Quarter, core, and finely shred 15 pounds of firm, green cabbage. Wash and scald a 2-gallon stoneware crock. Mix 1/4 cup of pickling salt into 5 pounds of the cabbage, place it in the crock, and pack it down with a wooden spoon or potato masher; the brine that forms should cover the cabbage. Continue salting, layering, and packing down the cabbage until the crock is filled to within 3 inches of the rim.
Cover with a clean cloth; tuck its edges into the crock. Place a scalded, snugly fitting plate in the crock over the cabbage; weight it down with a water-filled jar so that brine comes up to, not over, the plate. Let the cabbage ferment in a cool place (under 60°F): it will ferment faster at higher temperatures but won’t be as good.
Daily during fermentation, remove scum from the top of the brine, wash or replace the cloth, and adjust the weight to keep the kraut under brine. Ferment 5 to 6 weeks, or until no more bubbles rise to the surface. Store the kraut, weighted down in its crock, in a cool cellar (remove scum and wash the cloth weekly), or can it by the hot-pack method. Bring the kraut to a simmer (180°F), pack it in hot jars, and cover it with brine to within 1/2 inch of the top. Process for 1/2 hour in a boiling-water bath.