Cap Uses

Fermenta Lock is a compact airlock cap for mason jars, to help in making old fashioned brined pickles, and other lacto-fermented foods. Use Fermenta Lock for:


Pickles (all kinds)
Sauer Kraut
Milk Kefir
Bean Paste/Hummus
Sourdough Starter (if started with culture or yeast)
Anything which needs gas release without a lot of air circulation.

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Aerobic and Anaerobic Myths

As the debate rages over whether fermenting should be done with an airlock, or without one, we keep hearing many myths repeated over and over concerning anaerobic bacteria and aerobic bacteria. There are many - repeated by people who have not followed the science through to its logical conclusion, or who have simply read something on a website produced by someone selling an airlock system, and have believed it, without realizing that only half of the story is being told.

Ok... so lets see if we can address some of the issues.

Myth: Pickles require an anaerobic environment, so they need an airlock. This is false.

Fact: Pickles merely require that the food be kept below the brine in order to ferment properly. It is the BRINE that does the fermenting, not the presence or lack of air on the surface.

Myth: Kefir must be fermented in an airtight environment. Completely false.

Fact: Kefir ferments wonderfully in any kind of container, lidded or not. It was traditionally fermented in skin bags, which were not airtight - if they had been, they would have exploded, because kefir releases a LOT of gas as it ferments.

Myth: Air moves through water, so the brine is not anaerobic. This is completely irrelevant.

Fact: It has nothing to do with good pickling. The salt in the food inhibits the growth of microbes other than the desired ones, or cultures put into the food grow faster than opportunistic cultures (yogurt and kefir) and create an acid environment before the harmful microbes can get a foothold. Acid then prevents the harmful microbes from multiplying in sufficient numbers to cause harm. This is true in open fermented and in airlock fermented foods. The presence of air is only relevant on the surface, not under the brine, due to the acid, and the high salt. Salt further inhibits air movement through the water.

Myth: Alcoholic Beverages are fermented using airlocks so it must be better. This is also false.

Fact: First, alcoholic beverages were traditionally fermented in either open vats, or in barrels with a hole at the top to let gasses and scum out (and many are still fermented this way). They were done this way for more than 6500 years. Airlocks have only been used in very recent history, and are still not used in all brewing, and are typically only used after the initial ferment is established. Besides that, the goals of brewing and the goals of pickling are very different. One aims to concentrate alcohol, the other aims to preserve by the development of an acid environment. One is a high carbohydrate environment which seeks to use yeasts to turn sugars to alcohol. The other is a high salt environment which seeks to pickle and preserve the food by encouraging bacteria to create an acid environment. Indeed many alcohol ferments do NOT store well like pickled items do.

Myth: The best cultures are anaerobic. Far from true.

Fact: Actually, some of the most dangerous microbes in the world are anaerobic. In fact, the most deadly of all, botulism, is an anaerobic germ. It is happily inhibited by acid, so it is not a risk in most fermenting situations (it may be where oil is used on top of a ferment). It is the salt and acid environment, NOT the presence or absence of oxygen on the surface which keeps deadly germs from growing - both aerobic and anaerobic pathogens. There are plenty of good aerobic microbes, which don't proliferate well in most fermented foods (but they are responsible for the creation of apple cider vinegar and several other types of fermented foods - good aerobic bacteria!).

Here's a few of our unwelcome friends who are all familiar anaerobic bacteria:

  • Strep throat, Scarlet fever, necrotizing faciitis, rheumatic fever, urinary tract infections, pneumonia, dental caries, the plague & meningitis are all caused by facultative anaerobic Strepptococcus species.
  • Clostridium spp. that cause intestinal gas, gangrene, botulism food poisoning, & tetanus.
  • Bacteroides spp causes abdominal & liver infections.
  • Fusobacterium spp that cause abcessing wounds, pulmonary or intercranial infections.

Just because they are anaerobic does not mean they'll grow in your ferment, UNLESS you fail to follow good fermentation rules (salt brine on veggies, and keeping the food under the brine). The point here is that claims that anaerobic bacteria are good, and aerobic bacteria are bad, is completely false.

Myth: Water lock systems are "airtight". This is false.

Fact: Waterlock systems allow the passage of air BOTH WAYS. They simply provide a slight pressure barrier which does not allow the FREE CIRCULATION of air. As long as the air pressure inside is greater than the air pressure outside, the system releases air only in one direction (which it will do when a proper ferment is established - it will release carbon dioxide which will increase the pressure in the jar). Brewer instructions on the use of waterlock systems recommend that the water lock be filled with something other than water, in case it is "accidentally" drawn in, instead of out. It does happen, even under circumstances in which it theoretically should not (usually because of failure to produce a proper ferment). Further, air moves through water - slowly - and the water lock is filled with water. It is not much, and it is slow, but it does move into the container this way. Some air will always be introduced through the waterlock, simply because it IS a waterlock. This information does not apply to a one-way valve, it does not allow air back in unless outside air pressure is MUCH greater than inside air pressure, because a one-way valve is designed to tighten the seal when outside pressure increases.

Myth: Airlock systems have to be airtight. This is false.

Fact: It is not necessary that they be airtight, only that they allow air release in a way that does not allow air circulation in both directions. This means that the jar lid does not need to seal tight - it only needs to provide sufficient seal to not allow free air circulation in an equal pressure environment. And that doesn't take much! A canning lid will do that just fine (in general, even a plastic one). The difference between holding air under pressure, and holding air with no pressure, is dramatic. It does not take much of a seal to hold under zero pressure difference. Some people fear that if the edge of the lid is not airtight, that air will circulate there while pressure is released from the airlock. Again, irrelevant. Air pressure is equally high THROUGHOUT the entire container. This means that even along the edges, if air pressure is greater INSIDE than OUTSIDE, air will move only one way - out. An airlock always requires a minimum degree of pressure from inside prior to releasing gas - so under proper fermentation conditions, the pressure inside should always be greater, meaning air will only move one way through other small gaps as well. You have to have a fairly large gap (one large enough to release gasses without the airlock ever being used) for air to actually circulate, such as a large chip in the jar rim, or a piece of food caught on the rim. This is true of waterlock and one-way valve systems.

Myth: Vinegar is fermented with the cap off, therefore it is an "aerobic" ferment. This is also false.

Fact: Vinegar is initially an aerobic ferment, which creates an alcoholic beverage, after which it moves through the alcoholic phase into a vinegarization phase. The second phase REQUIRES aerobic processes, to develop acetic acid, but only the surface of the vinegar is exposed to the air. Now... if air only moves through the top few inches of liquid (and that is on a curve - less and less with greater depth), then only the top portion is in any way aerobic, and that very little because oxygen simply cannot move well through water. This is science folks - the same science that the water lock people are saying prevents it from being "anaerobic". Of course, their "science" does not include variances for things like density and salt in the water, which both dramatically reduce air movement through liquid (and even cider is more dense than water). That said... ONLY the top few inches are in any way "aerobic", and not enough so to allow the proliferation in any great amount of microbes that will significantly alter the lactic acid production in the container. Apple cider vinegar in fact has lactic acid formed by lactobacillus, it just has more acetic acid by the time it is finished. So what is responsible for the distinct vinegariness? Merely the transformation of sugars and alcohol to acid (partially the same things responsible for the vinegary flavor of pickles, though the processes involve more than one kind of acid). Alcohol rises in a liquid. It rises to the top, where aerobic bacteria from the air can work on it near the surface. They facilitate the process, and are in no way harmful. The transformation of hard cider to vinegar takes longer than the original fermentation period - because the aerobic microbes do not survive and proliferate as well, and they can only work at the top of the jar. 

Myth: Foods fermented in an airlock system are anaerobic. Not true.

Fact: Small amounts of oxygen are always present - why do you think manufacturers of airlock systems still insist that you keep the food under the brine? (Because they know that this is what REALLY ensures success.) As soon as you open that lid, your culture has become "contaminated" with opportunistic microbes, and flooded with air. If you stir it, air is incorporated and often trapped in the food. Indeed, WATER ITSELF is not anerobic, and is constantly releasing oxygen molecules as they separate from hydrogen molecules. This has always been true, and is typically NOT a problem, if you don't mess with it during the first few days when the ferment is establishing itself. Salt and acid have more to do with inhibiting the growth of unfriendly microbes than any type of lid. Keep it under the brine, and keep the salt balance right on pickled foods, and it really doesn't matter!

Myth: An anaerobic environment will prevent the growth of mold. This is also false.

Fact: Recent research has shown some strains of mold that will grow in an anaerobic environment (in fermented foods, specifically - verify this by Googling "anaerobic mold"), and which require only the presence of carbon dioxide (plentiful in fermentations). Further, since no ferment EVER stays completely anaerobic, molds will eventually grow if mishandled or if opened repeatedly and exposed to molds (which are in the air). Additionally, the ferment, as a living food, eventually passes through the phases of good microbial growth, and into one of decay at the end of the life of the ferment (in the fridge, it may take 6-24 months to reach that point), and at this stage, MOLD WILL GROW, no matter what kind of container it is in. The goal of "zero mold" is no more practical than for you to try to clean the mold out of the air. It simply cannot and will not ever happen, and does not NEED to, because the majority of mold is not harmful, and will not proliferate to any great extent in your fermentations anyway, if you treat them right.


The greatest affect on fermented foods has NEVER been the kind of lid you put on it. It has ALWAYS been the method you use aside from the lid!

It does not even have to do with sanitation - ferments done under VERY unsanitary conditions have been shown to not have proliferations of harmful microbes - because the salt inhibits their growth, or the cultures that are being grown simply grow too fast and overpower the opportunistic bad guys (kefir and yogurt are examples).

A maker of sourdough says that if you keep the environment in the jar right - properly fed and cared for (food it likes, temperature it likes) - the sourdough stays happy and grows the right things. If you neglect it or toss in stuff that it does not like, it quickly gets "sick" - because the wrong things are encouraged to grow. This is true (based on scientific principals which I do not have time to break down here), and it is true regardless of the kind of lid - traditionally sourdough was kept in a lidded pot, wrapped in oilcloth, or kept in a jar with a cloth over the top. It was open to airborne microbes all the time, but the care of it is what kept it healthy.

This is true of all fermenting - how diligent you are about feeding your kefir, how diligent you are about NOT messing around with your pickles during the first few days, and how well you attend to the rule of sufficient salt, and keeping foods UNDER the brine, have FAR more effect on fermentation than the kind of lid you are using.

When the conditions in the food itself are correct, the bacteria and yeasts that you want proliferate faster than the unwanted microorganisms, and they then create an environment in which the harmful microbes cannot thrive. Some WILL survive - just as you are breathing good and bad microbes every day, there will always be good and bad ones in your food. Bad ones only cause harm when they completely take over. Even with properly fermented foods, that WILL eventually happen, unless you sterilize the food (killing the good stuff).

Fermented foods are Living Foods. As such, they need to be fed to keep living. You don't feed pickles, so eventually the good microbes run out of food, and die off. Nasty beasties gradually move in after that - they eat the leftovers. If this did not happen, your food would be dead food, not living food. Keeping a lid on the jar, and keeping it under the brine will help to slow down the deterioration processes, but it will not stop it. Eventually the good guys will run out of food and die, and once that happens, the food will degrade.

If anyone tells you that you have to have a certain piece of contemporary equipment to ferment foods successfully, then they either have something to gain, or they don't understand the science as well as they think they do. It isn't as simple as declaring that you need this kind of environment and this little gadget can guarantee it. They are focusing on minutia, and ignoring the more critical elements, which are the things that have allowed fermenting to become a tradition through thousands of years, BEFORE they had that nifty new (and expensive) gadget.

Can an airlock help you ferment more successfully? Maybe - in certain circumstances, for certain climates, and certain personalities.

Is it necessary? No.

Unequivocally NO.

What it is, is CONVENIENT. It keeps you from having to vent the containers or risk a messy encounter with built-up gas. It is EASY. Because you don't have to worry about a potential explosion, or the cat trampling on it, or fruit flies getting into it. So let's be honest about what we are selling! We aren't selling "science", we are selling CONVENIENCE.

You be the one to choose. If an airlock system helps you ferment foods more predictably, great. But if you are trying to get started and need to make do, go right ahead, and know that you aren't doing it "second best" and you aren't taking risky shortcuts. You are just using sound scientific principles to preserve food, just as your ancestors did.

CopyCat Notice



The ORIGINAL one-way valve fermenting airlock! Imitation IS the sincerest form of flattery, and we have noticed that our product has been copied by other sellers of fermenting products. Remember, if you see someone else selling a one-way valve airlock for fermenting, THEY copied US, not the other way around! Fermenta Lock is still the only original invention, handmade in the US. If it isn't orange, it isn't the original!

We invented Fermenta Lock, Fermenta Free, and the valve used for Fermenta Fido and other Fermenta Airlock products. We invented Fermenta Dunk Extender. Patents are prohibitively expensive, and designed by the government not to protect the rights of individuals, but to provide another source of revenue and control for the government and lawyers. We are good at what we do. We have endless ideas and endless creativity, and competition does not scare us. Impatient thieves do not scare us - they are too busy taking shortcuts to make a success of it anyway, and they won't want to take the effort to actually MAKE a product and fill orders.


So if you want to copy our idea, go right ahead. If you want to market and sell a competing product, you are welcome to do so, as long as you do not patent our idea - we had it first, and our posts on FaceBook announcing the invention and launch of it will prove that. This idea is officially in the public domain, placed there by us. We will NOT release supply sources, or part names unless you want to buy them - we'll be happy to sell you an instruction kit. If you buy our product, or look at the images and figure it out for yourself, good on you. Compete with us if you like, just don't screw us, and we'll get along just fine. Big companies who might want to screw us may have more money, and more lawyers than we do, but we have more to gain by suing the pants off a big company, and believe me, we will be well motivated to do so if anyone patents our idea and claims it as their own - this is a free idea. Everybody now owns it.

Published June 23, 2012



Wholesale, Export, and Manufacture of this product by other companies is an option. International distributorships are available for those wishing to export. Please email us to inquire about access to our wholesale website, or in regards to manufacturing any of our products.


Business Building Services Are Available - If you are wanting to build a business like this, where you make things in the home and sell them direct to the customer, or if you want to build a business that you can sell to other people as a complete business package, Firelight Heritage Farm is now offering Cottage Industry Services to aid small business owners in building a successful product or service business from the home. Don't know what you want to do? We can help you figure that out too (something original, and just yours, not a canned business). You get the wisdom and uniquely successful perspective and experience of people who have been business, marketing, and website professionals for more than a dozen years. For more information, visit Why copy someone else's business when you can do something uniquely you and enjoy it so much more?



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Customer Comments

"Living down in Guatemala, we have quite a lot of dampness in our houses and mold is an ongoing battle. After a long dose of antibiotics due to a parasite, I absolutely required probiotics to get my gut back in order and I know homemade sauerkraut has more probiotic content than anything else I could find here. I wasn't able to make my beloved sauerkraut or even Kombucha in my kitchen because mold would start growing immediately on the top. Your Fermenta Locks have literally been a lifesaver for me! No more mold, and PERFECT Kraut EVERY time!!! Thank you for creating such a wonderful product!!!"

A. Kratzert


"Oh how I wish I had found you first!! Too many experts and too many bucks later I discovered your "Lock" and the sheer elegance and simplicity of your system.Thank you for your help and affordability, it makes healthy food attainable."



"I came back to order more FermentaCaps, this time the Fermenta Free version. A wonderful innovation on an already great idea. I have not lost a single batch of sauerkraut since I started using the original Fermenta Locks."



(Last names omitted to protect customer privacy.)


Fermenting is a science, and a bit of an art. It requires care in a few specific things, but doing it right is not particularly complicated. We provide instructions that are accurate to the best of our knowledge, and which are based on the methods we successfully practice ourselves. There are no guarantees of success or safety with fermented foods. While properly fermented foods are not only safe, but healthy to eat, it is up to you to follow instructions to ensure safety, and to trust your eyes and nose, and don't eat things that do not look or smell like food. We offer no guarantees of success with our product. We do warrant that it is as described, and will do what we say it will, but how you use it is your choice.


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