Introduction to Historic Brickmaking
The first step in making bricks was to find a suitable supply of the main ingredient, clay.
Slaves excavated the clay by digging an open clay pit. In Columbia, the clay pit that slaves
likely used to make bricks was located on a square plot bounded on the north by Greene Street,
the south by Devine Street, and the east by Williams Street.
Slaves took the moist mineral clay and packed it into a mold usually made of wood and sometimes
lined with copper. The size of these molds could vary based on the type of clay slaves were using.
Bricks that were constructed of a stronger clay material would often shrink during the firing
process, so slaves would cast the bricks in a mold slightly larger than the desired size of the
brick in order to accommodate for this shrinkage. Slaves then left the resulting brick molds on
the ground to air dry. After the brick molds were dry, slaves would remove the bricks from their
mold and place them into a kiln or fire pit, which would often heat up to 2000 degrees Fahrenheit.
Since up to 20,000 bricks could be placed into the kiln at once, this process, known as firing,
produced bricks of varying quality and composition. The result was that bricks nearest to the
fire became very hard, sometimes brittle, while those that were furthest from the fire often
maintained a soft core. After firing at this temperature for a few days, slaves would gradually
decrease the temperature of the kiln by opening air holes, which allowed the bricks to cool.