Fermentation weights
The weight is what keeps vegetables under the brine, and mold doesn't grow under the brine. What works as a weight and how to choose yours.
5 min read First steps Reviewed October 26, 2026 27 facts, each with its source
What a weight is for
Vegetables float. As soon as a piece pokes above the brine, it can spoil1: mold needs air, and it grows right where the ferment meets the air2. A weight keeps the vegetables submerged3 for the whole ferment.
It matters most at the start. During the first 24 to 48 hours, gas pushes the vegetables up4, and without a weight they end up on top.
How much brine on top
What to use
| Weight | Works in | Keep in mind |
|---|---|---|
| Tempered glass disk7 | Wide-mouth jars | It has to fit through the mouth of the jar |
| Ceramic weight8 | Jars and crocks | Food-safe, with no questionable glaze |
| Bag of brine9 | Any container | Takes the shape of the container and seals the edges10 |
| Plate and water-filled jars11 | Large crocks | The plate almost as wide as the opening. One water-filled jar also works12 |
| Stainless steel spring with a venting lid13 | Small jars | Presses down from the lid |
| Whiskey stones14 | Small jars | Never rocks from the garden |
A whole cabbage leaf laid over the vegetables helps keep small pieces from slipping up around the edges of the weight15.
The brine bag, step by step
It's the cheapest weight and one of the best16. Use a food-grade freezer bag, never a garbage bag17, and ideally two, one inside the other18. Fill it with brine, the same you'd use to top up sauerkraut, about 28 g of salt per liter, and seal it well. It holds brine and not water for a reason: if the bag leaks, what drips into the jar is brine19, so it doesn't dilute the ferment's salt.
With a brine bag, the NCHFP says not to disturb the ferment until the bubbling stops20. If you use jars as weights instead, check it 2 or 3 times a week and skim off any film21.
If the weight isn't enough
You'll see it first at the edges: that's where mold appears when the vegetables aren't held properly under the brine22. If a piece pokes out, push it back down with a clean spoon and keep everything pressed down23. If what's missing is liquid, add a weak brine, about 28 g of salt per liter24, and never plain water, which would dilute the salt. Gas lifting the cabbage in the first few days is normal: just press it down again.
How to choose one
Cleaning it
Wash the weight like the jar: in hot soapy water, then rinse it well with very hot water before use27.
Where every number comes from
Every number in the text leads to its figure: the exact sentence from the official guide it comes from, in its own language.
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1
Vegetables float, poke out and can spoil
“Fermenting vegetables may float to the surface and poke up out of the brine where they may spoil.”
K-State Research and Extension (Kansas State University) · Taking a New Look at Fermented Foods (MF3491, June 2020) · read on October 20, 2026
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2
Mold needs air and grows where the ferment meets the air
“Molds require oxygen to grow. Molds can grow on the surface of the ferment at the air interface.”
UC Davis, Department of Food Science and Technology · Common issues with fermented fruits and vegetables (v1.0, 15-mar-2022) · read on October 20, 2026
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3
Weights keep the vegetables submerged
“Weights can be used to keep the produce submerged.”
UC Davis, Department of Food Science and Technology · Common issues with fermented fruits and vegetables (v1.0, 15-mar-2022) · read on October 20, 2026
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4
In the first 24 to 48 hours, gas pushes the cabbage up
“During initial fermentation (24 to 48 hr), carbon dioxide gas forms and pushes up cabbage, causing heaving.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.2: Sauerkraut (2024) · read on October 26, 2026
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5
1 to 2 inches (2.5–5 cm) under the brine
“Cabbage and cucumbers must be kept 1 to 2 inches under brine while fermenting.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026
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6
At least 3 cm (1.2 inches) of brine above the vegetables
“There should be at least 3 cm or more of liquid brine between the fermented vegetables and the top of the brine.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.1: Fermented Vegetables (August 2024, updated December 2024) · read on October 25, 2026
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7
Tempered glass weights
“Tempered glass weights”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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8
Ceramic weights
“Ceramic weights”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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9
A food-grade bag filled with brine
“Food grade bag filled with brine”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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10
With enough brine, the bag seals the edges of the jar
“You need enough brine to help the bag form a seal around the edges of the jar or container.”
Washington State University Extension, Lewis County · Sauerkraut Making · read on October 26, 2026
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11
A plate with 2 or 3 water-filled jars on top
“To keep the plate under the brine, weight it down with 2 to 3 sealed quart jars filled with water.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026
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12
Or one glass jar of water on the plate
“You can also use a glass jar filled with water to weigh down the plate.”
University of Minnesota Extension · Preserving food at home: Fermentation (reviewed 2026) · read on October 25, 2026
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13
A glass disk or a stainless steel spring with a venting lid
“glass weighted disk, or stainless-steel spring with venting lid for small batches.”
Oregon State University Extension Service · Sauerkraut: Problems and solutions · read on October 26, 2026
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14
Whiskey stones for small jars, never garden rocks
“Whiskey stones are good for smaller vessels (do not confuse with rocks)”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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15
A cabbage leaf helps stop pieces floating up
“A cabbage leaf can help prevent floaters, a brine-filled bag can serve as the weight”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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16
A large sealed bag of brine on the plate
“Fine quality fermented vegetables are also obtained when the plate is weighted down with a very large clean, plastic bag filled with 3 quarts of water containing 4-1/2 tablespoons of salt. Be sure to seal the plastic bag.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026
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17
Never garbage bags
“Do not use garbage bags or trash liners.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026
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18
One food-grade bag inside another
“Put one food-grade plastic bag inside another.”
Washington State University Extension, Lewis County · Sauerkraut Making · read on October 26, 2026
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19
If the bag leaks, what spills is brine
“If the bag leaks, the extra brine will be added to the produce.”
University of Minnesota Extension · Preserving food at home: Fermentation (reviewed 2026) · read on October 25, 2026
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20
With a brine bag, leave the ferment alone until it's done
“If you weigh the cabbage down with a brine-filled bag, do not disturb the crock until normal fermentation is completed (when bubbling ceases).”
National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026
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21
With jars as weights, check it 2 to 3 times a week
“If you use jars as weight, you will have to check the kraut 2 to 3 times each week and remove scum if it forms.”
National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026
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22
Mold shows at the edges when the weight doesn't hold
“mould is clearly visible at the edge of a crock fermentation where plastic has not properly been weighted down over the brine.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.1: Fermented Vegetables (August 2024, updated December 2024) · read on October 25, 2026
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23
Keep it pressed down so air doesn't reach it
“Keep it pressed down to minimize air exposure.”
Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026
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24
Always covered; if short, a weak brine
“Keep the cabbage covered with brine. If necessary, add more weak brine made by dissolving 1½ tablespoons salt in 1 quart water.”
Washington State University Extension, Lewis County · Sauerkraut Making · read on October 26, 2026
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25
Slightly smaller than the opening, but covering most of the vegetables
“The plate must be slightly smaller than the container opening, yet large enough to cover most of the shredded cabbage or cucumbers.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026
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26
Everything food-grade and easy to clean
“All materials should be cleanable and food-grade.”
BC Centre for Disease Control, Environmental Health Services · Safety of Fermented Foods, Section 3.1: Fermented Vegetables (August 2024, updated December 2024) · read on October 25, 2026
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27
Wash in hot soapy water and rinse with very hot water
“The fermentation container, plate, and jars must be washed in hot sudsy water, and rinsed well with very hot water before use.”
National Center for Home Food Preservation (USDA, University of Georgia) · Suitable Containers, Covers, and Weights for Fermenting Food · read on October 26, 2026