Brick

• 1. Introduction

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  Brick, the humble rectangular block, was already underfoot at Tell Aswad before 7500 BC, making it one of the oldest manufactured building materials on earth. The first bricks were shaped from river mud and left to dry under the sun. No kiln, no glaze, no industry. Yet from that elemental beginning, brick would go on to pave the floors of Terracotta Army pits, rise into the arches of Roman aqueducts, and line the furnaces of the Industrial Revolution. How did a shaped lump of earth become the most widely used building unit in human history? And how did the craft of making one evolve from anonymous labourers treading clay underfoot in Ming dynasty China to machines capable of turning out 25,000 bricks a day in Victorian England? Those are the questions this documentary sets out to answer.

• 2. Mud Before Fire

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  The oldest bricks ever found, at Tell Aswad in the upper Tigris region and in southeast Anatolia close to Diyarbakir, date to before 7500 BC. They were shaped from clay-bearing mud and dried, not fired. Mudbrick construction was underway at Catalhoyuk by around 7400 BC, and by around 7200 BC, structures built from the same material had appeared at Jericho in the Jordan Valley. Those Jericho bricks were among the first with recorded dimensions: 400 by 150 by 100 millimetres. The South Asian inhabitants of Mehrgarh were building with air-dried mudbrick between 7000 and 3300 BC, making their region one of the longest-running users of the technology anywhere.

  Mudbrick is not simply inferior fired brick. It is a distinct material with its own logic. The ingredients are silt, clay, sand, gravel, and stone, mixed with binding agents like chopped straw, grasses, tree bark, or dung in a ratio of roughly one part straw to five parts earth. That ratio reduces shrinkage as the brick dries. Adding more clay could substitute for the straw, which prevented insects from breaking down the organic fibres over time. After mixing and fermenting for about a day, the paste is pressed into rectangular moulds and set out to dry. Each brick needs roughly three days per side, for a minimum of six days, with eight or nine days being the average before the bricks are ready to use. Unfired bricks are best suited to arid environments where the sun can do the work of a kiln.

• 3. Fire and Empire

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  Between 5000 and 4500 BC, Mesopotamia discovered the fired brick. The change was not merely technical. Fired brick opened the door to architecture on a monumental scale. By 604 BC, glazed fired bricks were being used in the Hanging Gardens of Babylon. Across the Indus Valley, a remarkable standardisation had taken hold: bricks from cities as far apart as Mohenjo-daro, Harappa, and Kalibangan all conformed to a 1:2:4 thickness-to-width-to-length ratio. The Great Bath at Mohenjo-daro, the fire altars of Kaalibangan, and the granary of Harappa all rose from this uniform stock. When the Indus civilisation began its decline at the start of the second millennium BC, Harappan migrants carried brickmaking knowledge eastward, feeding demand in cities like Pataliputra, Kausambi, and Ujjain.

  In China, fired bricks appeared at Chengtoushan, a walled settlement of the Daxi culture, around 4400 BC. Those early Chinese bricks were made from red clay, fired on all sides to above 600 degrees Celsius, and used as flooring. By 3300 BC, fired bricks were paving roads and serving as building foundations at the same site. Proper structural brick construction for erecting walls and vaults did not come until the third century BC, when baked bricks of regular shape began to be used for vaulting underground tombs. The oldest surviving brick building above ground in China is Songyue Pagoda, dated to 523 AD.

  Fired bricks were first mass-produced during construction of the tomb of China's first emperor, Qin Shi Huangdi. The floors of the three pits of the Terracotta Army were paved with an estimated 230,000 bricks, most of them measuring 28 by 14 by 7 centimetres, a 4:2:1 ratio. In Rome, standardised fired bricks were being produced at scale by the early first century CE. The Roman legions carried mobile kilns and stamped each brick with the seal of the legion. Their material survives in the Herculaneum gate of Pompeii and the baths of Caracalla.

• 4. Craft and the Kiln

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  The 17th-century encyclopaedic text Tiangong Kaiwu gave historian Timothy Brook a window into how brick was made in Ming dynasty China. The kilnmaster's role was irreducibly skilled: he had to keep the temperature inside the kiln at the level where clay shimmered with the colour of molten gold or silver, and he had to judge exactly when to quench the kiln with water to produce the right surface glaze. Everything else fell to anonymous labourers. They mixed clay and water, drove oxen over the mixture to trample it into a thick paste, scooped it into standardised wooden frames to produce bricks roughly 42 centimetres long, 20 centimetres wide, and 10 centimetres thick, smoothed the surfaces with a wire-strung bow, removed the bricks from their frames, stamped the fronts and backs with marks indicating origin and maker, loaded the kilns with fuel, stacked the bricks inside, removed them to cool while the kilns were still hot, and bundled them into pallets for transport. As Brook put it: it was hot, filthy work.

  The carpenter's manual Yingzao Fashi, published in 1103 during the Song dynasty, had already described brick production and glazing techniques in formal terms. The knowledge was codified, yet the labour remained intensely physical for centuries. The modern tunnel kiln changed the equation by firing bricks continuously as they moved through on conveyors or kiln cars, producing a more consistent result. The Bull's Trench Kiln, based on a design by British engineer W. Bull in the late 19th century, works differently: an oval or circular trench is dug and filled with unfired bricks stacked in an open lattice, and the firing zone rotates through the trench rather than the bricks moving at all. A crew of around half a dozen workers can fire 15,000-25,000 bricks a day using this method. Its key advantage is energy efficiency: fresh air flows first through recently burned bricks to pick up heat, then through the active burning zone, then through the green brick zone, pre-heating and drying the next batch before it reaches the fire.

• 5. The Industrial Turn

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  Production of bricks increased enormously with the onset of the Industrial Revolution and the rise of factory building in England. In London, bright red brick was chosen specifically to make buildings more visible in the heavy fog and to help prevent traffic accidents. Speed and economy made brick preferable to stone even in regions where stone was plentiful.

  The shift from hand-moulding to mechanised mass production played out across the first half of the 19th century. Richard A. Ver Valen of Haverstraw, New York, patented the first brick-making machine in 1852. Bradley and Craven Ltd followed in 1853 with their Stiff-Plastic Brickmaking Machine patent, going on to dominate the manufacture of brickmaking machinery. Henry Clayton, working at the Atlas Works in Middlesex, patented a machine in 1855 that could produce up to 25,000 bricks daily with minimal supervision. It attracted widespread attention after the South Eastern Railway Company adopted it for brick-making at their factory near Folkestone.

  By the end of the 19th century, the Hudson River region of New York State had become the world's largest brick manufacturing area. Some 130 brickyards lined the shores of the Hudson from Mechanicsville to Haverstraw, employing 8,000 people. At peak output, the region produced roughly 1 billion bricks a year, much of it shipped to New York City. That era of brick supremacy ran into its structural limit with the demand for tall office buildings at the turn of the 20th century. The Monadnock Building, completed in 1896 in Chicago, needed exceptionally thick walls to maintain the structural integrity of its 17 storeys. Steel and concrete were simply better suited to height, and brick retreated to small and medium-sized structures.

• 6. Material Varieties

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  Calcium-silicate bricks, also called sandlime or flintlime bricks, skip clay entirely. They bind lime with sand, quartz, crushed flint, or crushed siliceous rock in a ratio of roughly 1 part lime to 10 parts silicate material. After pressing into moulds, the bricks are cured in an autoclave for three to fourteen hours. The result is highly uniform, though the sharp edges require careful handling to avoid damage to both the brick and the bricklayer. This type is common in Sweden, Russia, and other post-Soviet countries, particularly in buildings constructed or renovated in the 1970s. A variant called fly ash brick, made using fly ash, lime, and gypsum through the FaL-G process, is widespread across South Asia.

  Concrete bricks are formed from dry, small-aggregate concrete, shaped in steel moulds by vibration and compaction, then cured with low-pressure steam rather than fire. They are manufactured in a wide range of shapes, sizes, and surface treatments, and some are designed to simulate the appearance of clay bricks. Concrete bricks shrink as they cure, meaning movement joints are needed every 5 to 6 metres. Compressed earth blocks represent a third route: local soil, slightly moistened, pressed under a mechanical hydraulic or manual lever press, sometimes with a small amount of cement binder added for stability.

  The colour of fired clay bricks is not arbitrary. A high iron content produces pink bricks, while higher lime content gives white or yellow ones. As firing temperature rises, the colour moves through dark red, purple, and then to brown or grey at around 1300 degrees Celsius. Some bricks carry their origin in their name: London stock brick, Cream City brick from Milwaukee, Chicago common brick in buff yellow or salmon pink, and Staffordshire blue brick from England. The Colombian architect Rogelio Salmona became known specifically for his extensive use of red bricks combined with natural shapes like spirals, radial geometry, and curves.

• 7. Dimensions and Limits

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  The optimal size of a brick is set by human anatomy. A brick must be small enough and light enough to be picked up with one hand, leaving the other free for the trowel. The practical width limit is around 100 millimetres, the span a hand can comfortably bridge between thumb and fingers. In England, the length and width of a common brick were regulated by statute from 1625. The modern standard in the United Kingdom, in place since 1965, is 215 by 102.5 by 65 millimetres; with a 10-millimetre mortar joint, each brick occupies a nominal 225 by 112.5 by 75 millimetres. The United States modular brick runs 194 by 92 by 57 millimetres, and the 2:1 ratio means corners can turn without cutting.

  A historically documented illustration of the consequences of getting brick size wrong comes from Gdansk. The Green Gate, built in 1571 using imported Dutch brick, was notoriously cold and drafty because the Dutch brick was too small for the colder climate of Gdansk. Larger bricks make thicker walls, and thicker walls insulate better; that correlation once dictated regional brick sizes across Europe.

  Brick masonry has a specific vulnerability that became undeniable in the 20th century. The San Francisco earthquake of 1906 and the 1933 Long Beach earthquake exposed the weakness of unreinforced brick in seismic zones: the mortar cracks and the bricks lose their binding. Steel reinforcement can hold masonry together during earthquakes, and retrofitting older unreinforced structures has been mandated in many jurisdictions. However, the steel rebar inside reinforced brick is subject to rusting, which eventually compromises structural integrity, creating a trade-off between earthquake safety and the building's expected lifespan. The Monadnock Building's need for exceptionally thick walls at 17 storeys, paired with this seismic fragility, points toward why brick's role in construction shifted decisively after a 9,000-year run.