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What can I ferment with what I have?
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It is bubbling like mad

The short answer It's normal

It's normal: it's lactic acid bacteria giving off gas, mostly in the first days and when it's warm. Put a plate underneath, let the gas out and push the vegetables back below the brine.

Reviewed October 26, 2026 · 15 facts, each with its source

A jar of kimchi full of bubbles and foam up to the rim, on a stoneware plate that catches the brine that has run over 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

The brine is fizzing with bubbles, rising and foaming. The vegetables float or poke above the liquid, and the lid may bulge. When you open the jar, it hisses or overflows. It happens mostly in the first days, and a lot with kimchi.

Why it happens

It's lactic acid bacteria: as they turn the sugar in the vegetables into acid, they give off gas. When it's warm, everything goes faster.

The gas is a good sign, as long as the ferment goes on to sour: the pH has to reach 4.6 or lower.

What to do

It's normal: let the gas out

  1. Put a plate or bowl under the jar to catch any overflow.
  2. Let the gas out: open the lid briefly now and then, or use an airlock.
  3. With a clean spoon, push the vegetables back below the brine.
  4. If your kitchen is above 77 °F, find a cooler spot: with more heat it can spoil.

If it also smells rotten or turns slimy, it's no longer a good sign: throw out the whole batch.

Kombucha bottles are a different matter. Sealed, they build up gas and can explode. See "Exploding bottles".

How to keep it from overflowing

You can't avoid the bubbles, and you don't need to. What you can avoid is the mess:

  • Leave room: fill the jar only to the shoulder, with at least 2 inches of headspace. For kimchi, two-thirds full.
  • An airlock, or a lid that isn't fully tightened, so the gas can get out.
  • A weight that keeps the vegetables below the brine.
  • The temperature the recipe calls for.

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

    Lactic acid bacteria turn sugar into acid and release gas, which makes the bubbles

    “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

  2. 2

    Fermenting vegetables are very active and bubbly: they 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

  3. 3

    A valve lets the fermentation gases 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

  4. 4

    Fill the jar only to the shoulder, with at least 2 inches of headspace

    “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

  5. 5

    Kimchi releases gas and fizzes hard: fill the container only two-thirds of the way

    “Fill container about 2/3 of the way full, as fermenting microorganisms will release carbon dioxide (CO2) and create bubbling and fizzing.”

    Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026

  6. 6

    A plate or bowl underneath to catch any overflow

    “Place on plate or in bowl to catch potential overflow.”

    Colorado State University Extension · Understanding and Making Kimchi (2025) · read on October 20, 2026

  7. 7

    Don't overtighten the lid, so the gas can escape

    “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

  8. 8

    Fermentation gas is a good sign, as long as 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 7 claims
  1. 9

    Open the lid now and then to let the gas out

    “periodically “burp” your vessel (i.e. open the lid) to release the gas.”

    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

    Everything 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

  3. 11

    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

  4. 12

    Fermentation takes less time when it's warm and goes more slowly when it's cool

    “generally taking less time at higher temperatures and proceeding more slowly at lower temperatures.”

    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

    Above 77 °F a ferment can spoil

    “fermentation at temperatures higher than 25°C may result in spoilage.”

    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

  6. 14

    If it is 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

  7. 15

    In airtight containers, kombucha builds up gas and can explode if it isn't watched

    “Storing kombucha in airtight containers can cause the accumulation of CO2 (carbonation), potentially leading to an explosion if not regularly monitored.”

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