Mould is one of those gross things you’re bound to encounter in your early days of fermenting. I’ve had my fair share and, through trial and error, found what works in keeping mould at bay when I’m fermenting.

When it comes to avoiding mould in your veggie ferments, the most effective thing you can do is to keep your vegetables completely submerged in the brine. Sounds like an easy thing to do, but with veggies that float no matter their size, small floaties of chopped cabbage, and the CO2 buildup that naturally pushes your veg to the surface no matter how tightly it was originally packed, keeping the contents of your ferment completely submerged isn’t always as straightforward as it sounds.

And that’s why you need to think about a weight for your ferment. Contrary to what some big names will tell you though, you don’t need special equipment.

Choosing a fermentation weight

You can get as creative as you like when it comes to choosing a weight, but it’s important to keep a few things in mind.

Make sure whatever you’re using is very clean*, isn’t going to break apart or leak any chemical coatings into your ferment. You don’t want to choose cheap plastic, for example, and metal isn’t a good idea either.

It’s also a good idea to use something that will either cover the entire surface of the ferment or put something underneath your weight that will. I almost always use a stiff outer cabbage leaf for this.

* The best way get your weights sparkling clean is to scrub them with vinegar and then sterilise them with boiling water. Do this with any glass, stone or clay weights you plan to use.

My favourite no-risk, no-fuss fermentation weight

Hands down, a small glass jar is my pick. It’s glass, so there’s no plastic in my ferment (which I find icky and kind of uncertain), it’s easy to clean, it’s heavy, I can fill it with water if I need extra weight and it’s always ready to go.

Using a glass jar as a fermentation weight

To do this, all you need is a jar that’s slightly smaller than the opening of your bigger jar, a cabbage leaf or similar (as per above), and a lid for your bigger jar. You can loosely fit the lid on your bigger jar so that it holds down the smaller jar holding down your ferment.

If you don’t have a lid for your jar, you can always turn the smaller jar right-side-up and fill it with water. The weight of the water will weigh the smaller jar down and work just as well.

See? Completely under the brine!
See? Completely under the brine!

5 popular fermentation weights for you to try

If you don’t like the sound of my jar in a jar solution, you could give one of these popular fermentation weight solutions a try:

  • Sterile zip-lock bag, filled with brine – Filling your zip lock bag with brine gives it the weight it needs to weigh down your ferment. What I love about this is that the bag spreads to cover the surface of your ferment, keeping absolutely everything under the brine. As I mentioned above, though, I don’t like putting plastic in my ferments. Note: you absolutely must use brine in your bag, not plain water. If the bag breaks and it’s filled with water, the water will leak into your ferment and dilute the brine, making your ferment susceptible to the growth of bad bacteria.
  • Boiled stones – If you’re lucky enough to live near, say, a river, you might like to hunt for a stone to use as a weight next time you’re fermenting some veggies or herbs. You’ll want one that’s quite heavy and the right size for your jar. Make sure you boil the stone in water for 15-20 minutes before using it, to get rid of any icky stuff.
  • Trimmed carrot – I haven’t tried this method, and I’m not sure what I think of it. I’ll have to try it and report back. To use this, simply use a cabbage leaf to seal the top of your ferment and use a carrot (that’s trimmed to the right size) to push down the cabbage leaf, with the help of a lid on top.
  • Store-bought fermentation weights – You could try one of the many fermentation weights available to purchase online. The majority of these are made from food-grade ceramic and much easier to use than the solutions above. They come in a few standard sizes, which is a bit of a pain if you tend to use different jars, though.
  • Pot watchers – A pot watcher is a ceramic or glass disc that you can put in your saucepan while you’re waiting for it to boil. The idea is that when the pot starts to boil, you’ll hear it jiggling and/or hear it hit the lid of the saucepan before the water has a chance to overflow. These are obviously food-grade products and provided they’re the right size, they’re perfect to use as a weight for your ferments.

There you have it. My favourite fermentation weight and five extras you can try at home. Some I’ve tried, some I haven’t. It’s a matter of working out what you’re most comfortable with. If you give one of these a try, I’d love to hear what you thought of it.