In the kitchen, different metals exhibit different characteristics. Stainless steel is non-reactive--meaning that it does not create unpleasant flavors when cooking acidic foods like tomatoes--but it is a poor conductor of heat. Aluminum and copper are superb heat conductors, but both are reactive to acids. Top cookware lines blend the best features of different metals together in a process called "cladding."
Cladding involves pressing various layers of metals together under pressure to create a sandwich, so each layer's best features can do their jobs. In its simplest form, an aluminum core is sandwiched between two layers of stainless. The stainless interior provides an easy to clean, non-reactive surface for food contact. The stainless exterior is easy to clean and attractive. The aluminum hides in the middle doing the heavy lifting of heat conduction.
Variations on this basic idea have evolved for a number of different purposes. To offer a lower-priced option, some manufacturers produce partially-clad construction rather than fully-clad, limiting the aluminum to the bottom of the pan. "Cook's Illustrated" test kitchen found these to be better than single-component construction, but preferred the performance of fully-clad pans. Among fully-clad designs, manufacturers have ramped up the marketing machines to capture the attention of well-heeled cooks, offering three-ply, five-ply and even seven-ply in a dizzying assortment of metal combinations.
The "Cook's Illustrated" test kitchen found little difference in the cooking performance of any fully-clad design, from a simple two-ply to the very pricey seven-ply. When shopping for fully-clad cookware, the choice between all the available brands comes down to your budget and two other criteria: aesthetics and performance on induction stove tops.
A wide variety of exterior finishes is available, including bright finished stainless, the "stealth bomber" look of anodized aluminum and the "French bistro" look of polished copper, among others. Choose the variation that fits your kitchen design and your budget.
Induction Stove Tops
Induction burners have burst onto the market in recent years. They use an electro-magnetic method that heats the pan, but the stove top itself never gets hot. For pans to work with induction burners, they must contain a layer of magnetic steel--which most stainless steel is not. If you have an induction stove, be sure that your cookware choice is compatible. If not, don't pay for a feature you don't need.