Headspace is the amount of room between the fermenting food or brine and the rim/lid of the jar or other fermentation vessel. Every vegetable fermented recipe in this book will call for 1 to 2 inches of headspace because as the produce ferments, carbon dioxide is released, producing small bubbles that can cause the fermented food to rise in the jar (or other vessel). It’s important to check on your ferments every day or two to push the ferment back down and keep the brine level over the produce. Proper headspace also lessens the chance of your ferment bubbling over and causing a mess.
