STOCKMAKING HAS always fascinated me. Unlike most ingredient lists that require fresh food, the provisions assembled for the making of stock need not be market fresh. It is the more mature vegetables, meats and poultry that go into the process.

Stockmaking is a technique for extracting the juices of various foods and blending them with water. The classic procedure is to place some meat, an onion stuck with cloves, carrot scraps and some spices into a pot, covering the ingredients with cold water. Boil and skim for 15 minutes, then simmer for three hours. The liquid must be kept at a steady simmer during the entire three hours or the flavors will not be retained properly.

For a pot to retain the transmit heat evenly for a great length of time, it should have a thick face made of conductive material. Bones in the pot will sink to the bottom and if they are burned, even slightly, the stock will be ruined.

It is also wise to select a stock pot with a heavy bottom and lighter sides. Remember that a 10-quart stock pot filled with food and water will weigh over 25 pounds. If you can save some weight in the side it helps. That weight makes it important to have a good set of handles. They must be firmly attached, long enough to fit four fingers and far enough from the pot wall to allow fingers to fit full through the space even while using a thick pot holder or glove.

A stock pot must also be tall and narrow. The smaller the surface area of the liquid, the smaller the field for evaporation. The height also concentrates the food in a narrow tower. As the liquid bubbles up, there is a superior concentration of flavors.

I would not select a stock pot constructed of copper with either stainless steel or a tin wash lining. Though either would do an excellent job; sensitivity to heat and great conductivity are not essential requirements for the size of a stock pot. A good bottom is enough. The copper sides are a great expense without compensatory cooking advantages. I would also avoid stock pots of untreated aluminum. They tend to interact with high acid foods, causing pitting of the pot and discoloration of the food.

Stock pots start as small as four quarts and I recently used a 60-quart colossus. The 16-quart model seems to be adequate for most uses in my five-person family. Be realistic about selecting a proper size stock pot. Most stocks will only hold under refrigeration for three days.

There are a number of manufacturers of commercial quality pots that produce stainless steel stock pots with aluminum slabs on the bottom to increase the base's heat sensitivity. Paderno is a fine example. It is not widely available and the 16.5-liter size costs $98.30.

Calphalon, made by the commercial aluminum company, has a stock pot series that ranges from an eight-quart pot retailing for $54 to a 16-quart pot with a price tag of $87.50. Calphalon is a satiny charcoal finish that eliminates the chemical problem of cooking with aluminum. It is an integral part of the metal, not a bonded surface, and will not interact with food. The bottom is thick enough to prevent scorching. The inside corners are rounded for easy cleaning and the handles are rivited to the pot and easily gripped.

Leyson is the name for a Calphalon-like finish used on pots made by Leyse. Their stock pots start at eight and a half quarts priced at $50.25 and go up to 16-quarts for $75.50. The handles are excellent.

Master Chef pots are constructed of an aluminum alloy on the outside, and interior surface of stainless steel with a core of pure aluminum sandwiched in the center. The aluminum core is not just on the bottom, it is part of the entire shell. The nickel-plated steel handles are of a decent size and attached by strong rivets. Their smallest stock pot is five quarts and sells for $44.50. Their largest is 16 quarts and has a suggested retail price of $109.

All three pots, Calphalon, Leyson and Master Chef, have lids that are sold separately. It is essential to have one for a stock pot.

Naturally a stock pot can be used for other dishes. They are perfect for most types of boiling and poaching, from chicken in the pot to soup and pasta.