If you examine local brickwork of the 18th and 19th centuries you will see a small number of bricks that have black ends, apparently glazed. This black glazing is not intentional. The “black-heads” were those bricks directly exposed to the kiln fires. Called black-end or black-head bricks they were usually considered seconds and were often placed away from the street side of houses or hidden under pent eaves or such or used on utility buildings like smoke houses. Sometimes in the early days, though, they were used as a decorative element.
The black-heads were good, hard bricks most suitable for the outside skin of the wall as they were well vitrified. Next to the black-heads, the hardest bricks from the kiln were called “red stretchers” and were, indeed, a red color. These, too, were close to the highest heat and were used on the outside of the walls since they resisted weathering. The softer salmon brick, true to their name, were orange and not red since being farthest from the kiln fire, their clay was just bisqued and not fully vitrified. Most walls were three bricks thick and the salmon bricks went on the wall’s inside, away from the weather.
When the kiln was opened after firing, grading the brick was a matter of judgment. Red stretchers being the best and most expensive, it’s easy to see how some cheaper salmon brick made their way into the outside skins of barns and houses and in time deteriorated as anyone who has an old brick structure knows.
In any case, the economy of firing brick kilns favored size. The kilns were built with perhaps 20,000 green bricks and the larger may have many thousands more. Building the brick kiln pile was a highly skilled craft. The rectangular pile may have been forty or more feet long and ten or more feet high with fire pits every four to six feet. The fire pits were open on both sides so the fuel, wood and later coal, could be thrown in.
Firing took about seven days and was also a skilled craft. By watching the color of the gases and fire filtering up through the top of the pile, the burner knew whether to increase or decrease heat in a particular fire pit. He could judge when one area was “done” by the amount of shrinkage or settling of that part of the pile; since clay shrinks seven to ten percent when it is fired. (Incidentally, in today’s nomenclature clay products are “fired” or in the case of bricks “burned” not baked; cakes are baked, clay is fired).
All bricks made near Philadelphia before about 1830 were burned with wood, and it took a prodigious quantity of wood. One source suggested that the burner needed forty or fifty cords on hand to burn a large kiln of brick!
Before about 1800 there were millions of bricks (and that’s not a figure of speech) used in Philadelphia County. However, local brick building slowed to a crawl (my observation) in the early decades of the nineteenth century. At that time there was an acute firewood shortage in Philadelphia and environs.
Coal became available only after the Schuylkill Canal was opened about 1830, followed a few decades later with the coming of the railroads. Brick kilns were then fired with coal, and brick became the material of choice for much new construction. There was a brick building boom for the rest of the 19th century.
Finally, from time to time researchers come across the term “ballast bricks.”
Ships needed to be freighted with a minimum amount of weight or they would bob around like corks. The idea emerged that 18th century ships that were freighted with timber, grain and such from Philadelphia to England returned with bricks as ballast. Research, however, shows that this is not true. The incoming ships were freighted with a cornucopia of goods of every nature, but not building bricks.
There are some slight references to imported bricks during the 18th century in the Philadelphia press, but these may be the square glazed bricks used as hearths and not building brick. But the principal reason bricks were not imported was that in the year 1700, 1000 red bricks sold in London for about 15 shillings and in Philadelphia for 6 shillings. If anything, they would have gone the other way.
The 1893 book “Pottery and Porcelain of the United States” notes: “The belief that all bricks which were used in the construction of houses in this country previous to the middle of the eighteenth century were imported from Europe is widespread but erroneous. … That building bricks were extensively manufactured here previous to 1753 is indicated by a statement of Lewis Evans of Philadelphia, who wrote to a friend in England in that year: ‘the greatest vein of Clay for Bricks and Pottery. Begins near Trenton falls, and extends a mile or two in Breadth on the Pennsylvania side of the river to Christine; then it crosses the river and goes to Salem. ‘The whole world cannot afford better bricks than our town is built of.’ “
This same source states that black-head bricks were produced in wood fired and coal fired kilns : “Those which came in direct contact with the wood-fire in the kiln were blackened and partially vitrified on the exposed ends; while the opposite extremities, which were farthest from the heat, were only partially baked, and consequently too soft for external use. The bricks that were uniformly surrounded by heat came out red. To utilize all of the bricks produced, the black ends of the former were laid outward in the wall, thus combining utility with ornamentation.”
Another source copyrighted in 1900 notes: “Bricks which became varnished black in wood firing were, however, also used in architectural decorations.”
