Air Locks for Mason Jars – My Fermenting will Reach New Heights

We mentioned that we`ll be experimenting by making homemade liqueur (cordial) soon.  We also mentioned we`d share an exciting discovery (at least it was a discovery for us!).

The following applies to fermenting cordial – but also applies to other fermenting including sauerkraut, fermented pickles and kimchi.

Fermentation requires the removal of air from your product.  The process assists us naturally as gasses produced by fermentation are heavier than air – a layer of gas will easily rest on top of your fermentation unless there is a breeze, someone walks by or airflow changes around your jar.

Kaela at Local Kitchen mentioned using a trick you could do with a balloon and gave a link to find air locks in her article on berry cordial.  This sent me on a mission.

I went to a local u-brew store.  They help people make wine and beer.  They also sell air-locks such as this 3-piece unit (the cork doesn`t count as a piece as you can get different sizes for different jars):

Air Locks for Mason Jars   My Fermenting will Reach New Heights

An airlock allows the natural gasses to force air (and excess gas) out without letting air in.  The 3-piece unit is pretty easy to use:

  1. The largest piece is  inserted in the cork (the `straw`is gently pushed in).
  2. Water is poured into the large piece – there`s a fill line which tells you when to stop.  The water is poured in the outside `bowl` which surrounds the straw).
  3. The second largest piece fits inside the bowl and on top of the straw.  It also goes into the water – this is the actual airlock.  Gas will force air out through the straw and it will bubble through the water to escape – but no air can enter because of the seal made by the water.
  4. The small cap then goes on the top to seal everything in

Take a look (there`s no water in it):

Air Locks for Mason Jars   My Fermenting will Reach New Heights

Our excitement has been the discovery (that I believe Kaela was pointing out but I missed) that the large cork that is used for a carboy (large plastic container for brewing beer) fits a regular-mouthed mason jar!

This means that for a whopping $3 we can easily ferment small batches of `things` in jars.

These are the simple pleasures which excite me!


  1. This is exciting stuff. I had three batches of sauerkraut go bad last year, after years of no trouble at all, so will try the small batch airlock approach next fall. Kimchi, here we come.

  2. These airlocks would work for Kombucha too, I guess. I’ve never made it, but I’ve inspired to try by the Dervaes family and their blog.

  3. Great find, guys. I imagine the added benefit is that you can minimize the sauerkraut-house effect by moving the jar outside to take the white cap off, release the gas in the airlock and change the water.

    • The gas escapes the airlock without removing the white cap. The white cap has about 8-10 little pinholes to allow it to escape while preventing big things from falling into the sealing liquid (sometimes water, but vodka works better since nothing grows in it).

    • Beer-brewer says:

      The gas produced by the fermentation is released continuously.

      The airlock only serves to prevent outside air — and oxygen, dust, bacteria, insects, etc — from getting into the fermenter.

  4. Kate @ Snowflake Kitchen says:

    Oh man. I might actually get a green light for sauerkraut again with this method! I was banned from trying it after one big stinky fiasco…

  5. I considered something like this for small batches of cider. As it is I’m brewing a 5 gallon batch of mead right now and I’m very excited about it :)

  6. You could also do a water lock if you can’t find the little air lock do-dad. Basically you’d just put a hose in the rubber cork and then put the other end of the hose in to a second jar filled with enough water to cover the end of the hose a good bit. We do home beer brewing and on the first fermentation we do the water lock with the hose and then during second fermentation we switch to the airlock that you show in your pictures.

  7. I have started a batch of berry hooch on Monday. I’m using the balloon, I really need to head to the brew store. It’s a good thing to check on the hooch and see the balloons (yes 2 bottles!) still up and I can hear the yeast working. What are you going to do with the left over fruit plup? I’m making vinegar with mine. Nothing like 2 great things from one source.

  8. I ran across something about using airlocks for lactofermentation recently as well. It would be a lot safer around here to go that way than using a kitchen towel or such on the jars in our house – none of us are all that graceful, plus we’ve got adventurous and curious cats.

  9. Could you tell me where you found that stopper? This is exactly what I’ve been looking for, but I’ve called around to local homebrew supply shops here in NY and no one is familiar with it. I’d love to order a bunch if I could find a place that sells them.

  10. Joel, What size stopper did you get?

    • Elenor, I eye-balled it and don`t know.. Is there a way to measure these things (my question mark is failing) – I bought it from a very freidnly store though they don`t speack much English and it wasn`t marked that I can tell. Next time I`d bring a snap lid for a gauge. :)

  11. Elanor I believe it’s a size 13,Here is a website I found,scroll to bottom of that link page and you’ll see the sizes.

  12. TIMELY post!! Thank you, i have been looking for an affordable air lock – this fits the bill. The pickl-it system is very nice but rather spendy, i am very happy i found this cause the harvest is coming in HOT now and all my other fermenting crocks are full!

  13. Thank you for the information on your blog! I am new to the fermenting process. I just threw out a failed first batch of sauerkraut. Your method makes more sense. Do you have a recommended source for the air lock system?

    • Sonia, sad to hear.

      We cought these are a brew-your-own beer store (wine places likely have the same) and have found them online through googling – they’re all about the same price and quality soo no specific place stands out… :)

  14. Again– awesome discovery & thank you! I’m new to the fermentation adventure. After exploding several jars during the typical canning process, I discovered fermentation to be an easier– and tastier– process. But, I often am using my gallon and 2 gallon jars for kombucha. I didn’t have much luck using mason jars because of the air-in-the jar situation. This is an amazing find.

    Two tips though for trashmaster46 about the kitchen towels & adventurous housecats. I got myself some floursack cloths (a little thinner than linen, used for breadmaking) and a pack of heavy duty rubber bands. Doubling up the cloth and using rubber bands around the neck of the jar helped keep the fermenting liquids– kombucha, T’ej, ginger bug– in good order. For the fermenting veg, I used a large piece of plastic wrap that I burped once a day. It kept down on the smell and any critter issues.

    Will be trying this method as soon as I can. Thanks again!!


  15. Hi, I was curious, is the jar in the pic you used a quart size jar, that the number 13 lil stopper thing would fit on? I’m making water kefir, and I want to get it fizzy, and make smaller batches of things to experiment with, So I wanted to make sure that the jar in the pic on top is a quart size, because the 13 size cap with the whole seems like the biggest? Also once you ferment reaches the level you want it, you then remove the air lock, and cover with lid and store right? It doesnt need to be stored with the air lock after fermenting right? Thanks much. Did you find any easier solutions for larger size jars, gallon, half gallon ones?

    • Hi David,

      It was a quart jar – any size mason jar will do as long as it isn’t a wide-mouthed one. If I do anything larger, I just use one of our crocks (we have 3 large ones)…

      We take off the airlock after the initial ferment and let them ferment with a lid on before eventually storing them in the fridge to slow the process.

  16. I just wanted to pass on that at Michaels (and probably many other stores) you can buy half gallon and gallon mason jars which fit a wide mouth ring. Does the cork come in a size that will fit a wide mouth jar?

  17. i took a magnifying glass to the pic of the stopper above and it looks like a # 12 to me – i looked around and found that the # 12 stopper top diameter is 2 1/2 inches – the inside diameter of the ball jar that i have is slightly smaller than that so i figure it will work

    i ordered a few stoppers and airlocks from here

  18. ooops – looks like the # 12 bottom diameter is 2 9/16 not 2 1/2 – that is the # 11.5 spec

  19. scratch that previous correction -
    ooops – looks like the # 12 top diameter is 2 9/16 not 2 1/2 – that is the # 11.5 spec – i am falling asleep while typing

  20. i see the problem now – on the first link to stoppers that someone else posted – it shows the top diameter of a # 12 at 2 1/2 but the link that i posted shows it as 2 916 – so anyway – if your jar inside diameter is less than 2 1/2 inches like my ball jar then i think either the # 12 or the # 13 will work – i probably should have gotten a # 13 instead of # 12 – i might see if i can change it before it ships

  21. Beer-brewer says:

    Even easier than trying to find a large enough rubber stopper — I’ve never seen one that large at a brewing supply store — use a plastic canning jar lid (Ball makes them) and drill a hole sized to fit a smaller stopper.

  22. I saw these at a local u-brew when my husband was buying up his beer making supplies, and I have to wonder how toxic this is?
    When my husband puts these stoppers on the top of his brews the liquid is never touching this stopper.
    These stoppers smell. They have quite a strong rubber chemical smell. If I can smell it, I’m inhaling particles of it, which means if my ferment is is completely covered with liquid then the liquid will be absorbing these chemicals.
    Is there not something safer??
    I wonder if they make corks in larger sizes.

    • The soda centre in Scarborough lady told me she was ordering some corks to fit mason jars. They also sell airlocks, plastic lids that will fit gt kombucha sized jars that already have a hole for the airlock to fit into, and all kinds of big glass jugs with corresponding airlock lids

  23. I did a batch of fermented hot sauce lately and it turned out well. But one jar grew mold because the peppers floated above the surface of the brine. It only took 12 hours for a white mold to form. I tried a number of unsuccessful ways to hold the peppers under the surface of the brine.
    Does anyone know where to get fermentation weights or something else that might work in Toronto? I think something that might work would be some kind of food-grade plastic mesh that would pop into a mason jar and fit in the wide part, keeping the veggies below the narrower neck of the mason jar.

    • I’m told that the white stuff is harmless. Lots of folks just skim it off. I think it might be called kahm yeast, but I wouldn’t swear to that.

      There’s a local guy here in East Tennessee that makes fermented hot sauce. You can read up on his technique on the Joy of Cooking website, fwiw.

      As far as weights are concerned, I suspect you could use a bag of marbles.

  24. Amazon has large corks, but I can’t figure out what size to buy. I guess I need to buy the jar first and measure. If anyone knows offhand, I’d be grateful. You can find these yourself if you search the phrase jar cork stoppers.

  25. There are a lot of ways to make airlocks for mason jars, and more than one option for the airlock as well.

    Ball plastic storage lids are easy to drill, and you can usually find a food grade grommet that will fit the resulting hole. TIP: use an xacto knife to bevel the edge of the hole (very gently) to take off the sharp plastic edge.

    Our company manufactures a simple one-way valve airlock that fits in a 1″ hole. It is more costly than the water lock, but requires no maintenance, is a single piece, and does not stick up much off the top of the jar (so you can’t accidentally knock it off). I’ve got a prototype in the making at the moment for a smaller one that will fit in a smaller hole – just have to finish the initial fabrication (time consuming).

  26. Hey Dan,

    We had the same problem and weights that we did find on the internet would have been a small fortune to get into the country. My best advice is to go to ikea and purchase the glass tea light candle holders. I cannot remember exactly how much they were but I am sure it is under $5 for 12. They have worked extremely well for us! Hope this helps!

  27. For anyone in the GTA area I have great success ordering all my pieces through Wine Kitz. I use the franchise in Pickering and the owner is a sweet older man who is very kind and has ordered us all the bung (rubber stopper) sizes without hesitation. We have found that size 11 works for recycled jam and sauce jars which is great!They sell the airlocks as well of course and I have found the prices to be incredibly reasonable especially since he special orders the bungs for us. The bungs range in price but are usually around $3 each and the air lock is around $2.25. I highly reccomend that location but I would hope any other location would be willing to do the same!


  1. [...] 3 days.  I like to crack the seal slightly each day but an airlock is fine (in fact, one of these mason jar airlocks would work great and would eliminate the threat of too much pressure building up).  When I opened one jar the [...]

  2. [...] fermented it with an airlock (that link tells the story) but you could likely get away with a lid though pressure will build up [...]

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