The Enduring Legacy of Brick: History, Production, and Future Prospects

---

Background

Brick is a timeless building material that combines durability, fire resistance, and thermal retention. Small, typically 4 inches wide and twice as long, bricks fit snugly into tight spaces and curved designs, reducing the need for costly structural interventions.

Used for more than 5,000 years, the first bricks emerged in the fertile lands between the Tigris and Euphrates—modern-day Iraq. Early sun‑baked bricks were fragile and unsuitable for exterior use, but the Babylonians pioneered kiln firing, producing the robust bricks that supported their iconic tower‑temples.

Brickmaking spread from the Middle East to Egypt, Persia, and India. While the Greeks favored stone, Roman engineers employed bricks extensively; after Rome’s fall, European production waned until the 12th century when Dutch artisans revived the craft, exporting bricks to England. In the Americas, brick began to appear in the 16th century, but Dutch expertise remained unmatched.

Prior to the mid‑1800s, bricks were fired in small, inefficient open clamps—bricks baked over weeks beneath layers of dirt and used bricks. The 1865 invention of the Hoffmann kiln in Germany revolutionized production: a series of chambers pre‑heat, burn, and cool bricks automatically, enabling high‑volume output.

Modern advances focus on shape uniformity, weight reduction, and accelerated firing. Press‑formed bricks feature a characteristic “frog” depression; extruded bricks contain perforations that increase surface area, both cutting weight without compromising strength.

Despite production improvements, the brick market has stagnated. Brick still commands the largest share of the opaque materials market for commercial construction and remains a favored siding material in the residential sector. However, alternatives such as wood, stucco, aluminum, plaster, and vinyl offer up to 50 % lower costs and built‑in insulation. Yet, these materials can be 1.75 times pricier than brick and often require more maintenance. Competing products—including precast concrete panels, glass, stone, artificial stone, and concrete masonry—benefit from recent manufacturing advances that make them increasingly attractive to builders. According to the U.S. Industrial Outlook, brick’s share as a siding material in single‑family homes fell from 26 % in 1984 to 17 % in 1989.

Raw Materials

Brick’s core composition is natural clay minerals—kaolin and shale—augmented with small amounts of manganese, barium, and other additives to achieve desired hues and enhance chemical resistance. Barium carbonate is often incorporated to improve durability against environmental exposure. Additives such as paper mill by‑products, ammonium compounds, wetting agents, flocculants, and deflocculants further refine texture and flow. Where necessary, sand or grog (pre‑fired brick fragments) is blended to achieve optimal particle size.

Coating processes determine final color and surface finish. Sand is mixed with colorants; sometimes a flux or frit (glass with colorants) is added to lower the melting point, creating a bonded glaze. Alternative binders—including graded fired and unfired brick, nepheline syenite, and graded aggregate—are also employed.

The Manufacturing Process

The journey from raw material to finished brick begins with crushing and grinding in a separator and jaw crusher. The resulting blend is screened for particle size, then directed to one of three shaping methods: extrusion, molding, or pressing—extrusion being the most common due to its versatility.

Grinding, Sizing, and Combining Raw Materials

• Raw ingredients are conveyed to a separator that removes oversize particles. A jaw crusher further reduces size. Oversized material is redirected to a hammermill for fine pulverization, and vibrating screens ensure uniform particle distribution before storage.

Extrusion

• Extrusion is the predominant brick‑forming technique. Pulverized clay and water enter a pug mill where rotating knives fold the mixture into a pliable mass. The mass is then air‑depleted in a vacuum chamber to prevent cracking, compressed in a high‑pressure cylinder, and extruded through a die that imparts the desired cross‑section. The extruded column, or “pug,” is cut to length, producing uniform bricks with characteristic top depressions.

Molding and Pressing

• Molding shapes wet clay in a wooden box, often lined with sand to create texture and aid release. Pressing compacts low‑water clay with a steel plunger, yielding bricks with sharper edges and a pronounced frog. Both methods complement extrusion by accommodating specialty shapes and higher‑grade finishes.

Chamfering the Brick

• Chamfering machines indent a furrow into bricks—essential for paving applications—while they are extruded. With rollers and optional wire cutters, these machines can produce up to 20,000 units per hour.

Coating

• The coating method depends on material hardness. Soft bricks receive a continuous vibrating feeder; textured bricks are brushed or rolled on; hard bricks use pressure rollers or compressed air; extremely hard bricks may require sandblasting.

Drying

• Pre‑firing drying removes moisture that would otherwise cause cracking. Tunnel dryers move bricks through humidity‑controlled zones with hot air, while automatic chamber dryers—common in Europe—use rail‑mounted transfer cars to feed bricks onto racks for staged drying.

Firing

• After drying, bricks are automatically loaded onto cars and fired in tunnel kilns. The cars traverse temperature‑controlled zones at rates tailored to the material. Gas fuels dominate U.S. kilns, though solid fuels such as sawdust and coal account for a third of production. Modern kiln designs—shorter, wider, and equipped with high‑velocity, long‑flame burners—improve temperature uniformity and reduce fuel consumption.

Setting and Packaging

• Once cooled, the dehacking process automatically stacks, wraps with steel bands, and pads bricks with plastic corner protectors. Automated setting machines can handle over 18,000 bricks per hour, rotating each 180° to ensure uniformity. Packaged bricks are then shipped via boom trucks to job sites.

Quality Control

Modern brick manufacturers adopt total quality management and statistical process controls, setting real‑time limits for parameters like drying and firing temperatures. These controls minimize defects and maximize yield.

Bricks must meet ASTM standards for dimensions, density, mechanical strength, and freeze‑thaw durability. Current freeze‑thaw tests inadequately mimic real‑world conditions; research continues to refine predictive field‑performance tests.

Efflorescence—surface discoloration caused by salt deposits—remains a challenge. While laboratory tests can certify bricks, field failures often result from design or construction issues. Consequently, many companies develop proprietary in‑house tests and pursue more reliable industry standards.

The Future

Annual brick consumption currently averages 7–9 billion units—roughly half the 15 billion used in the early 1900s. The industry seeks to broaden market share through quality enhancements, productivity gains, and fuel‑efficiency improvements. By 2025, solar‑powered kilns may become viable, further reducing emissions.

Environmental regulations—particularly those governing fluorine emissions—pose significant compliance costs. Fluorine, a byproduct of firing, poses health risks; the EPA sets strict exposure limits. While scrubbers mitigate emissions, they are expensive. The U.S. industry is actively developing cost‑effective monitoring techniques and negotiating lower limits to avoid a potential industry contraction.