Jars and lids
A 1-liter glass jar and a good closure cover almost everything. Which materials work, how full to fill it and the three ways to close it.
5 min read First steps Reviewed October 26, 2026 29 facts, each with its source
The jar: glass, with a wide mouth
For fermenting at home, the most practical choice is a wide-mouth glass jar. Any food-grade container works, glass or BPA-free plastic1, and 1-quart jars with airlock lids are great for small batches2. A jar doesn't protect as well as a big fermentation crock, and you may lose more batches3, but you can see what's going on inside and it fits in the fridge.
Before you use it, look it over: it should be in good repair, with no scratches, chips or cracks4. Plastic works, but it scratches, and bacteria settle into the scratches5. That's why glass lasts longer.
What size
How much fits, and how full to fill it
What fits depends on the method8:
| Method | In a 1-liter (1-quart) jar | How full |
|---|---|---|
| Dry salting (sauerkraut) | About 950 g (2 lb) of vegetables | To the shoulder, with 2 inches (5 cm) free9 |
| Brine (pickles) | About 450 g (1 lb) of vegetables and 2 cups of brine | To the neck10 |
| Kimchi | About 600 g (1.3 lb) | Two-thirds full11 |
No more and no less. With too much air on top, mold or scum forms more easily12; filled to the brim, the ferment bubbles and can overflow13. Stand the jar on a plate for the first few days.
What doesn't work
- Metal. No copper, iron or galvanized metal containers14: metal reacts with acid15. High-grade stainless steel is the exception16.
- Earthenware or ceramics with an unknown glaze. Some glazes don't stand up to acid and can leach heavy metals into the food17, and lead-glazed crocks are out14. If you don't know what the glaze is, don't use it: Fervida doesn't accept any crock that isn't sold as food-safe.
- Plastics that aren't made for food. No hardware-store buckets and no garbage bags18.
Three ways to close it
Fermentation gives off gas, and the container has to let it out or it can burst19. Fervida's recipes let you choose:
| Closure | How it works | What you do | Which recipes |
|---|---|---|---|
| Airlock lid | The lid keeps air out and the valve lets gas out20 | Nothing | All |
| Regular lid | Closed, it doesn't let gas out | Loosen it for a moment at each check21 and close it again right away22 | Sauerkraut and brine |
| Lid not tightened | Gas escapes without loosening it23 | Not so loose that insects or spores get in24 | Kimchi |
| A cloth | No lid: plate, weight and a clean towel on top25, which keeps insects and molds out26 | Check it 2 or 3 times a week and lift off any film27 | Sauerkraut |
The airlock is the easiest: there's nothing to remember. A regular lid works too, as long as you remember to loosen it. The cloth is the old crock method, and it asks for more attention.
If you use a metal lid, keep an eye on it: acid and salt wear it down, which is why plastic lids are recommended28.
Cleaning it
Wash the jar, the lid and the weight in hot soapy water, and rinse them well with very hot water before use29. Do the same after every batch, and check that the lid's gasket and the valve are clean and intact.
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
Food-grade containers, glass or BPA-free plastic
“Use food-grade containers such as glass or plastic (BPA free)”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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2
Quart jars with airlock lids are great for small batches
“Quart-size glass jars with airlock lids are great for small batches”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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3
Jars work, but more batches may be lost than in a crock
“Fermenting sauerkraut in quart and half-gallon Mason jars is an acceptable practice, but may result in more spoilage losses.”
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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4
Food-grade, in good repair, no scratches, chips or cracks
“Containers should be food-grade, in good repair, free of scratches, chips or cracks, and appropriate for acidic conditions.”
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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5
Plastic scratches, and scratches harbor bacteria
“Plastic can be used but is subject to scratching which can harbour bacteria and may leech potential contaminants.”
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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6
Smaller batches fail less
“there is less chance of failure when smaller amounts are made.”
Washington State University Extension, Lewis County · Sauerkraut Making · read on October 26, 2026
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7
A 1-gallon container for every 5 lb of vegetables
“A 1-gallon container is needed for each 5 pounds of fresh vegetables.”
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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8
A quart jar holds about 2 lb dry-salted or 1 lb in brine
“Remember, a 1-quart jar will hold 2 pounds of veggies when dry salting, and 1 pound when adding a brine.”
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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9
Dry-salted, to the shoulder with 2 inches free
“Fill only to the shoulder of the jar, leaving at least 2 inches of head space,”
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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10
With brine, to the neck
“Fill to the neck of the jar if using a brine.”
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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11
Kimchi, to two-thirds
“Fill container about 2/3 of the way full”
Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026
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12
Too much air on top brings mold or scum
“Leaving too much headspace in a jar will allow extra space for oxygen to collect, causing mold or scum to form on the surface.”
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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13
Ferments bubble and can overflow
“Fermented vegetables are quite active and bubbly; they can ooze out of the jar if you are not careful.”
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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14
No copper, iron, galvanized metal or lead-glazed crocks
“Do not use copper, iron, or galvanized metal containers or lead-glazed crocks”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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15
Metal reacts with acid
“Metal containers are not suitable due to their reactivity with acid.”
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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16
High-grade stainless steel can be used
“High-grade, commercial stainless steel can be used”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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17
Some glazes leach heavy metals in acid
“Some pottery glazes are not acid safe and may leach contaminants such as heavy metals into the food if used.”
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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18
Only food-grade plastics: never garbage bags
“Caution: Be certain that foods contact only food-grade plastics. 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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19
The container must let gas out so it doesn't burst
“During the fermentation, containers should allow gas to vent to avoid containers exploding.”
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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20
The lid keeps air out; the valve lets gas out
“A lid prevents oxygen from entering the jar. However, it is important to vent the jar with a one-way valve to release the gases that form during fermentation.”
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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21
Without a valve, loosen the lid now and then
“If a one-way valve is not used, the gases will need to be released manually by loosening the lid occasionally.”
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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22
Open the lid only briefly
“The lid should only be opened briefly to limit oxygen from entering the container.”
University of Minnesota Extension · Preserving food at home: Fermentation (reviewed 2026) · read on October 25, 2026
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23
For kimchi, the lid not tightened so gas escapes
“do not over tighten, to allow the carbon dioxide gases to escape.”
Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026
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24
But not so loose that insects and spores get in
“lids should not be too loose to prevent contamination from insects & mold spores.”
Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026
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25
Plate, weight and a clean towel
“Add plate and weights; cover container with a clean bath towel.”
National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026
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26
The towel keeps insects and molds out
“Covering the container opening with a clean, heavy bath towel helps to prevent contamination from insects and molds while the vegetables are 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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27
With a cloth, check it 2 to 3 times a week
“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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28
Plastic lids are better: metal lids degrade with acid and salt
“Use of plastic jar lids is advisable since metal lids will degrade under acidic and salty conditions.”
University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026
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29
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