at Colonial Williamsburg, tourists can process the clay used for making bricks
at Colonial Williamsburg, tourists can process the clay used for making bricks
clay formed into bricks must dry before being assembled into a kiln and baked
Making brick is an ancient art. Some of the oldest discovered to date have been excavated at the town of Jericho in modern Turkey. Bricks there are 9,000 years old, dating back to 7,000 BCE.
Those bricks were made from mud and dried in the sun, similar to the construction of adobe houses. Bricking that were intentionally fired to metamorphose the clay and make it more waterproof have been found in China, and date back to 4000-3000 BCE. However, the Native Americans in Virginia made only pottery. They heated clay in fires fueled by wood to manufacture cooking vesssels, but never fired clay at a high enough temperature (2,000°F) to make bricks.
Bricks are a human-made metamorphic rock. The raw material is clay, a sedimentary layer formed of particles that decomposed from feldspar and other bedrock minerals and washed downstream to an accumulation site. There is clay throughout the entire Coastal Plain, and it is common in stream valleys within all other physiographic provinces.
High quality clay for pottery and bricks contains no organic material or pebbles. Pottery makers add a selected amount of sand or crushed shells to their clay as temper. The sand/shell particles have a different shape than clay particles. Adding additional material allows the clay to release moisture as it heats; otherwise, the pottery would crack in the fire due to steam pressure.
Bricks are made each year at Colonial Williamsburg. Interpreters there "knead" the clay to remove large non-clay particles, which in the 2,000°F heat would expand and crack the brick. Once hands and feet have processed the clay to create a conbsistent mixture, people making bricks by hand place the mud in a mold that defines the shape of the final product. Most molds are rectangular, but some include rounded edges to make the coping bricks on top of walls and used as decorative features.
bricks are made from clay that is shaped in a mold, then dried before firing
Source: Mads Bolton, Historic Trades and Skills of Colonial Williamsburg (June 21, 2024 Facebook post)
In colonial Virginia, each brickmaker had his own molds; they were not standardized with one size throughout the colony. Fine sand coated the interior of each mold when the mud was slapped inside and then leveled at the top. Without the sand, the mud would stick inside the mold. Workers would dump the soft mud brick out of the mold and place it in the sun, where it would dry for at least several weeks. A tarp or wooden roof helped keep the bricks out of the rain, allowing them to dry before being fired in a kiln or "clampe."
Bricks were made from mud during the Summer so they would dry. By September, all the bricks to be fired were stacked. After crops had been harvested in the Fall, additional labor would be available for firing a kiln in November.
The brickmaker had his labor crew stack several thousand mud bricks to make a kiln. A series of tunnels were created at the bottom of the stack as bricks were placed together carefully to create a pile 10-15 feet high. The tunnels were designed so the laborers could place wood inside them. The wood was lit, and a fire would burn for 4-5 days within the pile.
dried mud bricks are stacked to create a kiln, inside which the bricks will be heated to 2,000°F
Source: Mads Bolton, Historic Trades and Skills of Colonial Williamsburg (September 18, 2024 and October 18, 2024 Facebook posts)
Within the pile, bricks were stacked close to each other but not touching on the sides. The spacing allowed heat to rise from the wood fires in the tunnels, gradually raising the temperature within the kiln. The exterior of the kiln was lined with old bricks which were covered with mud, and metal covers were used to control the amount of air that could enter the tunnels at the sides of the kiln. Except for the tunnels and the top of the stack of mud bricks, the exterior of the kiln was insulated and made to be air-tight.
the exterior of a brick kiln was insulated with old brick and mud, with bricks to be fired stacked inside
Source: Mads Bolton, Historic Trades and Skills of Colonial Williamsburg (November 18, 2024 Facebook post)
The brickmaker's special skill was in controlling the temperature inside the kiln. It not heated enough, the final product would be soft salmon-colored bricks. They would crumble when exposed to rain. If heated too hot, mud bricks would melt together and create a pile of useless metamorphosed clay.
Small sticks of wood were ignited in the tunnels to start the firing of the kiln. For the first few days, those tunnels were left open all day and night. Larger pieces of firewood were added gradually as the fires became self-sustaining underneath the stacked bricks. Hot coals were pushed into the center at the bottom of the pile. The goal was to heat all the bricks evenly as the temperature inside the entire kiln slowly increased.
firewood shoved inside the tunnels heats the bricks stacked within the kiln
Source: Mads Bolton, Historic Trades and Skills of Colonial Williamsburg (November 23, 2024 Facebook post)
At the start of the firing, a tarp above the top of the stack would be used to keep the mud bricks dry during a rainstorm. Later in the process, rising heat from within the kiln made a covering unnecessary - and unrealistic, since any cover would burn unless it was raised far above the kiln.
After about three days, the tunnel openings were closed except when more firewood was added. Heating the kiln required wood to be added about every hour, all day and night. A cord of wood was burned for each 1,000 bricks manufactured.
The bottom of the stack, where the wood was burning, was hottest. When it first reached 2,000°F, the middle would be 1,800°F and the top would be around 1,600°F.
Hot air rising through the stack slowly forced moisture out of the individual bricks. Clay particles dried and then vitrified, melting together to create a water-resistant metamorphic brick. Iron in the clay oxidized, creating the red color. Potash in the wood would glaze the exterior of the bricks near the tunnels, adding a black color and making then more watertight.
The brickmaker used several clues to determine when to stop firing the kiln. The color of the bricks glowing different shades of yellow within the stack, as seen through the tunnels, indicated if the desired temperature had been reached. The bricks would shrink as the water was boiled away, and the top of the stack would slump slightly in response. Throughout the firing, the brickmaker would climb a ladder to view the top, If the slumping was more pronounced in one part of the stack, wood would be added at one part of a tunnel or air flow would be modified to even out the distribution of heat.
When the bricks had been cooked sufficiently, the coverings around the tunnel would be sealed with clay and the pile left to cool. After about a week, the mud and exterior bricks would be stripped off the sides of the kiln and the newly-fired bricks could be unstacked.
A wealthy person, church vestry, or government agency would contract with a brickmaker to produce enough bricks for each structure. The brickmaker, typically someone who moved from project to project as contracts became available, would acquire a crew of enslaved and free blacks to perform the tedious labor tasks. A hearth and fireplace would require around ___ bricks. The George Wythe House in Williamsburg required 250,000 bricks, and the Governor's Palace used _____ bricks.
Machinery to manufacture bricks was created in 1885. Mass production facilitated construction of houses, commercial buildings, and industrial plants in cities across the United States. Modern tall buildings rely upon an internal steel frame for support and use bricks for exterior facing, but there are still 10,000,000 bricks in the Empire State Building in New York City. 1
after several days, tunnels within the brick kiln are fueled hourly and then sealed
wood is added to the kiln night and day for about five days
prior to the Civil War, enslaved workers unstacked the fired bricks from the kiln
Source: Colonial Williamnsburg, Meet the Brickmakers!
Source: Townsends, The Ancient Art Of Brickmaking - Impervious Building Blocks Handmade From The Earth
Insider, How Bricks Are Made