A-Z of industries
by Graham Brooks
(Page created 19/04/05. Last updated 20/08/12)
Most bricks are made from clay, which is usually composed of aluminium silicates, derived from weathered rocks. When clays are heated they change their chemical structure. The water of crystallization in kaolinite (that water which is chemically combined with the clay crystals) is irretrievably driven off at 400oC. At 1770oC it reaches itís melting point. Between these two temperatures there is the sinter point, this is the point were the edges of the clay particles melt and fuse together. Also there is the maturing point, this is the temperature which produces the densest structure in the fired clay, without it melting and distorting.
Mixtures of clay with other minerals, either naturally or artificially added, lower the temperatures at which the above reactions occur. Natural clays therefore have a wide range of maturing points depending on the other minerals they contain. Part of the art of brick making was to determine this for the clay being worked. The other minerals also determined the colour if the finished bricks after firing.
Brick making has taken place in Cumbria since the roman period and up to the middle of the 19th century the techniques were basically the same.
The clay was extracted usually from pits dug in the ground, these were usually near to the site at which the bricks would be required. Due to the bulky nature of the clay it was usually easier to move the fuel to the clay and then transport the finished product away. The clay was usually dug by hand in the autumn, the size of the clay pit was determined by the amount of bricks required (3 cubic yards of clay produces approximately 1000 bricks) and the ability to remove the clay from the pit manually.
Most clays required some form of processing before they can be formed into bricks. This originally involved leaving the clay to weather, especially by frost, so it was left to stand over the winter period. It was occasionally turned and any stones were removed.
The clays were then mixed to a homogenous consistency initially by hand and later by the use of pug mills. These initially would have been horse powered, but, later steam powered mills were used in the bigger brick works.
With the development of steam power it was possible to process the clay with machines and so remove the need to leave the clay to stand over the winter. This allowed brick making to become an all year round activity.
Once the clay had been formed into an homogenous mass it had to be moulded into the required shape. This was initially carried out by hand using wooden moulds on a portable table. A suitable size piece of clay was thrown into the mould and forced into the corners, the excess clay was then scraped off the top and the brick was turned out of the mould.
Various brick making machines have been invented over the years. These either forced the clay into the moulds to form individual bricks, because the pressure applied was greater than could be obtained by hand, these bricks are usually denser than hand produced bricks and are more uniform in shape and density. Or the extruded the clay through a die, this was then cut by wires into brick sized pieces.
Because clay contains a large amount of water it requires to be dried before it is fired. Otherwise the water expands and damages the finished product. The bricks were laid out to dry usually in the open air with a temporary cover to protect them from the worst of the weather. This usually meant that brick making was a summer activity after the clay had been weather over the winter.
Eventually drying chambers were installed at the larger brick works which usually used hot air either as waste from the kilns or from a specific furnace of its own.
Once dry the bricks need firing, the simplest method to do this is with a large pile of bricks and fuel mixed together and ignited. The main problem with this is there is little control over the final temperature. Usually some bricks were over heated and so distorted, whilst others were left under fired and too soft for use.
Most sites had some form of permanent kiln, the most basic of these are the updraught kilns. These range from the Scotch kiln which is basically four walls with fire holes in the sides which lead under a perforated floor onto which the bricks were stacked. The heat passed up through the bricks and out of the top of the kiln.
There are a large number of variations on this with baffles and various flue systems which control the flow of the gases and heat through the kiln and so the temperature obtained in the kiln. The development of these kilns eventually lead to the development of the downdraught kilns were the heat is pulled through the bricks from the top due to a draught from a large chimney.
Most of the smaller brickyards had single fire kilns. Here the kilns were loaded with bricks the kilns were lit and the bricks were burnt and the kiln was allowed to cool before the bricks could be removed. This cycle usually toke about one week. The larger brick works built continuous kilns based on the Hoffmann design. These had a series of interlinked chambers usually on an oval design. Wet bricks were stacked in one chamber and warm flue gases from a previous chamber, which was been fired, were drawn over them to dry them. The firing point was slowly moved around the series of chambers by adding fuel to the chambers usually from above. This allowed for the continuous burning of bricks.
In Cumbria especially in the north and west of the county in the 19th century a large number of small brick works were established. This was mainly due to the rising demand for new buildings and a regional supply of suitable building stone, which lead to an increase in price. Initially, especially in the Carlisle area, the bricks were made on or close to the site the building was to be built. The whole process would be by hand and would take about nine months to produce the bricks for the job.
Eventually as the technology developed permanent brick works began to be built. These were usually over the better beds of clay. These sites not only produced bricks but also roofing tiles, drainage tiles (important in a predominantly agricultural area) and other clay products.
Most of the sites closed down before or shortly after the Second World War, the clay pits have been filled in and the buildings removed. The best surviving example of a small brick works in Cumbria is the Lonsdale Brick and Tile works. On this site the remains of the clay pits are still present along with the moulding and drying shed. Two downdraught kilns still remain also. This site is unfortunately private.
All that now remains of many brick works is the bricks that they made. Fortunately a lot of brick works stamped their name on their products and so it is still possible to trace this industry.
Bricks and Brickmaking: Martin Hammond, Shire Album 7
Bricks to Build a House: John Woodforde, A London Brick Publication.
Brick Kilns an Illustrated Survey; Martin Hammond Industrial Archaeology Review Vol 1 no 2 Spring 1977.
The Roman Tileries at Scalesceugh and Brampton; R Bellhouse Cumberland and Westmorland Antiquarian and Archaeological Society Vol 2 lxxiii.
Carlisle brickmakers and Bricklayers 1652-1752; B. Jones Cumberland and Westmorland Antiquarian and Archaeological Society Vol 2 lxxiii.
Cumbrian Brick and Tile Works: North Cumbria; G. Brooks The Cumbrian Industrialist Volume three. The Cumbrian Industrial History Society.
Reake Wood Tile Kiln; T. Keates The Cumbrian Industrialist Volume one.
Newland Firebricks - some notes : Jonathan Wignall, CIHS Newsletter, April 1990
Wythop Silica Brick
MORE SITES TO VISIT
|Lonsdale Brick and Tile Works, Cumwhinton, Carlisle||NY 468515||A series of Victorian brick kilns, still standing but not in use|
|Clay pit, Barrow-in-Furness||SD195703||Pit, now flooded, from which clay was excavated for the Walney Road works of the Furness Brick and Tile Company.|
|Brick works, Askham||SD218762||The present site of the Furness Brick and Tile Company|