Harrow and Hillingdon Geological Society
Bricks are commonplace, but definitely not unremarkable. They have a fascinating history in this country dating back to the time of the Romans. Romans bricks were tile-like objects, 18in square and 1in thick. They were jointed with lime mortar to construct walls, piers, arches, etc.
After the Romans left Britain in 412 AD these techniques were lost and wood was again used for most buildings, although old Roman bricks were recycled to construct religious buildings. St Alban's Cathedral was built from old Roman bricks in the 12th Century, which means they are now about 2,000 years old.
The technology for making bricks was re-introduced to East Anglia in the 13th century from northern Europe, stimulated by the strong trading links of the Hanseatic League. These bricks were different from the Roman ones; they measured approx. 9in x 4in x 2in deep. The bricklayers were highly skilled and the bricks expensive, being made for a particular building. An early example is Tattershall Castle in Lincolnshire (1435). Brick won favour with rich and powerful men in the 15th and 16th centuries. Henry VIII’s Hampton Court was built in the early 1500s. In the centuries since brick has gained in popularity to become one of the staple materials of British building.
Clays are of numerous types and hence produced many types of brick ranging in colour from buff to red to blue-black. Early bricks were of soft alluvial clays from river valleys. The clays were mixed with water to a mud-like consistency by foot or using horse powered mills - in small country works these simple methods continued until the 1930s. Sometimes about 10% ground anthracite is added to the clay mixture to improve firing. Traditionally the bricks were made by hand using a frame mould placed on wooden stock that forms the bottom of the mould. On the stock is a kicker that shapes the recess or frog in the bed surface of the brick. The mould is wetted and dredged with sand and a clot of clay is dashed into it. Excess clay is cut off and the brick is turned out of the mould and left to dry.
The bricks are then fired. The simplest method is in a clamp – a stack of bricks (½ to 1million) on a layer of coke. The bricks are covered with previously fired bricks and the coke lit. It takes about a month to build a clamp, a month to fire it and a month to draw and sort the bricks. Some are fired better than others and can be used to build external and load-bearing walls. Others would be used for interior and non load-bearing walls. To speed production and control firing kilns were developed – permanent structures to contain the process. Smaller quantities were handled, but much quicker – about 7–10 days.
Traditional methods are still used today, particularly in southern and eastern counties. However, in the 19th and 20th centuries brick making was mechanized to meet the huge demands of expanding society and commerce. Modern works use machines that press bricks or others that extrude the clay into long rectangular columns that are then cut into bricks by taut wires. Modern firing methods are also highly developed using continuous firing kilns. As a result bricks are made much faster and the quality is very consistent.