Cookware Materials
Properties, Care & Use

     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. This is one of the reasons why many leading food manufacturers are packaging convenience and frozen foods in disposable aluminum containers.

     Relatively, aluminum is a lightweight metal, a property that makes it very useful for building aircraft. In the kitchen, it means that a sturdy aluminum pan is also easy to handle, since it is lightweight for its size.

     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 ores, and the metal can be extracted more economically.

     Some people are surprised to learn that they ingest trace amounts of aluminum virtually every day of their lives. It's because aluminum is so abundant in soil that plants naturally absorb it as they grow. Likewise, animals which are raised for food absorb traces of aluminum from their feed.

     The use of aluminum cooking utensils has been subject to notions that it is harmful to health. Aluminum occurs naturally in the human body, on the average, a content of 300mg. FDA studies indicate that the ingestion, if any, aluminum into the body from aluminum cookware is so minute, that there are no adverse health effects.

     A study at the University of Wisconsin determined that only 2.5mg of aluminum per day will be typically added to the diet from this source, if all cooking and food handling is done with aluminum products. It is doubtful that even a portion of this amount becomes biologically available; most, if not all, passes naturally out of the body. There are many other sources of aluminum ingestion far greater than that from aluminum cookware that are equally harmless to the human body, such as over-the counter medications.

Manufacturing

     Aluminum cookware is manufactured principally by the following methods: stamping, drawing and casting.

     Stamping or Drawing: In the stamping and drawing method, flat sheets or circles of metal rolled to the desired thickness are placed on a press. The press then forms the sheet metal into the desired shape.

     Afterward, the finishes are applied, both inside and outside, and appropriate handles and knob attached.

     Casting: Molten aluminum is poured into specially designed molds for each different cookware unit. The molds for casting allow the thickness of the cookware to be strategically varied to those areas of the pan for maximum cooking efficiency.

     For example, the pan bottoms can be made extra thick for superior heat absorption and the panwalls can be slightly tapered to create a circular heat movement up and around the pan. When the aluminum cools, the mold is opened and the cookware removed.

     Cast aluminum utensils tend to be heavier and thicker than stamped. 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 utensil is one feature determines its quality. The heavier the gauge (thickness), the more durable and more costly the utensil. For this reason, the intended use of a utensil should always be considered when purchasing.

     Gauge is usually described by a number, the smaller number, the thicker the aluminum. For example, eight (8) gauge aluminum is thick (. 125 inch); twenty (20) gauge aluminum is thin (.032 inch).

Finishes

     Aluminum utensils are manufactured with a wide variety of finishes. Stamped and drawn utensils may have exterior finishes of polished natural aluminum, chrome plate, anodized (with or without color), porcelain enamel coating, nonstick coatings, or colored organic coatings (acrylics, polyamides, etc.). Usually bottoms have a satin finish or are porcelain enamel coated; both finishes help absorb heat.

     Cast aluminum cookware may have exterior finishes of colored porcelain enamel coating, polished, hammered or velva-glazed natural surfaces, colored organic coating, or hard-coat anodized surfaces. The inside finish on aluminum utensils may be a natural finish, "sunray" or "spun" high polish finish, hard-coat anodized finish or nonstick coating.

Use And Care of Aluminum Cookware

     New aluminum utensils require washing in warm sudsy water to remove manufacturing oils. After use, aluminum utensils, like most cookware, should be allowed to cool before washing or soaking. This is a simple safeguard against warping, as well as preventing accidental bumps in handling. Drying immediately after washing will help preserve their appearance. Wash them each time they are used.

     Undissolved salt allowed to remain on an aluminum surface may cause pitting. Add salt to liquid after it reaches the boiling point and stir to dissolve it completely. Do not allow acid or salty foods to remain in aluminum-finished utensils for long periods of time, because this may cause pitting.

     Because it combines easily with other natural elements, aluminum may stain when it contacts minerals in water and in foods.

     Automatic dishwashing may increase the amount of staining when the high heat of the drying cycle is added to minerals naturally present in water and the chemicals used to purify water. For that reason, hand washing may be preferred to preserve the attractive finish of aluminum utensils.

     Utensils with coated exteriors and interiors may be washed in automatic dishwashers. However, care should be taker when loading them into the dishwasher to avoid marring or scratching the coating.

     To remove food which may have accidentally burned on inside a utensil, fill the pan with water to cover the burned food and simmer over low heat until particles loosen, occasionally scraping burned particles with a wooden spoon. After simmering, scour, wash normally, rinse in hot water and dry.

     Stains and discolorations that may appear on aluminum utensils can be removed by boiling a solution of two to three tablespoons of cream of tartar, lemon juice or vinegar to each quart of water in the utensil for five to ten minutes. Then lightly scour with a soap-filled scouring pad.

     Cooking acid foods such as tomatoes or rhubarb will remove the stains naturally without affecting the cooked food product.

     To remove stains from the aluminum exterior, use nonabrasive cleanser. Cooking tools made of wood, plastic or smooth-edged metal are recommended for use in aluminum utensils. Sharp-edged tools such as knives, mashers and beaters may scratch aluminum.

STAINLESS STEEL COOKWARE

Properties Of Stainless Steel Cookware

     Stainless steel cookware and bakeware is exceptionally durable. Once stainless steel has been stamped, spun, or formed into utensil shape, it takes an extremely hard blow to dent it. Its attractive finish won't corrode or tarnish permanently, and its hard, tough, non-porous surface is resistant to wear. Extremely smooth and scratch resistant, stainless steel utensils take an excellent polish.

     Stainless steel is one of today's most glamorous, versatile and useful metals. It is used virtually everywhere - in space ... on the exteriors of skyscrapers ... throughout industry ... and, just as important, in millions of kitchens where top-of-range cookware, bakeware, pantryware, tools and other equipment ease the work of homemakers.

     Like other steels, stainless steel is an alloy-a combination of iron and other metals. What makes it different from other steels, however, is that it contains at least 11 percent chromium. It is the chromium that makes the steel stainless all the way through.

     Stainless steel may also contain other elements, such as nickel, molybdenum, columbium, or titanium. These materials can contribute special hardness, high temperature resistance, and resistance to scratching and corrosion to the finished stainless steel alloy.

Manufacturing

     Stainless steel bakeware usually is fabricated of solid stainless steel. On the other hand, top-of-range stainless steel utensils are generally made by combining stainless with other metals, usually aluminum, copper or carbon steel. The other metals improve the utensil's heat conductivity.

     Various manufacturing processes are used to combine stainless steel with these other metals. The resulting combinations are described as two-ply, three-ply, bottom clad, three-ply/bottom clad, and five-ply/bottom clad and five-ply.

     Two-ply cookware commonly have stainless steel interiors with another metal on the exterior. In a few instances, this arrangement is reversed, with the stainless steel on the outside.

     Three-ply cookware have stainless steel on both the inside and outside surfaces with a layer of copper, carbon steel, or aluminum forming the core.

     Bottom clad utensils are formed with solid stainless or three-ply, and copper is plated to the bottom or aluminum is applied to the bottom by casting, bonding or metal spraying.

     Five-ply/bottom clad utensils are made by the three-ply process, with two clad layers on the bottom. Five-ply utensils are made with stainless steel on both the inside and outside surfaces with three layers of aluminum or other metals forming the core.

     In the actual manufacture of stainless steel cookware, the metal's versatility permits it to be formed into a wide variety of attractive and functional shapes, limited only by the imagination of the designer or the desires of the consumer.

Finishes

     Appearance is an important consideration in the selection of cooking utensils. A choice of high polish or satin finish is normally available on stainless steel cookware. Either of these attractive finishes blends well with all colors and periods of kitchen décor.

     Also, to meet decorator demand for color in cookware, manufacturers are producing cookware with porcelain enamel exteriors on stainless steel. But the cooking surface is always stainless steel, where case of cleaning and protection of food quality are most important.

Use and Care

     Before using a new stainless steel utensil, check the manufacturer's tags and labels for special tips on use and care. Wash the utensil thoroughly in hot sudsy water to remove manufacturing oils and polishing compounds.

     Stainless steel is one of the easiest materials to clean and keep clean. Washing by hand in hot sudsy water or in a dishwasher usually is the only requirement for keeping stainless utensils bright and shiny. Prompt drying prevents water spots.

     To remove burned-on foods, soak and wash in hot sudsy water. Light scouring with a non-abrasive household cleaner and a nylon scouring pad or a commercial stainless steel cleaner will remove stubborn bums on the interior surfaces.

     High heat may cause a mottled, rainbow-like discoloration commonly called "heat tint". Cooking certain starchy foods-such as rice, potatoes, or peas-may cause a stain on the inside of the pan. Both of these can be removed easily with any one of a number of readily stainless steel cleaners.

     Undissolved salt will "pit" steel surfaces. Add salt to liquid after it reaches the boiling point and stir to dissolve it completely. Do not allow acid or salty foods to remain in stainless steel for long periods of time.

     With normal use, stainless steel cookware will not dent, warp, or chip. It thrives on exposure to air, so it is an attractive utensil to display in the kitchen.

COPPER COOKWARE

Properties Of Copper Cookware

     Copper, alone or in an alloyed form, has been used in cooking utensils almost since the dawn of history. Copper's uniform heat conductivity makes it a good material for top-of-range cooking because the heat is distributed evenly. This property also enables copper serving utensils to keep foods palatable.

     Copper cooking surfaces are usually lined with tin, stainless steel or coated with a nonstick finish because cooked foods left directly in contact with uncoated copper may become discolored. While it is not necessarily injurious to health, the discoloration tends to detract from the food's eye appeal.

     An electrolytic process that deposits copper on the bottom of a stainless steel utensil utilizes copper's superior heat distributions. Another manufacturing process bonds or laminates copper to stainless steel or other metals. A core of solid copper sandwiched between two layers of stainless steel is another way copper is used to distribute heat uniformly.

Use And Care

     Copper can be easily polished with various commercial copper cleaners. A mixture of flour, salt, lemon juice and ammonia or a mixture of vinegar and flour are two methods of keeping copper utensils shiny.

     After cleaning, wash in sudsy water and rinse before polishing with a soft, clean cloth. Tin linings may wear off with frequent use; the utensil can be retinned.

CAST IRON COOKWARE

Properties of Cast Iron Cookware

     Cast iron utensils have been with us for thousands of years. The Chinese apparently were the first to use them, producing cast iron bowls in which to cook and eat rice. That was nearly 3000 years ago.

     In Europe during the Middle Ages, cast iron utensils were considered so valuable that they were listed along with gold, jewels, and other riches of royalty. An iron foundry, where utensils and other cast iron products were manufactured, was one of the first industries organized in North America.

     Today's cast iron cookware has improved greatly over those of even the recent past. They are made of iron alloys that give additional strength to the utensil. And today there are cast iron utensils with colorful porcelain enamel exterior and interior finishes.

     Cast iron currently is used for utensils that include skillets, roasters and Dutch ovens, broilers, griddles, and some specialty items, such as muffin and corn bread pans. These utensils are excellent for browning, frying, stewing and baking foods.

Use and Care

     Natural cast iron utensils benefit from slightly different handling in the home that the techniques recommended for other materials.

     For one thing, natural cast iron usually is "pre-seasoned". It should not be washed with strong detergents or scoured. Instead, hot sudsy water may be used, and the utensil rinsed and wiped dry immediately.

     The inside of the washed and dried utensil should frequently be coated with unsalted cooking oil or shortening, just before using again, it should be wiped with a dry cloth or paper towel.

     Never store a natural cast iron utensil with the cover on, as this might cause sweating and consequent rust damage. Store these utensils in a dry place.

     Natural cast iron utensils can be re-seasoned if necessary. This is done by scouring the utensil thoroughly, washing it in soap and water and drying it, and then coating the inside surface with unsalted cooking oil or shortening. Then the utensil should be heated in a moderate oven for about two hours. When the utensil is removed from the oven, excess grease should be wiped away.

     Cast iron utensils with porcelain enamel interiors do not need seasoning. Hot sudsy water and thorough rinsing will keep them clean and shining.

TIN COOKWARE

Properties of Tin Cookware

     The genealogy of tinplate in the kitchen can be traced to ancient times. Tin was widely used in Egypt, although it was not found there. Daring Phoenician sailors ventured to the British Isles, then known as the Cassiterides or Isles of Tin, to obtain this precious metal.

     Tin plating-the process of plunging plates of iron into molten tin-was invented in Germany during the 16th century. The secret of using as a protective coating for metal was brought to England about 1670.

     In our age of new concepts in material and fabricating methods, tin-plated steel still plays an Important role, particularly in the baking industry. Many commercial baking utensils are made from tin-plated steel because it is durable and possesses excellent inherent baking qualities.

     The consumer market for this type of merchandise has also been important over the years to bakeware sales because of the utensil's economy and baking qualities.

     Very little care is required in using tin-plated bakeware. This steel-based material is highly resistant to denting and scratching. Tinplate provides the necessary protection that helps the steel resist rusting and staining.

PORCELAIN ON METAL COOKWARE

Properties of Porcelain On Metal Cookware

     Porcelain enamel on metal has served the needs of mankind for centuries. The exact time and place of its origin are not known, but measures throughout the world contain many examples that predated the birth of Christ. These ancient artifacts remain as bright, clean and well defined as the day they were created.

     Originally porcelain enamel was an artistic medium for making fine jewelry and, even when it was used to make a functional object such as an urn or small box, it was invariably fashioned in painstaking, handcrafted designs. For centuries porcelain enameling developed as an art form, with only gold, silver, copper and bronze used as its base metal.

     Then, in 1830, a Bohemian craftsman found he could create a permanent, smooth, glossy surface on cast iron by dusting the red-hot metal with dry, powdered porcelain-and a new era dawned. From that time on, porcelain enamel became a utilitarian as well as a decorative finish.

     Porcelain enamel is essentially a highly durable glass, which, with coloring oxides and other inorganic materials, is fused to metal at extremely high temperatures. It first found its way into the kitchen as a decorative finish for wood-burning ranges and cast iron utensils. Later, when techniques were discovered for applying it to sheet steel, it became a standard coating for coffee pots, roasting pans, and saucepans.

Manufacturing

     In the manufacture of cooking utensils, porcelain enamel is applied after the metal is formed into its final shape. It can be applied to carbon steel, aluminum, stainless steel, and cast iron.

     It is one of the most versatile finishes, offering virtually an unlimited range of colors and design effects. Today's colors include many shades of bright reds, vibrant greens, clear blues, sunny yellows, and warm oranges, as well as earth tones. Plaids, stripes, decorator designs, and even provincial prints can be found. There are also decorative porcelain decals, mechanically applied that have the same scratch and stain resistant qualities of the regular porcelain coating.

Use and Care

     Aside from the variety of colors and designs available, the chief recommendations for porcelain enamel are its stain and scratch resistance, its immunity to fading and peeling, its chemical resistance, and the fact that it will not pick up food odors.

     Porcelain enamel utensils can be used for cooking, baking, serving and storing food. Do not use porcelain enamel utensils over high heat for a prolonged time; extreme high temperatures may cause the porcelain to melt.

     Cleaning porcelain enamel is easy. Just wash in warm sudsy water, using a sponge or cloth. Burned-on foods or other stubborn stains can be removed by soaking or by using a non-abrasive cleanser and nylon or other non-abrasive scrubber.

     All porcelain enamel cookware that have a nonstick finish applied to the interior surface are safe in modern dishwashers.

GLASS, CERAMIC AND GLASS-CERAMIC COOKWARE

     In the 20th century, heat-resistant glass and glass-ceramic were developed. Like ceramic, they meet the need for attractive ware used for mixing, cooking, serving, and storing.

     Major features are attractiveness, one-dish convenience, and inert non-porous surfaces that won't absorb food odors or flavors. For easy cleaning, both glass and ceramic ovenware are available with nonstick interiors.

     While most are very rugged, they can break under impact. However, some glass, ceramic and glass-ceramic cookware manufacturers warranty their products against thermal breakage, and offer free replacement should the ware break in normal use within the warranty conditions.

     Heat-resistant glass cookware may be made of clear or tinted transparent material or opaque white (commonly called "opal" glass). Glass-ceramic cookware may be white or transparent and tinted. Ceramic cookware is available in white or a variety of colors.

Properties of Glass, Ceramic And Glass-Ceramic Cookware

     Heat resistant glass can be used for storing, cooking and serving. Some pieces can be used on the rangetop, while others are suitable only for the oven. Those designed for baking can be taken from refrigerator and put into preheated ovens after the utensil reaches room temperature.

     As a rule, they should not be used on the range top or under the broiler. Heat-resistant glass range top products should always be used with a wire grid on an electric range but should never be taken from the refrigerator or freezer and placed directly on a hot range top element.

     Similarly sudden cooling may be harmful to glass cookware. Hot glass cookware should not be allowed to come in contact with wet countertops, nor should they be placed in water while they are still hot.

     Some ceramic cookware is made of heat-resistant material, which can go from the freezer to a hot oven or microwave. None is suitable for top-of-range or broiler use.

     Like glass cookware, ceramic cookware holds heat for a long time while providing the additional benefit of an attractive serving dish. Ceramic cookware is available in a wide variety of shapes, colors, and designs.

     Among the most thermally shock-resistant material ever developed by man, glass-ceramic is a true space-age material. It was first used in rocket nosecones because the glass-ceramic material could take the extreme temperature changes encountered in their supersonic flight from the earth's surface into outer space and back.

     Glass-ceramic cookware offers wide food preparation versatility. It can be used for rangetop cooking and is excellent for roasting, broiling or baking -in the conventional or microwave oven. It can go directly from the freezer to the rangetop, broiler or hot oven. Glass-ceramic cookware can be immersed, hot off the stove, into sudsy dishwater for easy cleanup.

Manufacturing

     Glass is a non-crystalline material manufactured by melting a combination of raw materials including sand, soda ash, limestone, feldspar and borax. The glass used in cookware is normally melted in a large refractory furnace or tank at temperatures exceeding 2000 F.

     A small portion of the molten glass is drawn out of the tank and is blown or pressed in a mold. The mold essentially cools the glass causing it to solidify. Following forming, the glass article is cooled to room temperature on a schedule specifically designed to insure development of the desired heat-resistant characteristics.

     A glass-ceramic is a special glass composition, which is melted and formed like heat-resistant glass. Following forming, the glass articles are subjected to a special heat-treating schedule resulting in the development of a fine crystalline structure throughout the article. It is crystalline structure (which may be transparent or opaque) that gives the glass-ceramic its unique performance characteristics.

     Ceramic cookware is manufactures from a mixture of water, clays, fluxing minerals (often feldspar) and finely ground sand. The particular forming method used depends largely on the water content of the mixture. A high water content (relatively liquid solution) permits casting of the ware in a mold. A lower water content results in a plastic mass, which can be forced into the desired shape by a variety of methods.

     After forming, the ware is dried and fired (subjected to temperatures in excess of 2000 F.) in a ceramic kiln to bond the components of the "body" together. Following this initial firing, the surface of the ware is coated with a glaze which, upon firing in a second ceramic kiln, develops a smooth non-ceramic cookware with a nonstick interiors three layers of nonstick coating are applied to specially prepared interior surfaces and then cured at approximately 800 F.

Use and Care

     Ceramic, glass and glass-ceramic materials are excellent retainers of heat. Baking dishes and casseroles made of these materials hold the food's heat long after it is removed from the oven. It is usually recommended to use these items at slightly lower temperatures for a shorter length of time because the covered cookware continues to cook foods even after it's been removed from the oven. A rule of thumb is to reduce the oven temperature about 25 F (14C).

     Check the manufacturer's recommended care and use instructions before using any glass, ceramic and glass-ceramic bakeware. These items are usually cleaned with hot sudsy water and soaked if food has been burned on the item. Avoid knives, sharp kitchen tools, scouring pads and abrasive cleaners so that surfaces remain in their original smooth finish. This is especially important for ovenware with nonstick interiors. Nylon and plastic scrubbers are acceptable for stubborn sticking problems.

NONSTICK FINISHES

     Efforts to ease the homemaker's kitchen tasks have received a solid boost in recent years with the development of nonstick finishes on cookware interiors and exteriors. The advantages of nonstick surfaces are obvious. They clean easily and quickly. Grease and food can be washed away with a sudsy sponge. A dieter can fry food using less fat, and the food won't stick to the utensil.

     Fry pans were the first utensils to be given nonstick finishes. Now almost every cookware and bakeware item is available with a nonstick surface. There are griddles, saucepans, casseroles, muffin pans, cookie sheets, Dutch ovens, egg poachers, cake pans, deep fryers, waffle bakers, and many others.

     Many accessories have been introduced. There are nonstick finished kitchen tools, such as spoons, spatulas, and egg beaters, for use with nonstick cookware. There are items that work better or are easier to clean when coated with a nonstick finish, such as rolling pins and ice cream scoops.

     Basically, nonstick finished utensils should be used and cared for in the same manner as metal cookware and bakeware. Before first use, the utensil should be washed in hot sudsy water, using a soft sponge or dishcloth. It should then be rinsed and dried. Do not use abrasive scouring pads or powders.

     Many manufacturers recommend that nonstick fry pans, Dutch ovens, and bakeware be seasoned with cooking oil before they are used for the first time. Cooking oil should be wiped on the nonstick surface with a paper towel - and the utensil is seasoned.

     An exception is the tubed angel food cake pan. It should not be oiled or greased if it is used for angle food or sponge cakes, because the batter must cling to the sides of the pan during baking time.

     For baking cakes that contain fruit or a great amount of sugar, greasing usually is necessary to insure complete release of baked goods from the surface of the utensil.

     In most cases, simply use nonstick bakeware just like any other bakeware, following recipe instructions for greasing and flouring baking pans. Most homemakers find that oils, fats and butter may be desirable in frying, not to prevent sticking, but to contribute to the flavor of foods and also to aid in even browning.

     Eggs have a tendency to stick slightly; however, cooking them with a small amount of fat aids in the release from the pan.

     High heats should be avoided in most top-of-range cooking and particularly with nonstick utensils. "Low" to "medium" heat settings will give excellent cooking results without either warping the utensil or staining the nonstick finish, as well as making cleaning easier.

     Use detergents in washing a nonstick pan after every use, so that grease or residual food will not cling to the interior. Pans may need to be re-seasoned after each washing in an automatic dishwasher. Be sure to place coated pans carefully in the dishwasher so that they will not be scratched.

To Remove Stains

     Simmer any of the following solutions 15-20 minutes in the stained pan:

• 1/4/Dip-It* Coffee Pot Cleaner in 1 qt water OR;
• 3 Tbsp. Snowy Bleach** (oxygen bleach for delicate fabrics) and 1 tsp. Liquid dish detergent in cup water OR;
• 3 Tbsp. Automatic-dishwasher detergent in 1 cup water.

     Rinse, dry and again "condition" with shortening or cooking oil.

     Non-stick finishes may be scratched by sharp or rough-edged kitchen tools. The scratches effect only the appearance, not nonstick properties of the finish. Scratches do not widen, nor will the finish peel, chip or blister if it has been properly applied.

     While smooth-edged metal tools can be used on hard-coat nonstick finishes, it is suggested that you follow manufacturer's instructions.

     Some of the familiar names for nonstick finishes are "Teflon", "Ultralon", "SilverStone", "Xylan", fluorocarbon, and silicone. In addition, there are nonstick cooking sprays that you can apply to uncoated cookware before each use. They are vegetable, oil-based products packaged in cans or bottles which are available at grocery stores. These vegetable coatings are not a permanent finish.

*Economics Lab., Inc., St. Paul, MN 55102

**Gold Seal Co., Bismark, ND 58501