Choosing the right kombucha bottles + caps
Second fermentation is where the fizz is at! And here, you’ll
learn about my favorite kinds of bottles to use for building
You can use these markers to jump down to any of the
sections below, or you can just keep scrolling:
But before we get started, just a quick refresher on the two phases of kombucha fermentation:
1st fermentation (F1) is when your sweet tea ferments and is transformed into kombucha by the starter culture and a SCOBY. At the end of first fermentation, you’ll have unflavored, largely un-carbonated kombucha. Go here to learn more about the F1 process and here to learn about the best type of vessel to use for F1.
2nd fermentation (F2) is when you flavor your kombucha and bottle it for around 3-4 days at room temperature to create carbonation. So below, we’ll walk through different containers you can use for F2.
What to look for...
For F2, you want good-quality, food-grade glass that’s thick enough to handle high pressure contents. And equally important is the cap. You want a cap that can be secured tightly enough to make an airtight seal. That’s what’ll allow you to trap the carbonation into the liquid as your brew ferments in the bottle.
What to avoid…
Poor quality or thin glass can actually be dangerous for F2 if the pressure in the bottle builds up too much. You should also avoid square-shaped bottles since those are more prone to explosions. I really want to stress the importance of using good-quality bottles and caps for second fermentation. You’re brewing a carbonated beverage and it’s a living thing, so it can be difficult to achieve perfect consistency every single time. If you use thin glass or poor-quality glass, you could have a mess on your hands if the carbonation builds and the glass can’t handle it.
Keeping your F2 bottles in a closed cabinet or cooler (without ice) will prevent glass from shattering everywhere and contain the liquid mess if something does happen to go wrong. But you should still steer clear of:
Decorative, colored glass that’s not meant to hold liquids
Flip-top bottles from IKEA
Square bottles (the shape doesn’t lend itself well to handling pressure and makes it more prone to explosions)
Recycled beer bottles (see more details below for exceptions and best practices on these)
Great option: Flip-top bottles (also informally called Grolsch bottles)
These* are really common with a lot of home brewers, and with good reason! They’re some of the
best bottles you can use for F2. The caps make a really airtight seal. There aren’t a ton of
downsides with these bottles aside from the fact that they’re a little pricey per piece. The flip-tops
can also be a bit difficult to open at first (especially if you have joint pain issues), but it gets
easier as you "break them in" over time. You can even get them with ceramic tops (which have a nicer
feel than the plastic-topped ones I link above, but I don't notice a difference in quality). Or get
32-oz/liter ones if you want larger bottles.
Great option: Recycled store-bought kombucha bottles (GT, Health-Ade, etc.)
I’ve only ever recycled GT Synergy, Health-Ade and Kevita bottles, but those are fantastic
to re-use for F2. The caps are really what you want to pay attention to with these, since
those are crucial to holding in carbonation. Make sure you do not remove any of the
paper/plastic liners on the inner portion of the cap. Those help keep carbonation in the
bottle. Use rubber grippers to help you seal them up tight!
Tips on removing labels from recycled store-bought bottles
If you lose your caps, read my section on caps below to find out what types of caps are compatible with these bottles.
Great option: Specialty bottles (Stout, Boston Round, Ring-Neck, etc.)
Since I brew a lot of kombucha, these are my favorite bottles to use. They give me the most
choice in terms of shape and size (there are a variety of sizes ranging from 8, 12, 16 oz. and
more). They’re less bulky than flip-top bottles. And they were the cheapest option, since I
bought them in bulk from a wholesale bottle distributor near me.
Caps are crucial here, read my section on caps below!
I’ve started to see kombucha brewer supply shops selling these online. They mark them
up significantly. So, buy in bulk yourself if you can. A lot of online wholesale bottle stores sell
these at a really low price, but just be aware that shipping costs are generally very high (because
they’re shipping you glass, which is obviously very breakable). If you can find a local wholesale bottle distributor near you that sells directly to the consumer, that’s your best bet. That way, you can look at the bottles yourself, pick up some samples to test before you buy them, and then pick up your order in person to save on shipping costs.
Please note that I have not tested this brand/seller myself (since I bought from a bottle supplier at a discount), so your experience may be different from mine. I also don't know if the caps these come with are the F217 caps I recommend below. That's why I highly recommend finding a supplier in your area. It may save you money too! But I understand if that's not an option. If you don't get a tight seal/good carbonation with using those bottles, you may want to purchase some replacement 38/400 F217 caps here. (Again, these aren't the exact brand I own so you'll need to test them out yourself to see if they work well. If they don't, I'm sorry! Please shoot me an email at firstname.lastname@example.org so I don't recommend them to others!)
Bottle caps are super important!
You want a good cap to ensure that your bottles aren’t leaking carbon dioxide out of your
brews. You want them to trap all that fizzy goodness in your drink! These are the two types
of caps that suit the majority of the specialty bottles I use and work well as replacement caps
for store-bought kombucha bottles.
Polycone Seal Caps
These have a conical liner on the inside of the cap. Lots of sites will tell you that these
supposedly make a tighter seal and hold carbonation in the best. I’ve tested these out against the
basic F217 caps (below) and I haven’t found a significant difference. However, these are oftentimes
much more expensive than the basic caps below, so I don’t purchase these. The price difference hasn’t been worth it for me when the F217 caps have worked.
These look like plain, (usually black) basic caps. If you look at the underside, you may barely notice that there's a liner there, aside from the fact that it’ll probably be a different color than your cap. These liners are generally white. The “F217” part is the name of the liner itself, made of a thin foam core sandwiched between layers of plastic (polyethylene).
These are my favorite caps because they’re the cheapest and work fantastically to keep carbonation in as long as you seal them tight (rubber grippers help!). Plus another benefit of these caps is that once your bottles are well-carbonated, you’ll notice that the caps will be slightly convex or curve upward away from the bottle. This is a great indicator that your bottles have great carbonation and are ready to refrigerate! They flatten out again once the caps are off, and you can re-use them many, many times.
Common cap sizes
Both polycone and F217s come in a variety of sizes. When looking up cap sizes,
the first number refers to the millimeters across in diameter. The second
number refers to the thread on the inside of the cap, which indicates what type
of bottle “screw” works for it.
28/400: Fits Boston Round and Health-Ade bottles.
38/400: Fits Stout, Ring-Neck, GT (Synergy) and Kevita bottles.
Iffy option: Beer bottles
I did a lot of experimenting with bottling my kombucha in beer bottles and capping them with crown caps and a bottle capper. I really wanted it to work out because beer bottles are so cheap and easy to come by! But I did have a bottle break on me. So I will say that you can use them at your own risk and only in specific situations.
For instance, not all brewers want their kombucha carbonated. If you want to flavor or bottle your
kombucha without going through a second-fermentation (so you’re not building up carbonation),
then you can use beer bottles but move them immediately to the fridge.
I’d only be comfortable with leaving kombucha in a beer bottle at room temp for a day at most
before moving to the fridge. Any longer than that, and I’d say you could put yourself at risk for a
Iffy option: Mason jars
I really wanted to like mason jars, but I haven’t been able to produce consistently fizzy results in them. I’ve had too many instances of flat kombucha from mason jars, so I can’t recommend them. Even if I heat the seals up and make them as airtight as possible, mason jars are way more inconsistent than any other F2 bottle I’ve tried.
Dark vs. clear glass
It doesn’t matter much if you use dark or clear glass. If you keep your second fermenting bottles somewhere in direct sunlight, the sun may have some anti-microbial effects that could slow down/halt your fermentation. So people who do that may want to opt for dark glass just to be safe.
But I personally keep all my second ferments in a dark cabinet while they build up carbonation, then they go straight into the fridge, so they barely ever see the light of day until I’m drinking them. Because of that, I prefer clear glass because it allows me to see the flavors easily and it makes it easier to see how bubbly/aggressive the carbonation will be as I open each bottle. (Note: I know I recommend that you don’t keep your F1 vessels in cabinets. But cabinets are OK for F2 because your bottles are already sealed. So there’s no risk for mold contamination from its environment!)
*On this page, you’ll find some affiliate links to sources where I’ve purchased my ingredients/materials that I use. I may get a small cut of Amazon's profit for finding + recommending them to you. It won't cost you any more than you’d normally pay for them. I went through a lot of trial and error to find low-cost, high-quality options to save us all money. But feel free to purchase from wherever you like!