Context 139 - May 2015

10 C O N T E X T 1 3 9 : M A Y 2 0 1 5 CHRIS TOPP Wrought iron, yesterday and today Wrought iron has not been made since 1974, but some is available and in recent years the blacksmiths of Britain have slowly taken up the ancient ironworking skills again. Wrought means ‘worked’, which refers to the method of manufacturing the metal by working repeatedly under a hammer. In the past the work of the blacksmith became known as ‘wrought ironwork’, a name that has persisted for the art form even though the metal in use may not be wrought iron. Today the common material of the blacksmith is mild steel, a cheap industrial product lacking many of the virtues of its ancestor. Wrought iron is a two-component metal consisting of iron and a glass-like slag. The slags are in effect an impurity, the iron and the slag being in physical associa- tion, as contrasted to the chemical alloy relationship that generally exists between the constituents of other metals. Wrought iron is the only ferrous metal that contains siliceous slag. It is to this slag that wrought iron owes the properties, which are of interest to the conservator and the blacksmith. There are essentially two types of wrought iron: ‘charcoal iron’, made in a charcoal fire and used from the iron age to the end of the 18th century, and ‘puddled iron’, made from cast iron in an indirect coal-fired furnace, and used since the dawn of the modern industrial era. Historically wrought iron has been worked by black- smiths, using traditional techniques in both forging and construction, to make high-end decorative wrought ironwork. Today the term wrought iron is becoming debased and misinterpreted, to cover all ornamental ironwork, including cast iron and mild steel, as well as incorporating modern construction techniques. The difference in quality and value is enormous. Whereas it would be unthinkable to repair historic stonework with concrete or cast stone and Portland cement, it is common for historic wrought iron to be repaired using mild steel and electric welding. Wrought iron has been used in building from the earliest days of civilisation, wrought-iron door furniture being common in Roman times. The structural use of iron dates from the middle ages, when bars of wrought iron would be used occasionally to tie masonry arches and domes.This use of wrought iron in tension guaranteed its use throughout the ascendancy of cast iron in the canal and railway ages, as cast iron is strong only in compression.The ill-fated first Tay Bridge was of cast iron beams tied with wrought iron. The demand for higher dynamic loads in bridges and warehouse buildings, and the ever-greater spans of train sheds towards the end of the 19th century, led the designers of buildings to acquire the technology developed to build ships of iron, and create beams of riveted wrought-iron rolled sections. By the turn of the century this had led to buildings completely framed in wrought iron, and later steel girder sections, and cast iron was once again relegated to an ornamental role. Our main concern with wrought iron, however, will be in its application to gates and railings, frequently given an ornamental treatment by the blacksmith. There are wrought-iron railings inWestminster Abbey from the 13th century which, in essence, display all the characteristics, which we have come to know as ‘wrought Australian blacksmith Dave Fleming forging at Chris Topp’s