A brickfield is a field or other open site where bricks are made. Land may be leased by an owner to a brickmaster, by whom the manufacture of bricks may be conducted. Historically, the topsoil was typically removed and the clay beneath was stripped and mixed with chalk and ash to make bricks. In pre-19th-century England, [i]n most areas the brickfield owner hired a brickmaster at a price per thousand bricks to superintend the site and take full responsibility for the output of the operations. He in turn contracted with moulders to temper, mould and hack the bricks. Each moulder then hired his own 'gang' of subsidiary labourers and acted as their employer. Subsequently, the field (if not too damaged ecologically) could be used for horticulture. In Kent such fields were often planted with fruit trees. Brickfields were mainly created from 1770 to 1881, when a new shaly clay was discovered at Fletton. This period coincided with the housing and railway boom in London and cheap river-transport in Thames sailing barges. Brickfields existed elsewhere, but often the clay layer was deeper or there was no chalk nearby. In modern times bricks are made at a brickworks.
"Brickyard" can serve as a synonym of "brickfield".
Brickfield or Brickfields became a common place name in southeast England.
Geology
The southeast of England consists of rock strata that are more recent than most of Great Britain. It consists of a large denuded anticline, an anticline that has been eroded away leaving a series of escarpments separated by low lying vales, The Cretaceous ridges are known as the North Downs and South Downs. The Downs have been cut through, with the Medway Valley being the most prominent. The Hoo peninsula is an Eocene (Thanet sands) ridge. The London basin is an Eocene structure composed of London Clay. All this solid geology is covered with a layer of brown structureless loam (Head), and muds deposited by the rivers. Both the head and the fluvial mud are called brickearth. Water is also needed, the rivers are saline so wells and boreholes need to be dug through the three Cretaceous chalk layers to the impermeable Gault Clay.
Taking the parish of Frindsbury as a referenced example: about of acidic topsoil covers about of head, which lies on the alkaline Thanet Sands. There are five layers of sands with different properties – the light grey sands are themselves marketable and are used in the brickmaking process, and as moulding sand for metal foundries.
Process
A field was leased from the farmer and it was 'uncallowed' (the topsoil removed). The soil had been farmed and in the Medway area it had been chalked every five years with 'fat chalk' extracted from the 'dene holes'. The head, or clay was now dug from the field in winter by workers (diggers) on piecework rates. This was calculated on the volume extracted. 44 ft by 8 ft by 6 ft would make 33000 bricks. The dug clay was left exposed in heaps to weather.
Washmill
The washmill was usually a sunken circular pit that was brick lined. It was deep, and in diameter. A horse pulled a centrally pivoted beam with rakes that broke up the weathered clay and mixed it into a slurry. It was here that the correct proportion of chalk, some river mud and even rags were added. The rags would help the combustion. Clay alone would be too brittle. The popular Kentish yellows (London stock bricks) used 10-17% of chalk. The surface of the porous yellow stock, reacted chemically with the sulphur dioxide in the polluted air to form an impermeable glaze as well as an attractive colour.
Washback
When the liquid slurry was ready it was 'laundered' along wooden pipes into square washbacks, the water seeped away leaving a stiff clay mix . This process was dependent on the weather.
Brickmoulding
The brickmaking was done by 'gangs' of persons who were usually a family unit. They each had a 'berth', situated in front of a washback. It contained a bench with a pugmill behind. The pugmill had an inlet hopper, and moved the clay mix along a six-foot tube using an Archimedes screw. The pugging process cut up the clay and made it more pliable. Pugmills were attached to a power source by lineshafts and belting.