If you're going to make sauerkraut, you probably want to make a lot, and most recipes I've read suggest that you start with about 25 pounds of cabbage. That sounds like a huge amount, but it's only about five large, solid heads of cabbage and makes about 6 quarts or 12 pints of finished kraut.
The bigger problem is where to store this massive amount of cabbage while it's fermenting.
Fermenting the Cabbage
For 25 pounds of cabbage, you'll need one cup of pickling salt.
Have the crock clean and ready to go. I found it easiest to use a large bowl set on a scale to weigh the kraut as I went, and to mix in the salt. I shredded cabbage until I had 5 pounds in the bowl then mixed that with 3 tablespoons of the salt. I let it sit for about 15 minutes (while I shredded the next batch of cabbage) until it started getting wilty and wet.
At that point, the cabbage went into the crock and I arranged it evenly then pushed down on it until the water rose above the cabbage. Then the next batch of 5 pounds of cabbage went into the bowl with another 3 tablespoons of salt, and I mixed that up and waited until it got wilty. Once more, I dumped it into the crock, arranged it, and pushed down on it until the water rose above the level of the cabbage again. With each layer, the water rose higher because lower levels were still releasing water.
When all 25 pounds had been treated this way, I sprinkled the last of the salt on top, gave it another good squish down, and put a plate on top and weighted that down with a jar filled with water. The idea is that you want to keep the cabbage submerged below the level of the water, but you don't want to compress it so much that gas can't work its way out.
You want to keep the cabbage under about 2 inches of water thoughout the fermentation period. That way, as you're skimming the top, you're not losing cabbage in the process. You might need to add extra brine at the beginning or during the process to maintain that level. To make the brine, heat 4 cups of water and add 1 1/2 tablespoons of canning salt and stir until its combined, then let it cool to room temp before adding it to the cabbage mixture.
I found that at the beginning of fermentation, the brine increased for a while as the cabbage let off more water, then it started decreasing as it evaporated.
Keep the crock covered with a clean heavy kitchen towel all during the fermentation. Check it every day and skim off any foam or scum that forms on the top and add brine, if needed. When the bubbling stops, it's done fermenting, but the time that takes depends on a lot of factors including the temperature and the cabbage.
You can taste the cabbage as it progresses. At first, it will just be briny, and then it will begin to sour. After 2 weeks, it appeared that my saurkraut had finished bubbling, but it didn't seem done yet based on the taste. I poked a skewer down into the cabbage and saw that there were still plenty of bubbles forming, but the cabbage was packed a little too tight for them to be released. I've also read that there are actually two fermentation periods, and the second is less bubbly, but that's when the cabbage becomes more sour.
After another two weeks, the kraut was tasty, really done bubbling, and ready to go into jars. Some people leave the cabbage for many weeks longer after it has finished bubbling so it becomes even more sour, but I was happy with it after four weeks.
Back in the old days, people would leave kraut in a barrel in a cold basement all winter, but it makes a lot more sense now to can it when its at its peak and free up the counter space.
You can choose a hot pack or a raw pack method. The difference between the two is whether the kraut goes into the jars hot or cold, and the processing time. Since it's coming out of a crock at room temp and it's easy to work with that way, the raw pack made the most sense to me.
Raw Pack Canning
You'll also get a rack that fits in the bottom of the pot that holds the jars upright and keeps them from bashing into each other while they're in the boiling water. If you don't have a canner, you can buy a canning rack separately or use a cake cooling rack, if you have a large enough pot. Not only does the rack have to fit, but the jars need to be well underwater during processing, so it's got to be tall if you're using quart jars.
Instructions on jar and lit preparation, general canning instructions, and high altitude adjustments are in the previous post, Water Bath Canning.
Pack the kraut into jars - not mashed tight into the jar, be gentle. If you pack too tight, the kraut will untangle and loosen itself during the canning, then it will rise up and the water level will go lower, and then you won't have liquid covering the kraut when it's done.
Make sure the liquid covers the kraut completely and leave 1/2 inch of air space (headspace) at the top of the jar. Remove any air bubbles and adjust the headspace by adding more liquid, if necessary.
Clean the jar rim and threads, place the lid on, center it, and put the ring on. Tighten the ring. You want it finger-tight only. The point is to allow air out during the boiling so that when it cools, you'll get a vacuum seal. Put the jars into the canner and make sure they're well covered with water.
Bring the water in the canner to a rolling boil and cover the canner during processing. Pint jars should be processed for 20 minutes, and quart jars should be processed for 25 minutes at sea level.
Remove the lid from the canner, turn off the heat, and let the jars rest for 5 minutes in the hot water. Remove the jars and place them upright on a towel and leave them undisturbed for 24 hours to cool completely and to allow the seal to form. You don't need to dry the jars or fiddle with them; just let them dry and cool. Cover them with a towel if it's drafty, but otherwise, just leave them be.
Any jars that haven't sealed completely should be refrigerated and used soon, or remove the lid and start over with a new lid and reprocess it.
Store the sealed jars in a cool place. You can replace the screw bands, loosely, but don't tighten them or you could break the seal. Use the kraut within a year for best quality.