The Doric Columns
AGREEMENT FOR SERVICE, made this (31st) day of (March) 1883,
In the 19th century, and previous centuries, brickmaking was a seasonal occupation, due to the clay needing to be weathered. The clay was dug out during the autumn and left to weather in the frosts of winter. This was done so that the clay was broken down into lumps . In April the clay was turned over, or put into a pug mill (a grinding machine which was driven by a horse, or later by an engine). At this point, the stones and pebbles were removed. This had to be done because if left in the stones and pebbles would cause the brick to crack when fired. After further milling and processing the clay was ready to be made into bricks
Early Brickmakers had to dig for the clay on site with hand shovels. This was done in autumn. The Brickmaker chose his clay by it's colour and texture and based on his experience. He sought clay that was located just under the topsoil to minimize the hard work of digging it with hand spades. The clay was exposed to the weather so that the freeze-thaw cycle of the winter could break the clay down and allow it to be worked by hand. The winter made the clay soft and removed unwanted oxides. In the spring the clay was then able to be worked by hand. It was necessary to either grind the clay into a powder and screen it to remove stones or the clay was was placed into a soaking pit where it was mixed with water to obtain the right consistency for moulding. It was kneaded with the hands and feet to mix all the elements of the clay together. This step was called tempering or pugging and was the hardest work of all. In the mid-1800's horse driven pug mills were invented.
The clay was removed from the soaking pit or pug mill by a temperer who delivered it to the moulding table. The assistant brick moulder was called the "clot" moulder and he would prepare a lump of clay and give it to the brick moulder. The brickmoulder was the key to the operation and he was the head of the team. He would stand at the moulding table for twelve to fourteen hours a day and with the help of his assistants could make 3500 to 5000 bricks in a day. He would take the clot of clay, roll it in sand and "dash" it into the sanded mould. The clay was pressed into the mould with the hands and the excess clay removed from the top of the mould with a strike, which was a flat stick that had been soaking in water. This excess clay was returned to the clot moulder to be reformed . Sand was used to prevent the clay from sticking to the mould.
Single, double, 4 or 6 brick moulds were used. The single brick mould had an advantage in that a child could carry it to the drying area. Beech wood was the preferred material for the mould for it was claimed that the clay would not stick to it. The top of the mould was laminated with iron to prevent wear. The brick slid easily out of the mould because it was sanded and these bricks are referred to as "sand struck bricks". The process was also referred to as slop moulding.
The next person on the team was called an off-bearer. He would walk up to the moulding table, remove the filled mould and take it to a drying area on a pallet or barrow where it would be placed on a level bed of sand. He would then return the mould to the table and wet and sand it to receive the next brick.
The moulder would sand his wooden mould, and throw the lump of clay into the mould, so that it filled every corner. The excess clay would be cut away from the top with a wire bow. The mould could then be lifted up and the newly formed 'green' (unfired) brick lifted and turned out onto a hack barrow. This was a barrow on which bricks could be stacked and then wheeled to the drying area.
While even an 11 year old boy was useful in hauling the brick, it took an experienced Potter, Mason, or Brick Maker to mix the clay, sand, and water in the correct proportions and to construct the kiln for firing. The wet clay mixture was placed in wooden moulds by hand, scraped smooth then taken from the moulds and set out to dry in the sun. The moulded bricks were stacked in a herring bone pattern to dry in the air and the sun. The moulded bricks were 1st left to dry for 2 days at which time they were turned over to facilitate uniform drying and prevent warping. During this time tools called dressers or clappers were used by "edgers" to to straighten the bricks and obtain a smooth surface. After 4 days of dry hot weather the bricks were sufficiently hard to allow them to be stacked on end in a herringbone pattern with a finger's width between them to allow further drying. This area was called a hack or a hackstead and the bricks were covered under roof or with straw to protect them from the rain or harsh sun. After 2 weeks the bricks were ready to be burned.
After drying, the bricks were stacked for burning. This temporary kiln, known as a clamp consisted of several walls of rows bricks built parallel to each other, each about 3 bricks in thickness. At a height of about 2 ft the walls were joined by corbeling courses into one large stack with small air spaces between the bricks. The stack could be built up to a height of 8 to 10 feet. If fired bricks were on hand they were used to construct the outer walls of the kiln and the surface was daubed with mud to contain the heat. If no fired bricks were available the kiln was constructed entirely of green or raw bricks which were stacked in such a way as to act as their own kiln. These kilns were called clamps or scove kilns. Wood and coal were used for fuel.
Even after drying in air the green bricks contained 9-15% water. For this reason the fires were kept low for 24-48 hours to finish the drying process and during this time steam could be seen coming from the top of the kiln. This was called "water smoke". Once the gases cleared this was the sign to increase the intensity of the fires. If it was done too soon the steam created in the bricks would cause them to explode. Intense fires were maintained in the fire holes around the clock for a week until temperatures of 1800ºF were reached. The knowledge and experience of the brickmaker dictated when the fireholes would be bricked over and the heat was allowed to slowly dissipate over another week.
The clamp kiln is encased in already fired bricks. This form of firing was very uneven - the bricks towards the outside being underburnt, with others being overfired. The bricks were sorted, and sold at different prices, depending on their quality. Permanent kilns could take different forms, with updraft kilns channelling hot air upwards, and downdraft kilns pushing the air up and around the kiln. Towards the end of the century the firing process became more mechanised with the use of continuously firing kilns, and the bricks being pressed and shaped by machine.
When the kiln was disassembled the sorting process began. If only raw bricks were used, the bricks from the outermost walls were kept to be burned again in the next kiln. Some bricks which were closest to the fire received a natural wood ash glaze from the sand that fell into the fires and became vaporized and deposited on the bricks. These bricks were used in the interior courses of the walls. Bricks that became severely over burned and cracked or warped were called clinkers and were occasionally used for garden walls or garden paths. The best bricks were chosen for use on the exterior walls of the building. Those that were only slightly underfired had a salmon colour and early bricklayers knew that the porosity of these bricks would help to insulate the structure and they were placed on the innermost courses of the wall. To protect the underfired bricks and mortar and to impart a uniform colour to the exterior wall surface a "Colour Wash" was applied. This consisted of glue sizing, pigment (iron oxide), and potash alum.
A fire of coal of wood was stared in the bottom of the clamp, with tunnels near the bottom serving as fireplaces. After the fires were started, the ends of the tunnels were blocked off. If correctly built, the temperature in the clamp reached 1800ºF mark needed to harden the bricks. The fires were built up gradually, then the heat maintained for several days. When the fires stopped burning, the clamp was allowed to cool for several days before disassembling. When the clamp was dismantled the bricks were sorted so that the hardest bricks could be used for the outer wall. The bricks varied widely in colour and quality due to impurities in the clay and sand and the brick's location in the clamp. The ends of the bricks which were closest to the fire were a darker colour than the other faces and could be used for accents in the finished wall. Several instances in which the brightest most attractive bricks were reserved for the front of the house, or for the area surrounding the main entrance. Because bricks are small and relatively light in weight, they must be made to overlap or bond with each other to make a strong wall.
In historic bricks houses, the inner and outer brick walls are most often bonded together in a pattern known as the Common Bond., in which there are 6 or 7 rows of stretchers (long faces of bricks) to 1 row of headers (brick ends. The Flemish Bond, in which headers and stretchers alternate in each course, is also found here. Occasionally, the front of the house is laid in a Flemish Bond, while the side and rear walls show the less-decorative, more-economical Common Bond. The mortar used in these historic buildings was a mixture of lime and sand.
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