Clarifying vegetable fermentation

Fermenting is an ancient way to preserve food for long term use without refrigeration, while creating great flavour and increasing the nutrients and digestibility of the food.
But starting to ferment vegetables can be very confusing, even a little scary, and asking questions in online groups may make the problem worse instead of better.

The internet is awash with bad instructions for fermenting, and errors compound like a mold-growing game of telephone.

More confusion arises because there are a couple of major groups of fermenters with different—and often unstated—fermenting goals. The different goals favour different equipment and techniques, but since the groups are not identified, the differences just create confusion.

Questions about fermenting containers and covers are usually met with Brand Name is the BEST!! without a discussion of the important factors or tradeoffs as to why the container works for that person.

And there is a growing movement for measuring salt in a different way, but the techniques are not identified and don’t have a common name in use online.

In this article I will identify and clarify as much of this as I can:

  • Different goals of fermenting
  • Why use an airlock
  • Other gear suggestions
  • You can use any salt
  • Tap water is probably fine
  • Botulism is unheard of

Different groups have different goals

The original use of fermentation, in addition to making delicious food, was to preserve harvest bounty for long term storage. This may not be obvious to those of us living in industrialized societies where food seems to magically appear in grocery stores, but many of the dishes created in different cultures around the world have this unstated goal of preserving a short-lived bounty for later use, time-shifting our labour into the leaner months.

One of the main techniques is to ferment the food to create a high enough level of acid, below a pH of 4.6, that spoilage or pathogens can not grow. Milk ferments into yogourt, cabbage into sauerkraut, fish into garum. Sugars ferment in sausage to make acid that prevents spoilage while the sausage dehydrates below the level that spoilage can grow. Apples become cider.

So, fermentation allowed us to store abundance for later use, by transforming it into shelf-stable foods. Shelf-stable is not the same as “lasts forever”. No food lasts forever, and it is normal for shelf-stable foods to degrade in texture, appearance, and nutrition over time. However, they should not make you sick.Milk might sour in a few days, but cheese can last for years. Vegetable harvests might freeze in the fields, but pickles will keep over the winter. An annual fish run can be preserved in bottles of umami-rich sauce.

The folks with this goal are looking to get massive amounts of food processed and into the root cellar. They don’t want fussy or fiddly, and they have a thousand other things to do every day in harvest season.

On the other hand, a lot of people who ferment today approach it as a hobby. It is fun to do, and it makes delicious food. They may be less tied to seasonality. They may use it more as a condiment and less as a staple food. Some folks are using ferments to enrich their gut flora to treat digestion issues. There is much less emphasis on fermenting to a level of acidity that will preserve the food, and so ferments may be refrigerated after just a few days.

Without the mad pressure of harvest season, these folks often have an enviable intimacy with their ferments. They might leave them on the counter, and taste them every day or two. Maybe they like glass crocks, so they can watch the bubbles and colour changes as the process progresses. 

These two groups have different goals from beginning to end, and so they make different choices. Without understanding what drives those choices, a lot of the advice seems like conflicting information. Once you identify your goals, the choice of equipment and technique becomes a lot easier.

Let me introduce myself—I am in the first group. I want to preserve the wild abundance of harvest season for eating over future months. I am too busy at harvest time, and do not want to screw around or use equipment that will allow my carefully tended veg to spoil.

Airlocking is a good idea.

One of the worst bits of the moldy game of telephone are recipes that say you should use coffee filters, towels, or whatever to cover your ferments.

I first fermented sauerkraut in a crock—and it grew mold over the surface. So then every day I was opening the crock to skim off the mold and Kahm yeast. I now know that mold was growing because there was too much oxygen in the crock, and every time I opened the crock to skim off mold I gave the mold a fresh blast of oxygen. Humans have eaten a lot of moldy food over time, but this is not my goal with pickled veg.

Mold and yeasts that infect veg ferments need oxygen. The lactobacillus that ferments vegetables can live with oxygen, but are just fine without it. So, it works very well to airlock the ferment to make life difficult for mold and yeasts. You need to vent the gas produced during fermentation so the jars don’t blow up, but you don’t want to let any oxygen in.

There are a lot of different ways of airlocking.
According to Lance Hancherow, a fermentation historian, the traditional crock was used with many layers of material which all added up to be a reasonable airlock, just like the Swiss Cheese Model of infection control. First there was brine over the veg, then a weight, then a couple of layers of cheesecloth floated on the surface, then a waxed cloth cover, then a lid. You would open it up periodically and peel off a layer of moldy cheesecloth if needed, then replace the waxed cloth and lid.

When you think about the context, the creativity and effectiveness is impressive. Until very recent centuries, most humans lived very local and handmade lives. There was not a lot of international or global trade, and many people could go their entire lives without every having a piece of “money”.

So, a crock, made from local clay and fired locally, a weight from a boiled river stone, some cloth, and some wax—all locally made or collected—made an effective airlock system—though one that required care and maintenance.

Our context today is quite different. We can buy airlocks for a few dollars. Glass jars finer than were ever used by royalty are mass-produced and available in our hardware store. You can ferment with a plastic bag, a bag within a jar, a mason jar with a soup can weight on the lid, a Fido jar, or all sorts of fermenting lids and hardware.

I think our ancestors would happily use their crocks to hold umbrellas, as I do, and use some of the amazing and affordable equipment we have today. Just do not use a coffee filter or tea towel with veg ferments—or if you do, expect to spend more time and still get a higher rate of moldy ferments.

Fermentation takes time, and the time is temperature related.

Fermentation takes time. Using Sauerkraut as an example, pH may not drop below 4.6 for four to six weeks, especially if you are fermenting in a fairly cool place to favour the best flavours and textures.

Sauerkraut has three or four bacterial successions. The first one barely makes any acid—but even that little bit poisons the bacteria that made it by making the environment inhospitable. The second bacterial species produces a lot of acid, and also a lot of gas, which is why airlocks are so helpful to allow venting. Eventually it too cannot survive in the increasing acidity. A final species flourishes and wraps up the acidification.
Dill pickles might take ten days in a warmer area, and they are then moved to a cool spot for the higher level of salt to equalize throughout the food.

So, a recipe that ferments for just a few days is not using fermentation for preservation. This is fine. Curtido is a quick cabbage ferment from El Salvador that builds a tang over two or three days, creating a delicious side dish but not one that is shelf stable. If you don’t like your pickles to have so much bite, go ahead and use the fridge for the preservation function. The cool temperatures will slow the fermentation almost to a stop, allowing you to enjoy the low level of acidity and simple flavours.

But if you want to ferment to preserve food without refrigeration you need to allow the process to complete to the point that there is too much acid for the spoilage to grow. Airlock it well so oxygen does not get in, and then leave it alone.

Any salt works

You can use any salt for fermenting, so don’t worry about buying the fancy stuff. You can even use iodized table salt. Some people can taste iodized salt, and it may cause brines to go cloudy, which is considered an aesthetic fault but is not dangerous at all. You won’t notice cloudiness with solid ferments like sauerkraut.
You can also substitute Pickle Crisp for 25% of the salt. Pickle Crisp is simply a different kind of salt, Calcium Chloride.

I also weigh my veg and my salt. One of main reasons for weighing salt is that different salts can vary substantially in density, so a tablespoon of kosher is a different weight from a tablespoon of coarse.
Humans have been fermenting for millennia without scales—but there are lots of things our ancestors would have happily used if they had it, like Gore Tex jackets, steel nails, and rubber shoe soles. I bet they would have been happy to use affordable digital scales.

So, you definitely can ferment without a scale, but weighing your ingredients allows you to replicate recipes you like, control sodium levels for health reasons, and successfully ferment different kinds of veg that require different salt levels.

Personally, I also use scales for baking, and I have a jeweller’s scale for weighing the nitrites and nitrates used in meat curing, which are dangerous if overused—so, I have scales and I use them for fermenting too. I also bought a set of scale weights for a de-industrial future.

A method that is growing in popularity is to measure salt based on the total weight of water and veg. This makes fermenting super easy and fast.

This is a familiar method in other areas—when curing meats this total weight method is called an Equalization Cure. This total weight is of course how we make sauerkraut, but it is slightly different from the traditional pickling method of making a generic brine.

Here is another way to thing about it:
When we cook a roast, we put it in a hot oven, and try to guess when enough heat has made it to the centre of the meat—we apply way too much heat, and try to pull it out before the meat is dry and tough.

On the other hand, when you do sous vide cooking you just cook at the temperature you want, so if you want your roast to be 135F, you cook at 135F.

Fermenting pickles is the same. The old way is to make a brine that is too salty—a 5% brine is common—and hope the right amount of salt infuses our cucumbers. If our cukes are different sizes there will be different amounts of brine in the jar, and therefore there will be differant amounts of salt in each jar—so we get variable results from jar to jar.

On the other hand, when you use the total weight method, you simply add the amount of salt you want to get, so when you add 3.5% of the total weight of veg and water you know you are going to end up with 3.5% salt in the cucumber.

I don’t see any reason to not use the total weight method, but most recipes assume you are going to make a generic brine, so you need to watch out for that.

I have also moved away from premixing brines. Fido jars are such an effective airlock system I can be less meticulous about controlling spoilage. I just weigh the salt and dump it on top. 

All of this math is easier when using grams, and a scale.

Here is a chart for the amount of salt to use for the Total Weight method, from the excellent Cultured Guru website. 


I use tap water. Our town has good water that does not taste of chemicals, but it is treated with chlorine and chloramine. I have tried boiling to get rid of the chlorine and adding lemon juice to react with the chloramine—but mostly I just use it straight from the tap. It works fine; I have never had a ferment fail to start.
If your water does not taste good or smells strongly of chemicals you may need to put in a bit more work.


Botulism is the scariest word in food preservation, but cases of botulinum toxin poisoning are very rare. Fred Breidt, USDA specialist, said: “There has never been a documented case of foodborne illness from fermented vegetables. Risky is not a word I would use to describe vegetable fermentation.”
In North American most cases of botulism come from improperly processed canned meats, and the majority of those cases occur in Alaska.

Of the remaining few cases, there is some risk to storing garlic in oil at room temperature, where the bacteria are warm and anaerobic. Never do this. However it is safe to use garlic in fermented foods because fermenting creates acid which is inhospitable to botulism.

Other Spoilage

What is common in ferments that are not properly airlocked are molds and Kahm yeast.

Mold is not good. Some people have very strong allergies to mold, even in tiny amounts—and by the time you see the mold on the surface it has grown roots deep into the food. Throw the food away, and improve your airlock next time.

Kahm is a delicate film of yeast that grows on the surface of the brine. It is not harmful, but some people don’t like the taste and it is considered an aesthetic flaw. With veg ferments, again, you need to improve your airlock. You can skim the Kahm off and eat the veg if the flavour does not bother you. It is very difficult to get rid of Kahm in a jar of veg once it has started.

When making vinegar the second stage needs oxygen, and it can be very difficult to prevent Kahm from colonizing.

If you don’t see mold, but are still scared of what might be growing in your adventurous ferment, the best thing might actually be to leave it longer. It can take six weeks for a ferment to stop producing acid, depending on the temperature it is at. Below a pH of 4.6 spoilage cannot grow, so give it time to acidify.

Fermenting vessels

So after all that…

I ferment to preserve the abundance of seasonal harvests, and I use Fido jars. I have been using them for almost a decade, and I have never had mold on kraut or dill pickles. They are very affordable, and you can buy many times the volume of Fido jars as you would get by spending the same money on a traditional crock—and you will get much better results.

I think Fido jars are an earth-shaking innovation—which I only half-jokingly compare to the printing press.
I have stored kraut for a year and dill pickles for five years (oops), unrefrigerated, in our back room.
We live what we call a Small and Delicious Life, and that means that it feels like every day has a thousand tiny tasks to do—seed, harvest, can, cure, press…some step of vegetable, meat, or cheese production that needs attention.

This is a lot of work, and it takes a lot of brain energy to track all these thousand tiny tasks. So, I am very enthusiastic if I can just completely eliminate tasks so I don’t need to think about them at all.
Flip-top jars eliminate 99% of the work of fermenting in a crock, and at least 80% of the work of fermenting in mason jars. There is no burping. You don’t need weights, springs, pumps, valves, or modifications.

So, I have become a Fido proselytizer.

Fido jars are European canning jars. They are used for water bath canning in exactly the same ways we use two piece metal lids in North America. They are designed to be food safe, and to vent gas in the canning process.

Canning jar brands include Fido, Kilner, ARC, Le Parfait, and even IKEA’s very affordable Korken line of jars (which are slightly lighter weight, but still work well).

Do not use dollar store decor jars, due to uncertain glass composition, potentially inappropriate gaskets, and uncertain wire adjustment.

The big thing about Fido jars is that they burp themselves, so you don’t need to mess with them until you are ready to eat.

Unlike the plastic bubbler airlocks like are used for wine, the clamp system means Fido jars slightly pressurize. They form a serious blanket of CO2 on top of the food that really prevents mold.

Here is a video showing how Fido jars vent

And here is a video showing how you can check a jar for correct adjustment. I have never had to adjust a new Fido jar, though I have adjusted different brands I bought at the thrift shop after I put a new gasket on.

For the folks who are not concerned with easy storage of the harvest for winter, I think the Easy Fermenter-style lids with the pump are a good choice for this group. These lids allow you to open the jar mid-ferment and taste the contents, then pump out a bunch of the oxygen you just let in.

Another old school method is to ferment in mason jars, burping the jar once or twice a day during the gas production phases of fermentation so the building pressure does not blow up the jar. This is a little stressful, so you can make mason jar fermenting easier by simply putting a can of soup on the lid instead of using the ring. You want that pressure to build a bit before the jar burps, so the weight on the lid does that.

This is an airlock upgrade but it is a little fussier because you don’t want to knock your soup can off accidentally. It is harder to move around in your pantry. But it works well.

Here is Lance’s method for fermenting in a plastic bag.

And his free and excellent method that uses the weight of water to seal and hold the pressure. If I wanted to make 30 gallons of sauerkraut, this is how I would do it.

For kimchi fermentation, the Korean fermenting boxes are an amazing mix of high-low tech—clay is mixed with plastic, to create a slightly porous container.

I would encourage you to avoid the Pickle Pipe style of silicone lid. In fermenting groups this style is the most common source of spoilage—they seem very sensitive to correct installation. This is a shame, as I had hoped they would be an affordable and effective way to ferment in mason jars.

Lazy pickles

Here is how easy it is to make a jar of dill pickles.
I do not sanitize or sterilize my jars, I just wash them with soap and water and store them empty with the lids closed, with the gasket removed and left inside the jar.

  • weigh the Fido jar
  • add a few grape leaves for tannic astringency, a big handful of dill weed, some garlic cloves, and a few peppercorns
  • wash your cukes and trim ⅛” off the blossom end to reduce enzymes that cause softening. Pack the jar to the shoulder. It is tempting to cut into spears to get more in a jar, but I find they get soft faster, so I don’t cut them anymore.
  • fill the jar to the shoulder with water
  • weigh the jar again and subtract the weight of the glass
  • multiply that total weight of veg and water by 3.5%. So, if your water and veg are 1000 grams, you add 35 grams of salt.
  • just dump the salt into the jar. Yes, it is that easy.
  • put a new or soft and uncracked gasket on the jar and seal it. As shown in the videos above, it will self-burp.
  • swirl the jar a couple of times to wash the salt down.
  • set the jar in a dish to catch overflow from the vigorous gas production phase of fermentation, and put it in a warm, dark place.
  • after a few days move it to a cool place. Not freezing, but as cool as you have.
  • refrigerate after opening.

That is all there is. This takes me five minutes to make a big jar of dill pickles.

Because Fido jars are such an effective airlock system, I have not used weights in almost ten years, which again is easier and cheaper. I always have cukes poking up out of the brine—like poking up a lot, they do not need to be submerged. My sauerkraut usually reabsorbs the brine and looks dry. No problem and no mold.
And as I said, I have eaten excellent sauerkraut that was left for a year in our unheated back room, which is cool in the winter and too warm in the summer.
I have left dill pickles for five years. They were too soft for good eating, but they tasted great and were not spoiled, so I used them to make pickle soup.

Fermenting is an ancient and diverse set of technologies to safely and effectively preserve food. Fermented vegetables are delicious, safe,More advanced ferments, like meat, fish or sauces, can be dangerous if done improperly, so seek out cultural knowledge-keepers if you are going to advance to these foods. nutritious—and can be very easy and rewarding to make.

If you would like to read more, please enjoy How to make Sauerkraut or pickled vegetables the easiest and cheapest way possible, or watch my short Introduction to Sauerkraut.


  1. Thank you for this, Ruben. I have been making sauerkraut in a crock, but I will definitely stock up on Fido jars.

    • Thanks for reading Joe, good to hear from you. It would be interesting to hear more about your crock experiences—what temperatures, how long, do you get mold etc. The thing I love about fermentation is the transformation—it seems magical. From juice to cider, from raw meat to sausage, from flour to bread. Wizardry.

      • I have only fermented two things, honey, water and champagne yeast to make mead and cabbage to make sauerkraut. I made about 20 gallons of mead from my own honey at the beginning of the pandemic, but then my wife and I stopped drinking alcohol so I have about half of it left.

        I ferment the cabbage in a ten-liter crock. The crock has a moat around the perimeter of the opening which holds water and the lid rim rests in the moat so there is a water seal at all times. I use 2% salt by weight and plain coarsely shredded cabbage. Nothing else. Everything is tossed together and then the cabbage is stuffed in the crock and weighed down with ceramic weights that came with the crock.

        I live in a subtropical environment and my house is usually between 65 and 75F. I do nothing for about a month except top up the water in the moat. I then take out the sauerkraut and pack it in quart jars and store it in the refrigerator. I’ve never had the slightest mold or yeast and the fermented cabbage is delicious.

        I like the idea of the Fido jars, because the ferment never has to come into contact with the air until the jar is opened to eat the contents. I could probably leave the kraut in the crock at room temperature for a long time too, but if I want to eat any I have to break the airlock and risk mold spores getting into the crock.

        Just so I am clear about your method: do you snap the lid bale down tight into its normal closed position after loading the jar or do you do something else to make it easier for the gas to escape? Has a jar ever blown up? I watched the video, and they snapped the bail all the way down, but it wasn’t clear that the gasket was a normal gasket. In the video the jar seemed to leak out gas very easily. It’s a wonder they are air-tight in the other direction.

        • Joe, you snap the bail tight on the jar.

          I have never had a jar blow up, and out of many years in several different facebook groups, one of which was entirely dedicated to Fido fermentation, I have only heard of two people who had a jar explode. In both cases they were fermenting sweet things—one was kombucha, and the other I think was beets. So, my theory is that the gaskets got glued shut.

          But, it may also be that they had swapped gaskets or parts or something and so the adjustment was too tight for venting—it is hard to know.

          Fidos actually hold surprisingly little pressure. There is another video on youTube where a guy drilled a hole in the lid and put a pressure gauge in the hole, then did the same baking soda and vinegar mix. If I remember correctly the pressure the jar vented at was only a third of a pound per square inch.

          While I have never had to adjust a new Fido, I have tested them often, as shown in the adjustment video—put some water in the jar, seal it, then turn it upside down and try to pry the lid off sideways. You should get a dribble of water.

          The gaskets shown are stock Fido gaskets, and they sell replacements, as do most of the European canning jar companies, though some can be harder to find. I use Fido gaskets on every brand of jar whenever I feel I need a new gasket. Mix and matching brands like that does sometimes necessitate adjusting the bail.

          But, if you buy Fido jars and replace the gaskets with Fido gaskets as they age you will likely not have a problem for years and years.

          The water moat crocks are excellent, the best option for a crock, but I bet you will enjoy Fido jars.

          The warm tropics are not the environment that sauerkraut was developed in. I wonder what the local fermenting traditions are—perhaps sauces? Anyhow, depending on what you grow or get in the market, you might enjoy making other pickles too—carrots sticks are excellent.

          Do you have a cellar, or a well, or some place you could access the cool temperatures underground? Your kraut will stay crunchy longer if it is cool. Your fridge is great of course, as long as you have room for it. Fair warning, some people get hooked on fermenting and end up buying a second fridge!

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