealable bags, and was once present in baby toys. There’s still argument over whether any type of plastic is safe for holding higher-acid ferments, such as vinegar, sauerkraut, and kimchi.
If you’re making large batches of fermented vegetables or fruits, it’s tough to beat recycled 5-gallon buckets or 1-gallon pickle or mayonnaise jars for practically no expense. In fact, in craft beer, wine, and cider businesses, many makers use “blue oak” — food-grade barrels made of blue plastic used for importing products, such as olives and olive oil.
Put a Lid on It
Most ferments require that you manage the ambient air around them, either allowing it to contact the surface of the ferment (as with vinegar) or keeping it out (as with wine and cider). If you’re allowing the air in, natural materials, such as cheesecloth or clean tea towels, are a permeable solution; they
allow air exchange while keeping bugs and dust out. Lightly packed cotton wads in the narrow mouth of carboys and bottles have the same effect as a cheesecloth. If you need to keep oxygen away from your ferment, a lid will allow the gas produced in fermentation to escape, but will block any invaders from the outside. If you’re making legume ferments, such as miso, or if you’re making small-batch vegetable ferments, a tight-fitting lid will do the job. Any gas produced can be easily released with a “burp” by quickly loosening the lid and then retightening it after permitting the pressured gas to escape.
There have been huge strides of innovation in sealing and protecting ferments in the past decade, including new takes on the classic water moat and one-way air valve systems. These devices allow the pressure within to push carbon dioxide out through the water without letting ambient air from the outside back in through the same watery path.
The variety of vessels, lids, and complete systems produced today by small artisans, entrepreneurs, and large traditional brewing or canning companies makes this the opportune time to jump into fermentation. The options can be overwhelming, so start simple, find what works for you, and explore the edges of your style. You’ll find something that best suits your aesthetic, temperament, style of cooking, and lifestyle. The vessel you choose now may become a family heirloom filled with stories of your famous ferments, passed down for generations
Christopher Shockey and his wife Kirsten are the coauthors of three best-selling fermentation books, including their newest release, Miso, Tempeh, Natto and Other Tasty Ferments: A Step-by-Step Guide to Fermenting Grains and Beans for Umami and Health. They teach worldwide and host workshops on their homestead.
Stay True to the Brew
Let your brew recipe inform your equipment choices and get great beer with little to no extra cost.