Brickmaking

c. 1850 AD

 

There are five steps needed to make bricks.

The first step is called WINNING, or mining the clay.

Because the steam shovel was not invented until 1879 early brickmakers had to dig for the clay on site with hand shovels. This was done in autumn. The early brickmaker chose his clay by it's color 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.  

The second step is PREPARATION of the clay

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. (below)

The clay was removed from the soaking pit or pug mill by a temperer who delivered it to the moulding table.

 The third step is MOULDING.

The assistant brick mouder 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.

Moulding table shown in Dobson's Book

  
Mould (top) and stockboard (below) of the kind used for making bricks in the nineteen century

Single, double, four or six 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 prefered 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 recieve the next brick.

Barrow for twenty-six bricks illustrated by Dobson

   The fourth step is DRYING

 

The moulded bricks were stacked in a herring bone pattern to dry in the air and the sun. The moulded bricks were first left to dry for two 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 four 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 futher 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 two weeks the bricks were ready to be burned. (contest)

The fifth step is BURNING
 

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 availible 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 1800 degrees F 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.

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 recieved 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 color 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.

According to representatives from Virginia Limeworks, to protect the underfired bricks and mortar and to impart a uniform color to the exterior wall surface a "Color Wash" was applied. This consisted of glue sizing, pigment (iron oxide), and potash alum as illustrated below. The mortar joints were then painted white.

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