This happens as the gases are released by Leuconstoc mesenteroides, these gasses push their way up and out and that’s what’s creating the whispers, bubbles and boil overs. These bacterial strains are most active during the first three days of fermentation. After their work is done the bubbles and brine will settle back down into the jar.
- Leave enough headspace in your jar for expansion. When using a flip-top jar you will hear whispers as the gases that accumulate escapes from the jar. It’s safer to loosen an airtight jar lid because it may lead to an explosion or the ferment bubbling over when opening. The carbon dioxide is heavier than the oxygen and will not allow oxygen in when the lid is loosened slightly. If you don’t want to open the lid slightly I would be good to check the lid and release pressure daily.
- Don’t pack the jar higher than the bottom shoulder of the jar leaving at least 20% headspace for expansion. Sugar-rich veggies or fruits is better to ferment leaving more headspace 30-50%
- Keep the jar in a shallow bowl to catch any brine that spills over.