Kimchee (also spelled Kimchi) is traditional Korean spiced fermented Napa cabbage, famous for being a great probiotic food and for being one of the cornerstones of Korean cuisine. There are other Kimchee instructables out there, but several things set this particular one apart:
Did you know that foods do not decompose without biological intervention? The food may oxidize or dry out or go stale (starch retrogradation), and some substances may be unstable and break down into a more stable form, but if you took food, sealed it in a totally sterile bell jar filled with an inert gas, and irradiated all the microbes to death, it would never rot. It would sit there like the 14 year old McDonald's burger, forever untouched by decomposition as we know it. This is because decomposition is not merely oxidation and dehydration; decomposition is carried out by decomposers—yeasts, bacteria, molds, worms, insects, or the digestion of some creature. The microbes that would gladly eat your food for you are everywhere; their spores are in the air, and they are often symbiotic with the produce that we buy, naturally occurring on the surfaces of the leaves and fruit. In the days before refrigeration, the options that we had for preserving food were fairly limited, and broadly speaking, they fall into several categories:
Fermentation is best described as human intervention into a three way microbial war for the purpose of preserving food and enhancing its flavor. These are the three major combatants in this microbial war:
These three battle for supremacy over who gets to take over our food, and in the course of doing so, produce substances which fend off the colonization and growth of the others, particularly the decomposers. This microbial chemical warfare is memorably summarized by the observation that one form of filth kills another form of filth.  What we do when we ferment is to make alliances with the microbe of our choice by creating conditions favorable to that particular kind of microbe so that they can take over our food; in exchange for letting them utilize some of the calories in the food, we utilize their natural defenses to ward off unwanted microbes that would decompose the food or cause food poisoning.
In some forms of fermentation, such as Kombucha (fermented tea), we ally ourselves with two classes of microbes at the same time—bacteria and yeast. In others, such as Sake (Japanese rice wine), we switch sides midway through; in sake, mold is used to break down rice starch into fermentable sugars; then, the alliance with mold is broken as the moldy rice is mashed up to break up the mold structures; the mash subsequently liquefied and fermented with yeast, which convert the sugars into alcohol. For vinegar, yet another stage of fermentation is carried out where acetobacter bacteria are employed to convert alcohol (in low enough concentration that it won't kill bacteria) into acetic acid. In the case of rice wine vinegar, all three of the microbes are employed one after another. Many cured meats such as salami and cheeses such as brie are cured with penicillium mold, which colonize their outer surfaces and prevent the infiltration of harmful bacteria. Miso (fermented soy bean paste) is fermented with koji mold and preserved with salt. Sour cream and yogurt are fermented with various kinds of lactic acid bacteria and get their characteristic sourness from lactic acid and other flavorful acids.
In the case of kimchee, the fermentation is carried out by yeast and bacteria, with bacteria being the dominant player.
In addition to fending off unwanted decomposers, fermentation has several great side effects, one of which is the enhancement of flavor. Consider what fermentation does to soy beans: soybeans and tofu are pretty bland, and are commonly used only as a substrate for sauces and other flavors, but once fermented, they become the basis of some of the most savory ingredients ever—miso, doenjang (Korean style fermented bean paste), and soy-sauce. Fermentation is also what gives bread and wine and beer their depth of flavor compared to their unfermented ingredients.
Fermentation also has the added benefit of up-converting carbohydrates into vitamins and increasing the nutritional density of many foods. Consider kombucha; the tea and the sugar used to brew kombucha have no nutritional value besides empty calories, but after fermentation, kombucha is a rich source of B vitamins. Cabbage becomes more digestible and also sees its vitamin content increased by the process of being fermented into sauerkraut and kimchee. The microbes that carry out fermentation need these vitamins, but also have the metabolic pathways to make their own from the starches and sugars present in the food, whereas we do not. We merely benefit from them pre-processing the food.
Now that we understand what's going on when we ferment, let's see this optimized method for making kimchee. Get some friends together and have a kimchee making party, and perhaps get some Korean food and a bottle of soju afterwards.
 This is a paraphrase of an observation on the discovery of penicillin from Cracked.com.
(Note: Please see the photos in every step; a lot of them have attached notes.)
Please obtain the following equipment. Be sure to check the photos, which have notes about these.
5 liter fermentation jar
You can obtain these fermentation jars at Korean markets. Make sure you get the one which has a lid with a moat, which serves as the air lock when water is added. The air lock lets carbon dioxide burp out of the jar as the kimchee ferments, but prevents mold spores and airborne bacteria from infiltrating the fermentation vessel. The method used since ancient times has been the moat filled with water, which is simple and effective.
These fermentation jars cost about $10 at the Korean markets in the San Francisco Bay Area, and come in sizes as small as a pint to as large as 20L for about $24. Do you realize how affordable this is? Even the Perfect Pickler™ mason jar fermentation kits (for 1-2 quart jars) costs twice as much. The home brew supply stores don't even sell fermentation vessels at the prices you can get at the Korean markets. I got my fermentation jar at Kukje market. An equivalent stoneware fermentation crock with an air lock moat in which the lid rests (the traditional European design) typically costs between $80 and $200. For the price of the typical European style pickling crock, you can get ten of these jars and fill your pantry with pickled goodies. Besides being far less expensive, there are several reasons why I like the glass fermentation jar better.
The Korean markets also have smaller quart and pint sized fermentation jars with air-locks built in, all for surprisingly low prices. These work just as well for small pickle batches, and don't require as much overhead space as the water trap air lock mason jar conversions. If you are serious about fermenting vegetables, go to the Korean market or housewares store, and buy yourself a trunk-load of these jars. I don't think you'll find a better value anywhere for fermentation jars.
In the photos, you'll see a couple of large stainless steel basins. These are not merely large kitchen prep bowls; the large one is more than double the capacity of the largest bowl could find at the cooking supply store. I got these at the Korean market for $30 and $40 respectively. They have them in stainless steel, aluminum, and plastic. I prefer stainless. I don't know of any other markets that sell large basins like these. These are used for salting the cabbage for kimchee, and perhaps for bathing small children. Get the largest basins you can; I originally only had the smaller of these two basins, and it proved to be too small; I was loosing bits of cabbage from the undersized basin as I tossed the cabbage to distribute the salt.
These are variously known as pressing stones, fermentation stones, or pickling weights. These are not traditionally used in the Korean method for making kimchee; these are from the European pickling tradition. The purpose of these weights is to keep the vegetables under the brine during fermentation, because mold cannot easily grow on liquids, and where it manages to grow on the surface, it can't easily send hyphae (mold roots) into the liquid. Keeping your sauerkraut or kimchee submerged under the brine is the best way to protect it against mold. I really like this optimization, and have adapted this for my kimchee method. If you don't use fermentation weights to keep the kimchee submerged, white mold may form on the bits that are sticking out of the liquid. There may even be some surface mold on the liquid. Do not be alarmed; the white molds that are able to withstand the acidity of the brine are not harmful; they're just not the kind of fermentation we're trying to promote in kimchee. Pick off or skim off any white mold and dispose of it, and carry on. However, if you get green or black or other colored molds, you should probably discard your kimchee and start over.
Fermentation weights come in a couple of styles. There are circular ones that are about 2"-3" in diameter made of glass or stoneware which are intended for weighing down vegetables being fermented in canning jars, and larger half-circle stones which are much heavier, intended for pressing down sauerkraut in a fermenting crock. The large half-circles are the ones you need for this project. I obtained mine from Amazon for about $22. (I later found these for $7 at Williams Sonoma, which was rather surprising. It's not often that you find things at Williams Sonoma that are a fraction of the cost of the same at Amazon.) These fermentation weights are sized for a 5 liter fermentation crock, and fit my inexpensive glass fermentation jar perfectly.
The fermentation weights that will fit your 5 liter jar are likely to be made of unglazed stoneware, and must be sterilized. Because the stoneware is porous, it could harbor unwanted microbes, which could form colonies and get a head start before the beneficial bacteria become thoroughly established enough to ward off competing microbes. To prevent any unwanted microbes from contaminating your kimchee, wash all your jars and bowls and food processor with hot water and dish soap. The fermentation weights, however, ought not be washed with dish soap because they are porous, and may hold onto soap residue that will ruin the flavor of your kimchee. It is sufficient to wash them with water before sterilizing them. I have not found it necessary to do a full sterilization of the jar, its lid, the basin, etc. because these surfaces are not porous.
Steam is superior to boiling for sterilization
I find that for sterilizing things for fermentation, steam is advantageous for the following reasons:
When water vapor condenses on something in the course of steaming, it not only happens at boiling temperature, it also imparts the quantity of energy it took to vaporize the water. Because of this, steam cooks any unwanted microbes to death very rapidly. Five minutes of steaming is more than enough. Leave your fermentation stones to cool with the lid on; by the time you are ready to use them, they will be cool enough to handle.