Keep cabbage 1 to 2 inches under brine while fermenting. After adding prepared cabbage and brine, insert a suitably sized glass dinner plate or glass pie plate inside the fermentation container. The plate must be slightly smaller than the container opening, yet large enough to cover most of the shredded cabbage or cucumbers. To keep the plate under the brine, weight it down with two to three sealed quart jars filled with water. Covering the container opening with a clean, heavy bath towel helps prevent contamination from insects and molds while the cabbage is fermenting. Fine-quality fermented vegetables also are obtained when the plate is weighted down with a very large clean, plastic bag filled with 3 quarts of water containing 4½ tablespoons of salt. Be sure to seal the plastic bag.
Note: If you weight the cabbage down with a brine-filled bag, do not disturb the crock until normal fermentation is completed (when bubbling ceases). If you use jars as weight, check the sauerkraut two to three times each week and remove scum if it forms.
If juice does not cover the cabbage, add boiled and cooled brine (1½ tablespoons of salt per quart of water). Add the plate and weights; cover the container with a clean bath towel. Store the fermentation container at 70 to 75 F while fermenting. At temperatures between 70 and 75 F, sauerkraut will be fully fermented in about three to four weeks; at 60 to 65 F, fermentation may take five to six weeks. At temperatures lower than 60 F, sauerkraut may not ferment. Above 75 F, sauerkraut may become soft.
Note: If the fermentations conditions are not right, sauerkraut can spoil. Finished sauerkraut should have a firm texture, and the brine should not be cloudy. If you smell a bad odor, see mold or note a slimy texture, do not taste.
When making additional batches, wash the fermentation container, plate and jars in hot, sudsy water and rinse well with very hot water before use.