While fermenting, the shredded cabbage must be kept below the surface of the brine formed by the salt and liquid from the pounded cabbage. Bubbles will form and must escape. I chose a dinner plate just a little smaller than the diameter of the crock. The small shreds of cabbage you can see above the plate will be removed with a slotted spoon. Tip the plate to one side to make sure no air is trapped under it.