What Is Cast Iron?
Cast iron has become a synonym for durability — a cast iron stomach, a cast iron alibi. As metals go, however, it is actually something of a Brunswick stew. While the pig iron that forms the basis for cast iron is being melted, scrap iron and steel are often thrown into the mix.
When the process is complete and impurities such as sulfur are subtracted, the end product is actually only 95 percent iron. The rest of the chemical makeup is primarily carbon and silicon, in various percentages. Anything over two percent silicon is known as "gray cast iron," while a lesser amount gives birth to "white cast iron." White cast iron is not actually white, but gets its name from a reaction with the increased carbon that creates small white deposits of cementite on an otherwise dark surface.
Despite its metaphorical reputation, cast iron is more brittle than pure iron and steel, and melts at a lower temperature. This is not a bad thing as far as industrial applications are concerned, because it makes cast iron more malleable and thus quite versatile. Its first application in 17th-century China was as cannonballs and shot. Today, it is used in pipes, machine parts, automobile components and, perhaps most commonly, skillets.
The cast iron skillet that served your great-grandmother so well has enjoyed something of a comeback in recent years, as some cooks have become wary of Teflon® coatings as possibly unhealthy. With this revival, though, has come renewed awareness that using cast iron for cooking often requires considerable vigilance.
Unless it is properly "seasoned," cast iron can often cause cooking food such as eggs to stick to the surface. Unlike Teflon® cookware, cast iron actually bonds with fats and oils to modify its surface — thus, the longer a cast iron frying pan is used, the more user-friendly it becomes. Cooking show superstar Emeril Lagasse is a leading proponent of cast iron, which he praises for its heat retention and evenly radiating surface.
Cast iron bridges are generally relics of the 18th and 19th centuries, although some survive. The use of cast iron was also considered a breakthrough in the early 20th century building construction trade because of its weight-bearing capacity, but it moved to the sidelines when new forms of steel were introduced to take its place. After the World Trade center towers collapsed on 11 September 2001, a large cast iron cross was dug out of the wreckage, still intact.
Written by Darrell Laurant
