How Are Wrought Iron Rails Made?

An Ancient Craft

Wrought or "worked" iron is a material that was first used by the ancient craftsmen of China and Rome for decorative and domestic items, such as doors and furniture. Cast iron, the metal of choice for the early Industrial Age, was economical but unable to carry heavy loads. Wrought iron was stronger than cast iron and oxidized more slowly due to its denser structure. It eventually became the material of choice for load-bearing structures like bridges and buildings. The reign of wrought iron as a building material was short--just about a single century. By the end of the 19nth century, it had been largely replaced by cheap, easy to produce steel. Up to half as expensive to produce, steel was far less labor-intensive and less likely to bend under stress than wrought iron, important qualities as the age of the skyscraper dawned. The hand-crafted nature of wrought iron, though, still makes it the material of choice for restorations, particularly in grille work and railings.

Smelting and Puddling

Iron is a mineral; iron ore comes from the ground, threaded through rocks and intertwined with other minerals. The first step toward making wrought iron is to grind the rock and separate the ore from the rock, often using giant pans and screens reminiscent of the ones that gold prospectors used to use. This ore is not pure. It contains other minerals and must be melted to draw off the extra minerals. Most of these minerals float to the top of the molten iron as "slag" which is drawn off the top of the ore. A silica-based slag is left in the molten iron and the iron super-heated to burn off (or oxidize) excess carbon and then drawn out of the oven for use. Medieval furnaces used charcoal to cook iron ore but by the 19th century, indirect heating in coal furnaces were the norm. Steel was drawn from the chamber and stirred, or "puddled," to draw off vaporized impurities including carbon dioxide and carbon monoxide. Today, only a few smelters of wrought iron remain.

Working the Iron

Once it is drawn from the smelting oven, the hot iron is fashioned into sheets or rods of various sizes and shapes. Iron is re-heated until it glows red-hot. The iron "smith" holds the piece with heavy iron tongs and works it gradually into shape with a variety of pounding, shaping and turning tools until the piece takes its final shape. The smith may need to re-heat the piece several times to achieve the final shape. When the posts, rails and decorations are all made, a welder will assemble and join them to form a finished railing.

References

• Wrought Iron Process
• The Real Wrought Iron Company

Resources

• Read this Article in Spanish
• The Fabricator: Wrought Iron
• The Production, Microstructure and Properties of Wrought Iron