Bricks

brick wallWhen was the last time you looked at a brick wall? I mean really looked at it. I know what you’re thinking: “Why would I?” Well, there’s a lot more to brickwork than you’d realise. Anyone who has heard the story of the Three Little Pigs knows that bricks create a safe and stable structure in which to live or store goods. But over the millennia of their history they have often been much more than that.

Back in Tudor times bricks were the preserve of the rich. The amount of work involved, in preparing the clay, shaping individual bricks, and firing them, made them an expensive material. Noblemen across England showed off their status by investing in vast brick mansions, often with contrasting-coloured patterns built in.

A few technical terms:

  • Course means a horizontal row of bricks.
  • Diaper work is a pattern of bricks in a different colour from the main body, particularly in the form of a criss-cross design.
  • Bricks have short ends – headers – and long sides – stretchers.
  • The right-angled edges are called arisses.
  • The dent where the mortar goes is called a frog.
  • The brick height is called the gauge. Tudor bricks are typically much shallower gauge than modern ones.
  • Bond is the way in which headers and stretchers are mixed to create the overall pattern.

Bricklaying bonds have changed over the years. For example, modern brickwork tends to be what’s known as stretcher bond, where all the long edges face the front.

This mostly came about because of the advent of double skin houses with a cavity between the two walls. The idea was that an air gap would help insulate the house, because air is a poor conductor of heat. But the popularity of cavity wall insulation a few years ago has shown that wasn’t practical.

Earlier construction used different patterns.

Bricks in alternate courses of headers and stretchers are known as English bond. The wall is, of course, two bricks wide because the headers are twice the length of the stretchers. Other bonds include Flemish, which consists of rows of alternate headers and stretchers, with the headers centred on the mid-point of the stretchers; herringbone; and the very complex rat trap bond, which has half-gauge bricks mixed in.

Iron

Iron figurine from 10 North Street, Cromford, Derbyshire

There are three main types of iron that should be considered: wrought, cast and steel.

Wrought Iron has a melting point of 1535 degrees C so it comes out of the furnace solid and is worked solid. It is hammered into shape and forms a tough finished product. It is good for tools and swords. It has less than 0.3 per cent carbon content.

Cast Iron comes out of the furnace molten and is poured into moulds to make its shape. It is brittle so it does not produce good tools or edged weapons. Often it is used for decorative objects. It has more than 2 per cent carbon. These two forms are dependent on the type of ore available, high-carbon ores will not make good wrought iron. Chinese ores, for example, are useful only for cast iron, which is why there is so much decorative Chinese ironwork.

Steel is a combination of iron and the right amount of carbon – between 0.3 and 2 percent – which makes it particularly tough and flexible. It is capable of holding an edge and is therefore very useful for tools and weapons. It is, however, very difficult to manufacture and involves “cooking” the iron and carbon together for many hours at more than 1100 degrees C.

The “Three Age” history of the introduction of iron in Europe is unique and not reflected anywhere else in the world. In southern Africa, for example, there never was a Bronze Age and the first metal to be used was iron. In North America native copper was hammered into shapes but was never smelted. In Europe the Iron Age followed the Bronze Age but there was no distinct line between the two. Iron was merely an additional metal. It is difficult to form into complex shapes, unlike bronze, and it corrodes easily so it was not a suitable material for all uses. By the 2nd millennium BCE a few iron items were in circulation, such as pins and awls but around 1100 BCE the metal took off in a big way. It appeared throughout the near east, Europe and Britain almost simultaneously.

There are two sources of iron – meteoric iron is extremely rare and can be identified by its high nickel content, iron ores are naturally occurring in the earth’s crust.  Ores appear as oxides and sulphides; both are commonly available. Iron ore is rarely pure so there are almost always other constituents in any iron item. Unfortunately it is impossible to assign chemical “signatures” to European ores because they vary so much, so the inclusions are not useful for sourcing raw materials used in archaeological artefacts.

Thanks to Prof Elizabeth Slater (RIP), head of department at the University of Liverpool school of archaeology for clear lectures on artefacts and materials. J M Cronyn’s Elements of Archaeological Conservation has also been consulted.