To make decorative wrought iron fences, manufacturers work with architects to create blueprints for the project from an initial design idea; in some cases, they may use computer assisted drawing software to perfect the plans. Next, a blacksmith prepares the iron by heating it in a forge. When the iron is hot, the blacksmith uses hammers to bend and shape it to match the blueprints. Fabricators then weld the iron together to create the fence.
When the iron has been properly shaped and welded, workers smooth the surface with an abrasive blasting process. They then galvanize the metal with a coating of steel or zinc to protect it from corrosion. Fabricators may also attach finials to the top of the fence using screws. To finish the project, they paint the galvanized fence; common colors are black and white.
Modern iron working arose in the late 18th century, when blacksmiths first began to prepare iron through a process called "puddling." During this process, workers heated iron in blast furnaces to rid it of impurities. Between the beginning of the Iron Age and the advent of modern manufacturing techniques, smiths added crushed limestone or seashells to heated iron to purify it.
The more iron is heated, the stronger it becomes; this is due to wrought iron's low carbon content and the presence of slag that makes the metal more flexible. Therefore, the puddling process also strengthened the iron. Puddled iron was then shingled; during this process, blacksmiths further purified the iron by hammering it. They refined the metal by reheating it and hammering it until it became flat and elongated. Iron mills processed the hot iron into puddled bars, which could be reheated and shaped into ornate structures.