One of the reasons aluminum cookware is so popular is that it is an excellent conductor of heat. Because of this quality, heat spreads quickly and evenly across the bottom, up the sides and across the cover to completely surround the food being cooked. Aluminum frying pans are particularly popular with consumers in that they help sauté and fry foods quickly. Aluminum is a lightweight metal, about one-third the weight of steel, so in the kitchen, it means that a sturdy aluminum pan is also easy to handle. Aluminum is used for both top of stove cookware and bakeware. Aluminum also does not rust.
Aluminum is also the third most abundant element in the earth's crust. In nature, aluminum is always found in combination with other materials. An ore called bauxite is our most common source of the metal. Bauxite contains a greater percentage of aluminum than do other ores, and the metal can be extracted more economically.
Aluminum cookware is manufactured principally by the following methods:
Stamping, Drawing or Cold Forming:In these methods, flat sheets or circles rolled to the desired thickness are placed on a press. The press then forms the sheet metal into the desired shape. Afterward, both inside and outside finishes are applied, and appropriate handles and knobs are attached. The thickness can vary from 1.8 to 5.0mm.
Casting:Molten aluminum is poured into molds specially designed for each different cookware utensil. It can be gravity cast or pressure cast aluminum. Gravity die casting is suitable for small productions and produces a purer substrate with no outgassing issues. Pressure die casting is the most common process. The liquid metal is injected at high speed and high pressure into a metal mould. Both the machine and its dies are very expensive, but it's a much faster process. In this process, special precautions must be taken to avoid too many gas inclusions which causes outgassing during subsequent heat-treatment or welding of the casting product.
These molds allow the thickness of the cookware to be strategically varied in different areas of the pan for maximum cooking efficiency. For instance, the pan bottoms can be made extra thick for superior heat absorption and the pan walls can be slightly tapered to help create circular heat movement up and down the pan. When the aluminum cools, the mold is opened and the cookware is removed. Cast aluminum utensils are often heavier and thicker than stamped utensils. The bodies of all aluminum utensils are made in one piece so that there are no seams or hard-to-clean crevices.
Generally the gauge or thickness of the aluminum utensils is one feature that determines its quality. The heavier the gauge (thickness), the more durable-and more costly-the utensil. For this reason, the intended use of the utensil should be considered when purchasing. Gauge is usually described by a number, the smaller the number the thicker the aluminum. For example, eight (8) gauge aluminum is thick (.125 inch); twenty (20) gauge aluminum is thin (.032 inch).