Cast iron or wrought iron?By Mark Chervenka
Cast iron or
Ornamental ironwork is generally of two types, wrought or cast. Cast iron is made in molds; wrought iron is formed, or forged, by hand. Cast iron is generally a means of mass production dating primarily from the mid-18th century on; wrought iron has been worked since ancient times.
The two types can also be divided by the amount of carbon present. Wrought iron typically has only .03 to .04 (three- to four-tenths of one percent) carbon; cast iron includes about 2 to 6 percent carbon. Low carbon wrought iron is softer and easy to work with at the forge. The higher carbon cast iron is brittle and hard. The low carbon also makes wrought iron very rust resistant and well suited for outdoor use. Cast iron surfaces, with the higher carbon, rust almost immediately if not treated with a surface coating such as paint or a patina.
The so-called "wrought iron" sold today in building supply centers is generally a type of mild steel with no similarity to true wrought iron. The new wrought iron railings are almost always hollow. Similar railings made of true wrought iron are solid.
Most iron Victorian lawn and garden furniture and ornamental containers are made of cast iron. Iron fences, gates, balconies and architectural details made during the Victorian era were also generally made of cast iron but before ca. 1860, these types of items were usually wrought iron. There are several clues to help you distinguish wrought iron from cast iron.
Most wrought iron will have hammer marks or an irregular surface as a result of hand forming. Cast iron will usually have a uniform surface having been produced in a mold and usually show only mold or seam lines. Inside 90° corners of most wrought iron fences, railings, etc., form a sharp angle and outside 90° corners are rounded (see Figs. A-B below). This is because inside corners were hammered over a square-edged bar or anvil while outside corners were simply bent over. Both inside and outside 90° corners of cast iron are perfectly square because they were cast in a mold, not hand formed. Most hand worked wrought iron is fully three dimensional and is solid metal. Cast iron, made in a mold, frequently has a design or pattern only on one side. Larger pieces of cast iron are almost always hollow.