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My jars

The jar is overflowing

The short answer It's normal

It's normal: it's the fermentation gas pushing the brine up. Set a plate underneath, let the gas out, press the vegetables down and check they're still covered.

Reviewed October 26, 2026 · 16 facts, each with its source

A very full jar of kimchi, full of bubbles, whose red brine has overflowed from under the closed lid, run down the glass and pooled on the plate beneath AI

When in doubt, throw it out. Fervida can’t see your jar. No page can tell you something is safe: it can show you how to look.

What you see

Brine creeps up the neck of the jar and spills over the lid or out of the airlock, leaving a sticky puddle around it. When you open the lid, it can rush up all at once, full of bubbles. Sometimes, when it settles again, it leaves the top layer of vegetables out of the liquid.

Why it happens

The bacteria fermenting the vegetables turn their sugars into acid and gas. The gas gets trapped between the vegetables as bubbles, takes up room and pushes the brine upward. If the jar is too full, it has nowhere to go and spills out.

It's a sign the fermentation is alive. Warmth speeds it up: above 77 °F (25 °C), the bacteria grow very fast. Once fermentation is done, the bubbling stops and the jar calms down.

What to do

It's normal: give the gas some room

  1. Set a plate or a bowl under the jar.
  2. If it has a lid without an airlock, open it briefly to let the gas out and close it again right away.
  3. Press the vegetables down with a clean spoon or with the weight so they sit below the brine.
  4. Check that they're still covered. If a lot of liquid has been lost, top up with boiled and cooled brine, with the same proportion of salt as the recipe.
  5. Wipe the rim and the lid.

The gas is only a good sign if everything else is fine. If it smells rotten, feels slimy or has mold, throw it out. If you have strips or a pH meter, check the pH: it must not rise above 4.6. When in doubt, throw it out.

How to prevent it

  • Don't overfill. Dry-salted, like sauerkraut, fill to the shoulder of the jar and leave at least 2 inches of space; in brine, fill to the neck.
  • A one-way valve, or open the lid briefly now and then to let the gas out.
  • A cool spot, within the temperature the recipe calls for. Warmth speeds up the fermentation and makes it rise more.

Where every figure comes from

Every statement on this page comes from a food safety guide. We keep a copy of each source and quote its exact words, in its original language.

  1. 1

    An active ferment is bubbly and can ooze out of the jar

    “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

  2. 2

    Without an airlock, let the gas out by loosening 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

  3. 3

    Dry-salted, fill to the shoulder of the jar and leave at least 2 inches of space

    “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

  4. 4

    In brine, fill to the neck of the jar

    “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

  5. 5

    A one-way valve lets the gas out

    “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

  6. 6

    The bacteria make acid and gas, which bubbles up through the brine

    “Bacteria, such as Lactobacillus spp., convert sugars into lactic acid and release carbon dioxide, which creates bubbles in the liquid or brine.”

    University of Minnesota Extension · Preserving food at home: Fermentation (reviewed 2026) · read on October 25, 2026

  7. 7

    Open the lid only briefly, to let in little air

    “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

  8. 8

    Gas is a good sign only if the pH stays below 4.6

    “Some fermentation microbes make carbon dioxide gas during the fermentation process. This can be a good sign, but only if the pH stays below pH 4.6”

    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

Show the remaining 8 claims
  1. 9

    Every vegetable below the brine

    “All produce should be submerged in the brine liquid.”

    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

  2. 10

    A rotten smell means a failed ferment

    “A putrid smell indicates a failed fermentation.”

    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

  3. 11

    If there is mold anywhere, the whole batch goes

    “If you confirm mold growth on any part of a ferment, it should be immediately discarded.”

    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

  4. 12

    Above 77 °F, the bacteria grow very fast

    “High temperatures >25oC. LAB grows very fast with rapid acid production resulting in poor flavour.”

    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

  5. 13

    If the juice doesn't cover them, add boiled and cooled brine

    “If juice does not cover cabbage, add boiled and cooled brine (1-1/2 tablespoons of salt per quart of water).”

    National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026

  6. 14

    Fermentation is done when the bubbling stops

    “until normal fermentation is completed (when bubbling ceases)”

    National Center for Home Food Preservation (USDA, University of Georgia) · Sauerkraut · read on October 20, 2026

  7. 15

    If it's slimy or smells rotten, throw it out

    “If fermented product is slimy, smells spoiled/rotten, discard it.”

    University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026

  8. 16

    When in doubt, throw it out

    “When in Doubt—Throw it Out”

    University of Illinois Extension · Fermentation handout (2020) · read on October 20, 2026