Cooking a container on top of a heat source is a relatively recent advantage in the history of cooking techniques. The functional demands on top-of-the-stove cooking containers are extremely complex. These pots must be fireproof and waterproof. They should transmit heat efficiently and not interact chemically with any food.
Ceramic pottery was the earliest cookware. It was fireproof, and when coated or glazed, became waterproof. But lead-based glazes resulred in the poisoning of entire civiliations. And it was not until the middle of the Bronze Age (2500 B.C.), when metal containers were introduced, that a functional cookware began to develop. Yet we still refer to most of our cooking receptacles as "pots," a reminder of their origin as pottery.
In comparison to ceramic cookware, metal pots and pans are waterproof, fireproof, virtually indestructible, good conductors of heat and easy to manufacture.
Unfortunately, there is no single, perfect material for the manufacture of pots and pans. Different foods require different types of heating. The materials that produce a splendid caserole make a terrible saute pan. There is, however, one essential quality to look for in all cookware and that is good heat conductivity. You want as much heat as possible from the burner to pass through the pot and then to the food. You also want the heat to be spread evenly throughout the bottom of the pot and up as far as possible along its sides. Some metals do this well. Glass, on the other hand, does not. A glass pot carries heat from the burner up to its contents but only through the area that comes in contact with the heat source. A glass pot will not do a good job of spreading or diffusing heat up its walls.
I tested a series of six-quack stock pots, each made of different materials. Each pot was filled with six quarts of water and placed on a controlled heat burner. Each pot was allowed to bring the water to a rolling boil, and the time was noted. The best pot brought the water to boil in 60 percent of the time needed for the slowest pot. The time saved is not very important. What is significant is the 40 percent reduction in the amount of energy needed to do the job. The following is a brief guide to the properties of various materials commonly used in the manufacture of metal cookware.
ALUMINUM: Once thought of as an element so rare that it was preferred to gold and silver, aluminum (and its alloys) is now the most common metal used in professional cookware throughout the United States. It's light in weight, a great asset when you're lifting a 10-quart stock pot filleed with soup. But some types of aluminum will interact with acid foods, affecting the taste and color of the ingredients and discoloring the pot. Tomatoes, wine and alkaline water will all have a negative effect on aluminum cookware.
Manufacturers, however, have been able to overcome this problem to a certain extent by alloying aluminum with various substances, including magensium, nickel, chromium and silicon. Magnalite is a trade name for an aluminum pot containing about 5 percent magnesium. The magnesium reduces the pot's tendency to interact the food while at the same time making the pot extremely hard.
A number of producers are taking commercial quality aluminum pots and putting them through an electrochemical process that produces a protective finish. This exterior protects the pot from the damaging effects of high acid ingredients while protecting the ingredients from the chemical sensitivity of the aluminum. The food doesn't pit the pot, and the pot does not discolor the food. Because this finish is actually an integral part of the pot, the surface is not damaged by stiring and scraping with metal spoons and spatulas. If you season these vessels property before their first use, they will be extremely easy to clean. A well-made pot of this type was originally introduced to the housewares trade about 5 years ago by The Commercial Aluminum Company of Toledo, Ohio, under the trade name Calphalon. In the past year, a number of manufacturers have introduced similar products, and I have had satisfactory results from the Leyse models.
CAST IRON: Cast iron pots absorb heat slowly and evenly. They retain it well and and are excellent conductors. Cast iron, however, is a brittle material and can shatter if dropped on a brick floor or other hard surface. It will also rust on exposure to dampness. A number of doctors have said that there is no need to fear the ingestion of the small amounts of rust that form on cast-iron cookware. They even claim it helps reduce iron deficiencies. A superior cast-iron brand is Wagnerware.
CAST IRON WITH PORCELAIN-ENAMELED COATING: One way of avoiding the chemical interaction of cast-iron cookware with various substances is to coat the metal core with porcelain enamel. Porcelain enamel is virtually a glass surface. It won't interact with foods. It won't stain, pit or rust, and the bright colors are very inviting. They can, however, chip with exposure to extreme heat or cold, with sudden changes of temperature or when banged against a hard surface. The porcelain finsih also has the unfortunate effect of reducing the heat conductivity of the pot. They are not effective as saute pans . . . chicken parts will be almost fully cooked by the time they develop a browned surface.
Next week a discussion of the special qualities of copper, steel and sandwiched and bonded metals, as they are used in pots and pans. CAPTION: Illustration, no caption