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Cast iron is not pure iron, but a mix of iron, carbon, and silicon. It is versatile and used in pipes, machine parts, and pans. Proper seasoning is required for cooking. Cast iron bridges were used in the 18th and 19th centuries, and it was a breakthrough in the building industry in the early 20th century.
Cast iron has become synonymous with durability: a cast iron stomach or alibi. As far as metals go, though, it’s actually a kind of Brunswick stew. While the cast iron that forms its base is melted, scrap iron and steel are often thrown into the mix.
When the process is complete and impurities such as sulfur are removed, the final product is actually only 95% iron. The rest of the chemical composition is mainly carbon and silicon, in various percentages. Anything above 2% silicon is known as “grey cast iron”, while a smaller amount gives rise to “white cast iron”. The “white” form isn’t actually white, but gets its name from a reaction with increasing 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 for industrial applications, because it makes the metal more malleable and therefore quite versatile. Its first application in 17th century China was as cannonballs and shots. Today, it’s used in pipes, machine parts, automobile components, and perhaps most commonly, pans.
The cast iron skillet that served a cook’s great-grandmother so well has enjoyed something of a comeback in recent years, as some people have grown wary of Teflon® coatings as potentially harmful to health. With this awakening, however, has come a renewed awareness that using this metal for cooking often requires considerable vigilance.
Unless properly “seasoned,” cast iron can often cause cooked foods like eggs to stick to the surface. Unlike non-stick cookware, cast iron actually binds to fats and oils to change its surface, so the longer a pan made with this metal is used, the easier it becomes to use. Many professional chefs are fans of the metal, praising it for its heat retention and evenly radiating surface.
Cast iron bridges are generally relics from the 18th and 19th centuries, although some survive. The use of this metal was also considered a breakthrough in the building construction industry in the early 20th century due to its load-bearing capacity, but it faded into the background when new forms of steel were introduced to take its place . After the collapse of the World Trade Center towers on Sept. 19, a large cast iron cross was dug out of the rubble, still intact.
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