brick. Solid, hollow, or indented building element, usually rectangular, but also other shapes for special purposes, manufactured from clay, concrete, sand, and lime, or other materials, formed in a mould, then burnt, set, or cured. Its advantage over masonry lies in the ease of mass-producing the bricks to standard sizes in the moulds, and in the fact that it can be lifted and laid using one hand, leaving the other free for holding the trowel for manipulation of the mortar. Terms to describe bricks include:Accrington: see engineering brick below;air-brick: with regular perforations to allow air to pass through a wall;angle-brick: see dogleg;arch-brick, also called tapered headers or tapered stretchers: special brick tapered along its length to serve as a voussoir in an arch;bat: half, three-quarter, large-bevelled, or small-bevelled part of a brick greater than a quarter-brick, with the cut made across its width. It is used as an alternative to a closer in bonding to make up the dimensions in the courses of a wall;bird's mouth: with a wide angular notch in one of the header faces;brick tile: see mathematical tile below;brindle: attractive brown-purple brick, or bricks discoloured with stripes;bullnose: with a rounded edge instead of an arris (single bullnose, used where arrises are vulnerable) or with two rounded edges (double bullnose, for copings);calcium silicate brick: brick, also called flint-lime or sand-lime brick made from sand or crushed flint mixed with hydrated lime, then pressed into a mould and permitted to harden, usually in an autoclave;cant brick: moulded brick with one corner (single-cant) or two corners (double-cant) cut off with a diagonal;capping brick: shaped brick laid on edge on the top of a wall but not projecting beyond its faces. It can be a half-round, bull-nosed, saddleback (triangular), or segmental type;clinker: 1. brick the surface of which is vitrified by exposure to intense heat in the kiln or clamp.2. Hard pale brick made in The Netherlands, and used for paving; circular brick: curved on plan, for curved walls;closer: brick cut or moulded lengthways, exposing an uncut stretcher-face and a half-header, used to close the course at the return of the wall or at an opening in it, and to keep the bond. Closers are of various types: bevelled closer (j)— with splayed stretcher-face, a half-header at one end, and a whole header at the other, king-closer (i )—three-quarter bat with concealed splayed corner, and exposed half-header, mitred closer (k)—with one end sharply splayed and the header-face removed, leaving a half or three-quarter stretcher, used where adjacent bricks join at an angle, and queen-closer (usually next to the first brick in a header-course, consisting of half a brick half queen-closer (g)—or a quarter brick quarter queen-closer (h));closure: brick slip, smaller than a bat, used with a header to make up the full width of an early eleven-inch cavity-wall, where the two leaves were to be bonded, as in Loudon's hollow wall; common brick: cheap bricks used where appearance or strength are not critical;compass brick: also radial or radiating brick, it is tapered for use in arches, circular windows, or patterns;concrete brick: moulded brick made from cement, sand, and crushed stone, etc., used instead of common bricks;coping bricks: like a capping-brick, used for copings, with bullnose, canted, saddle-back, segmental, or semicircular tops, laid on-edge, and made so that the ends project beyond the face of the wall to throw water clear of it;Cossey white: very pale gault brick from Costessey, Norfolk, common in Norwich and environs, around 1830;course: horizontal layer or row of bricks;cownose: semicircular at one end only;cut and rubbed: brick cut to shape with a bolster then rubbed to a fine finish with a rubber brick;cutter: brick made from natural or mixed sandy loams (of uniform texture). When burnt they can be cut and rubbed to precise shapes;dogleg: angle-brick (o) used to ensure a good bond at quoins which are not right angles. A better job than mitred closers;dry-dipped enamelled brick: moulded, dried, burnt, cooled, coloured, glazed, and reburnt biscuitware;Dutch clinker: small yellowish brick often found in East-Anglian walls and pavements, called klinkart;engineering brick: very dense, durable, strong, and water-resistant, used for bridges, piers, sewers, and other engineering construction. The commonest types are Accringtons (bright orange-red, pressed, and smooth), Hunzikers (crushed flint and lime), Southwaters (pressed and wire-cut), and Staffordshire Blues (blue, wire-cut, and handmade, often used for plinths, as damp-proof courses, and for copings);facing: superior brick selected to be seen on the exposed face of a wall;flare: see vitrified brick;Flemish brick: thin brick imported from Flanders or The Netherlands or made to imitate this type;Fletton: made from Knotts clay found near Peterborough, Cambridgeshire, containing a large proportion of finely distributed combustible matter, with a resulting economy of fuel when being fired. A mass-produced common brick;gault: dense brick made from limy or calcareous clay-beds found between the upper and lower greensands and containing sufficient chalk to render the brick pale yellow or white when burnt, often with bluish tinges;glass brick: square glass block, unlike the shape of normal bricks, hollow or solid;glazed brick: usually of fireclay or shale, and accurate in size and shape, with exceptionally straight arrises, it is waterproof, enamelled, or salt-glazed. Useful for dados, plinths, and other surfaces requiring to be kept clean, or for light-wells where good qualities of clean, reflective surfaces are needed;header (a): laid with its short face exposed;Hitch brick: see rat-trap bond below;hollow brick: clay walling-block, larger than a true brick, useful for quickness of construction and properties of insulation;Hunziker: see engineering brick above;klinkart: see Dutch clinker above;London stock: yellowish-brown stock-brick made from London clay, often with the admixture of clinker from the coal used in previous firings, giving the finished brick dark spots with attractive patches of blue and red;malm: almost white brick made from marly (limy or calcareous) clay to which chalk is added, common in Cambs., Lincs., and Suffolk;mathematical tile: also called brick tile or wall tile, a tile with one face moulded to resemble the appearance and dimensions of a brick. It was laid in mortar and nailed to battens on a rough wall or timber-frame, then pointed so that the finished work looked like brickwork (see mathematical tile);multi-coloured brick: known as a multi, used for facing work, it has faces attractively coloured with bright red, dark red, blue, yellow, etc., and is most satisfactory with white pointing;perforated brick: has several small vertical cylinders of clay taken out from its core, leaving the faces indistinguishable from solid bricks;Pether's patent moulded brick: pale buff moulded brick with very sharp detail much used in C19, notably by Butterfield (e.g. at St Augustine's, Queen's Gate, London), and in countless Victorian terraces as lintels and string-courses;pistol-brick: used to form a smooth curve between wall and floor, especially where good hygiene is necessary and there is regular washing out;plinth bricks: usually moulded or splayed at the top;purpose-made brick: special brick for unusual or non-standard work;rubber: also known as a cutter, coloured soft red, white, or buff, it is formed from clean clay containing a lot of sand, moulded, then baked (not burnt). It is carved, cut, or rubbed with ease, and used for gauged arches, etc., with fine joints of lime-putty;sand-faced: with sand sprinkled on the clay before firing. Used to enhance the appearance of inferior clays (e.g. Flettons) and usually applied to one stretcher-and one header-face only;sand-lime: see calcium silicate above. It is usually employed in internal or below-ground work;shaped brick: any type of brick other than a normal rectangular unit, such as a pistol-brick;slip: small closure (p), or piece of brick smaller than a bat;snapped header: broken in half and laid so that its short face only appears in the wall-surface, suggesting a wall thicker than half a brick wide, so deceptive in terms of structural stability;soldier: with its stretcher-face set vertically;Southwater: see engineering brick above;special: made specially for a job (purpose-made), or a standard shaped brick;splay (l, m): with a bevelled top, used for plinths or cills;Staffordshire: see engineering brick above;stock brick: originally hand-made on a stock-board, but now machine-moulded. The term is also applied to any characteristic local facing-brick;stretcher (a): laid so that its longest face is exposed;vitrified brick: also a flare, it is often a very dark-blue or blue-black colour, usually with a shiny, glazed surface brought about by extremely high temperatures during firing, and is frequently found, often snapped, in walls forming chequer-board, diaper, lettered, or numerical designs; andwire-cut: formed by extruding clay through a rectangular die from the end of which individual bricks are cut off mechanically by serrated wires.

Terms associated with bricks or brickwork are:arris: sharp edge between two adjacent brick faces;bed: lower surface. A bed-joint is the horizontal mortar joint;cogging: as dog-tooth;course: complete horizontal layer of bricks— a brick-on-edge course has bricks laid on their stretcher-faces, a brick-on-end or soldier course is one of bricks laid on their header-faces, the stretcher-faces being then vertical, a heading or header course consists of headers, and a stretching or stretcher-course of stretchers;dentilation: alternate projecting headers, also called toothing, to carry a projecting course or cornice. See dog-tooth below;dog-tooth: also hound's tooth or mouse-tooth, it is a course of projecting bricks laid diagonally to carry a projecting course or cornice, giving a jagged saw-tooth effect, called cogging, achieved by the exposure of one corner. It is an alternative to dentilation;face: exposed surface;fair-faced: unplastered brickwork, usually withflat or flush joints, as used for internal walls, whether painted or not;frog: indentation or kick on the bed or the uppermost surface (b) or both—one-frog bricks laid with frog down save weight, work, and mortar, but they are usually laid frog up so that mortar fills the frog to ensure that the wall is strong;gauged: fine, precise brickwork, as in an arch of soft rubbers, often a bright red or creamy colour contrasting with the rest of the wall, used around window-and door-openings and for arches;indentation: see toothing;lap: horizontal distance between a vertical joint in one course and the joint in the course above or below it;leaf: thin brick wall forming part of a cavity-wall. There is an inner and outer leaf on either side of the cavity;nogging: brick infill panel in timber-framed construction;perpend: vertical line through superimposed vertical joints;quoin: external angle of a wall;sinking: see toothing;stopped end: also closed end, a square end of a wall the same thickness as that wall, finished with the aid of closers;toothing: dentilation, or projections of alternate courses at the end of a wall to provide a bond for a later addition, leaving indentation or sinking in each alternate course. Dentilation is also used in a different sense, as part of a cornice support (see above).

Brick bonds (the patterns formed by arranging the courses with bricks overlapping the joints to provide a sound structure) are many and varied, and are often confused. The list below is an attempt to establish descriptions of the commonest types:American bond: US term for a type of English garden-wall bond, but with a course of headers to every five or six courses of stretchers;American with Flemish bond: see Flemish stretcher bond;basket-weave: three soldiers alternating with three stretchers in squares with no bond, forming a chequerboard pattern;bastard bond: see header bondblock bond: US term for Flemish bond or common bond;block bonding (a): several courses of brick used to join one wall or part of a wall to another, e.g. where facing-bricks are bonded to common bricks of different sizes. The several courses may give the effect of quoins where they interlock with the different brickwork;chequered bond: bond formed of e.g. Flemish bond in which the headers are vitrified (a darker colour than the rest, and glazed), giving a regular chequered pattern. Flint or other materials may be used instead of vitrified headers to give the same effect;Chinese bond: see rat-trap bond;common bond: see English garden-wall bond;Dearne's bond (b): variation on English bond where stretcher courses are bedded on edge (i.e. on their face) with a cavity between, the header courses laid normally on their beds, bonding the leaves together, and saving bricks by a slight gain in height for every course of stretchers. Dearne's bond is often confused with rat-trap or Silverlock's bond. Dearne (or Dearn) also designed a bond with a course of headers, then a course of stretchers cut along their lengths giving a final appearance of ordinary English bond, but leaving unseen continuous cavities between the stretchers that could be heated (e.g. by connecting them from a stove to a flue) for use in conservatories;diaper: bonding involving the creation of patterns using bricks of a different colour set in the wall, such as vitrified headers, forming diamond, square, lozenge, and other designs;Dutch bond: also staggered Flemish bond, it is a variation on Flemish bond, with alternate headers and stretchers in each course, the courses being moved half a header on each course to left or right, giving a zig-zag effect called staggered Flemish in the USA. Another type of Dutch bond is actually a modification of English bond, and consists of alternate rows of headers and stretchers, but each stretcher-course begins at the quoin with a three-quarter bat and every alternate stretcher-course has a header placed next to the quoin three-quarter bat, causing the stretchers to break joint in alternate courses, the quoin three-quarter bats rendering the queen-closers of normal English bond redundant;English bond (d): strong bond of alternate courses of headers and stretchers;English cross-bond (e): also St Andrew's bond, it is similar to English bond, with alternate rows of stretchers and headers, and queen-closers next to the quoin-headers. Each alternate stretcher-course is moved half a stretcher to right or left to give a stepped effect to the joints. It is sometimes called Dutch bond;English garden-wall bond (f ): also American bond, common bond, or Liverpool bond, it has one course of headers to every three to (usually) five stretcher-courses, with a queen-closer introduced next to the quoin-header in the header course. Other variations occur;facing bond: thin fine bricks employed to face a thicker wall of common bricks. In many C18 and C19 brick walls, outer skins of normal-sized facing bricks often did not bond with the common-brick backing except when an occasional tie was included: the headers of such walls in Flemish bond would then be snapped or snap-headers;Flemish bond (g): alternate headers and stretchers in each course with closers next to the header quoins—variants may have three or five stretchers to each header. Double Flemish bond shows the bond on both faces of the wall;Flemish cross-bond: as Flemish bond, but with additional headers at intervals instead of stretchers;Flemish garden-wall bond (h): also Scotch or Sussex bond, it has courses of three or five stretchers between each pair of headers, continued along each course and contrived so that the header lies over the central one of the group of stretchers in the course above and below;Flemish stretcher-bond (i): also called American with Flemish bond, it has courses of alternate headers and stretchers, sandwiching several courses of stretchers. Sometimes there can be anything from one to six courses of stretchers instead of the commoner three courses;flying bond: see Monk bond;header bond (j): also bastard or heading bond, it hasonly headers on the wall-surfaces, is verystrong, and is useful for engineering work orfor curved walls. However, where the headerbond is the outer leaf of a cavity-wall, the bricksmight be snapped or snap-header;heading bond: see header bond;herringbone bond: bricks laid in diagonal zig-zag fashion, with each course laid at right angles to the one below;honeycomb bond: brickwork with the omission (usually) of headers in a pattern to permit ventilation, or for decoration;hoop-iron bond: reinforced brickwork in which flat iron bars dipped in tar and sanded are laid in every sixth course;irregular bond (l): bond using headers, but with no particular or consistent pattern, with broken vertical joints;lacing bond (m): one or more courses of bricks or tiles establishing a regular reinforcement and bond in a wall of flint, cobbles, etc.;Liverpool bond: see English garden-wall bond above;Loudon's hollow wall (n): essentially a hollow wall in Flemish bond with a cavity between the stretchers and a brick slip or closure behind each header to make up the full thickness of the wall. Invented by J. C. Loudon, it was both strong and aesthetically acceptable, and allowed heat to pass through the cavity, so was ideal where certain plants were to be trainedagainst it, as in a garden-wall, kitchen-garden, greenhouse, or conservatory;mixed garden bond (o): also called mixed garden-wall bond, it is essentially a variant on Flemish bond, but with two to five courses of stretchers, then a course of stretcher-header-stretcher, then three to five more of stretchers. Headers are not placed directly above each other in any regular pattern;Monk bond (p): also called flying bond or Yorks. bond, it is a variant on Flemish bond, with each course consisting of two stretchers rather than one between each pair of headers, each header placed over the joint between pairs of stretchers. Closers are required;quarter bond: also quarter bonding or raking stretcher bond, it is a variant on stretcher bond with each brick overlapping the brick below by a quarter-brick;quetta bond: variant on Flemish bond with continuous vertical gaps left inside the wall thickness filled with reinforcement and mortar;raking bonds: courses laid alternately in different directions, such as herringbone;raking stretcher bond (q): also quarter bonding or quarter bond, a variant on stretcher bond with each brick overlapping the brick below by a quarter brick;rat-trap bond (r): also Chinese, rowlock, or Silverlock's bond, it is a variant on Flemish or Sussex bond with courses of alternate headers and stretchers in each course laid on edge rather than on bed, the stretchers forming outer and inner leaves of bricks laid on edge with a cavity between them, and the headers (laid on the centre of each stretcher-on-edge) acting as bonders. Although very economical, it is not watertight, so if used for dwellings has to be rendered on the outside. The main virtue was that its hollow centre could be heated and used for walls against which plants could be grown. In the vicinity of Ware, Hertfordshire, what appears to be rat-trap bond may be a wall of Hitch hollow bricks of complex interlocking forms invented by Caleb Hitch in 1828;Scotch bond: see Flemish garden-wall bond;Silverlock's bond: see rat-trap bond above;single Flemish bond (s): with the appearance of Flemish bond on the outside face of a wall more than one brick-length thick. Double Flemish bond (t) is contrived to look like Flemish bond on both the inner and outer faces;stack bond (u): bricks laid on end with continuous vertical joints and no bond, so unsuitable for structural load-bearing walls;staggered Flemish bond: see Dutch bond;stretcher-bond (v): stretchers only, each lap being half a stretcher, commonly found in cavity walls;Sussex bond: also called Sussex garden-wall bond, it is the same as Flemish garden-wall bond; and Yorkshire bond: as Monk bond.Types and colours of pointing (the application of a superior mortar-finish to the raked-out joints (mortar between adjacent bricks, horizontally and vertically)) of ordinary mortar in brickwork are very important for appearance, stability, and weathering. Some common joints are:bag-rubbed pointing: flush pointing slightly recessed in the middle, so a type of rubbed joint;bastard tuck-pointing: imitation tuck-pointing of mortar only, with a profile similar to that of real tuck-pointing;bucket-handled joint: see keyed joint;flush joint: mortar flush with the brick faces;hungry joint: deeply recessed pointing to enable the outline of every brick or stone to be emphasized;keyed joint: called a bucket-handled joint, the mortar is indented with a segmental profile. Also a joint raked out to give a key to plaster or stucco;overhand struck joint: straight joint struck diagonally downwards, starting flush with the upper course;raked-out joint: joint cleared of mortar to a depth of 10–15 mm from the face of the brickwork for decorative purposes, to provide a key for plaster, or to permit a different type of pointing;recessed joint: set back from the face;ribbon-pointing: mortar standing proud of the stones. It is both unsightly and traps water, which damages the wall when it freezes, and became a common problem in the second half of C20 when untrained masons were allowed to get away with it;rubbed joint: flush joint made by rubbing excess mortar off the surface with a rag, rubber, etc.;ruled joint: also scored joint, in which grooves are ruled by running the point of a trowel against a straight-edge to give the appearance of very precise work;struck joint: straight joint struck diagonally, the bottom set back, and the top flush with the course below;tuck-pointing: mortar the same colour as the brickwork is set flush in the joints, and a groove formed along the centre of each joint into which is tucked a precise band of lime-putty to which a small amount of silver sand is added: this putty projects a few millimetres, and the top and bottom edges are trimmed in straight lines. In first-class work the vertical tucks are slightly narrower than the horizontal;vee-jointing: a V-shaped channel formed in a flush joint;weathered joint: straight joint struck diagonally, the top set back, and the bottom flush with the course below.

Bibliography

Brunskill (1990);
J. Campbell & and Pryce (2004);
N. Lloyd (1925);
Lynch (1990, 1994–6);
W. McKay (1957);
Joseph Kilner

Brick

Background

The term brick refers to small units of building material, often made from fired clay and secured with mortar, a bonding agent comprising of cement, sand, and water. Long a popular material, brick retains heat, with-stands corrosion, and resists fire. Because each unit is small—usually four inches wide and twice as long, brick is an ideal material for structures in confined spaces, as well as for curved designs. Moreover, with minimal upkeep, brick buildings generally last a long time.

For the above-cited practical reasons and because it is also an aesthetically pleasing medium, brick has been used as a building material for at least 5,000 years. The first brick was probably made in the Middle East, between the Tigris and Euphrates rivers in what is now Iraq. Lacking the stone their contemporaries in other regions used for permanent structures, early builders here relied on the abundant natural materials to make their sun-baked bricks. These, however, were of limited use because they lacked durability and could not be used outdoors; exposure to the elements caused them to disintegrate. The Babylonians, who later dominated Mesopotamia, were the first to fire bricks, from which many of their tower-temples were constructed.

From the Middle East the art of brickmaking spread west to what is now Egypt and east to Persia and India. Although the Greeks, having a plentiful supply of stone, did not use much brick, evidence of brick kilns and structures remains throughout the Roman Empire. However, with the decline and fall of Rome, brickmaking in Europe soon diminished. It did not resume until the 1200s, when the Dutch made bricks that they seem to have exported to England. In the Americas, people began to use brick during the sixteenth century. It was the Dutch, however, who were considered expert craftsmen.

Prior to the mid-1800s, people made bricks in small batches, relying on relatively inefficient firing methods. One of the most widely used was an open clamp, in which bricks were placed on a fire beneath a layer of dirt and used bricks. As the fire died down over the course of several weeks, the bricks fired. Such methods gradually became obsolete after 1865, when the Hoffmann kiln was invented in Germany. Better suited to the manufacture of large numbers of bricks, this kiln contained a series of compartments through which stacked bricks were transferred for pre-heating, burning, and cooling.

Brickmaking improvements have continued into the twentieth century. Improvements include rendering brick shape absolutely uniform, lessening weight, and speeding up the firing process. For example, modern bricks are seldom solid. Some are pressed into shape, which leaves a frog, or depression, on their top surface. Others are extruded with holes that will later expedite the firing process by exposing a larger amount of surface area to heat. Both techniques lessen weight without reducing strength.

However, while the production process has definitely improved, the market for brick has not. Brick does have the largest share of the opaque materials market for commercial building, and it continues to be used as a siding material in the housing industry. However, other siding materials such as wood, stucco, aluminum, plaster, and vinyl are strong competitors because they cost up to 50 percent less, and some (notably stucco and plaster) offer built-in insulation. Yet these systems can cost up to 1.75 times that of brick, which also requires less maintenance. Other materials that compete with brick despite their usually higher cost include precast concrete panels, glass, stone, artificial stone, concrete masonry, and combinations of these materials, because advances in manufacturing and design have made such materials more attractive to the builder. According to the U.S. Industrial Outlook, the use of brick as a siding material for single-family homes dropped from 26 percent in 1984 to 17 percent in 1989.

Raw Materials

Natural clay minerals, including kaolin and shale, make up the main body of brick. Small amounts of manganese, barium, and other additives are blended with the clay to produce different shades, and barium carbonate is used to improve brick's chemical resistance to the elements. Many other additives have been used in brick, including byproducts from papermaking, ammonium compounds, wetting agents, flocculents (which cause particles to form loose clusters) and deflocculents (which disperse such clusters). Some clays require the addition of sand or grog (pre-ground, pre-fired material such as scrap brick).

A wide variety of coating materials and methods are used to produce brick of a certain color or surface texture. To create a typical coating, sand (the main component) is mechanically mixed with some type of colorant. Sometimes a flux or frit (a glass containing colorants) is added to produce surface textures. The flux lowers the melting temperature of the sand so it can bond to the brick surface. Other materials including graded fired and unfired brick, nepheline syenite, and graded aggregate can be used as well.

The Manufacturing
Process

The initial step in producing brick is crushing and grinding the raw materials in a separator and a jaw crusher. Next, the blend of ingredients desired for each particular batch is selected and filtered before being sent on to one of three brick shaping processes—extrusion, molding, or pressing, the first of which is the most adaptable and thus the most common. Once the bricks are formed and any subsequent procedures performed, they are dried to remove excess moisture that might otherwise cause cracking during the ensuing firing process. Next, they are fired in ovens and then cooled. Finally, they are dehacked—automatically stacked, wrapped with steel bands, and padded with plastic corner protectors.

Grinding, sizing, and combining
raw materials

• 1 First, each of the ingredients is conveyed to a separator that removes oversize material. A jaw crusher with horizontal steel plates then squeezes the particles, rendering them still smaller. After the raw materials for each batch of bricks have been selected, a scalping screen is often used to separate the different sizes of material. Material of the correct size is sent to storage silos, and over-sized material goes to a hammermill, which pulverizes it with rapidly moving steel hammers. The hammermill uses another screen to control the maximum size of particle leaving the mill, and discharge goes to a number of vibrating screens that separate out material of improper size before it is sent on to the next phase of production.

Extrusion

• 2 With extrusion, the most common method of brick forming, pulverized material and water are fed into one end of a pug mill, which uses knives on a rotating shaft to cut through and fold together material in a shallow chamber. The blend is then fed into an extruder at the far end of the mill. The extruder usually consists of two chambers. The first removes air from the ground clay with a vacuum, thereby preventing cracking and other defects. The second chamber, a high-pressure cylinder, compacts the material so the auger can extrude it through the die. After it is compressed, the plastic material is forced out of the chamber though a specially shaped die orifice. The cross-section of the extruded column, called the "pug," is formed into the shape of the die. Sections of desired length are cut to size with rotating knives or stiff wires.

  In molding, soft, wet clay is shaped in a mold, usually a wooden box. The interior of the box is often coated with sand, which provides the desired texture and facilitates removing the formed brick from the mold. Water can also be used to assist release. Pressing, the third type of brick forming, requires a material with low water content. The material is placed in a die and then compacted with a steel plunger set at a desired pressure. More regular in shape and sharper in outline than brick made with the other two methods, pressed bricks also feature frogs.

Chamfering the brick

• 3 Chamfering machines were developed to produce a furrow in brick for such applications as paving. These machines use rollers to indent the brick as it is being extruded. They are sometimes equipped with wire cutters to do the chamfering and cutting in one step. Such machines can produce as many as 20,000 units per hour.

Coating

• 4 The choice of sand coating, also applied as the brick is extruded, depends on how soft or hard the extruded material is. A continuous, vibrating feeder is used to coat soft material, whereas for textured material the coating may have to be brushed or rolled on. For harder materials a pressure roller or compressed air is used, and, for extremely hard materials, sand blasting is required.

Drying

• 5 Before the brick is fired, it must be dried to remove excess moisture. If this moisture is not removed, the water will burn off too quickly during firing, causing cracking. Two types of dryers are used. Tunnel dryers use cars to move the brick through humidity-controlled zones that prevent cracking. They consist of a long chamber through which the ware is slowly pushed. External sources of fan-circulated hot air are forced into the dryer to speed the process.
• 6 Automatic chamber dryers are also used, especially in Europe. The extruded bricks are automatically placed in rows on two parallel bars. The bricks are then fed onto special racks with finger-like devices that hold several pairs of bars in multiple layers. These racks are then transferred by rail-mounted transfer cars or by lift trucks into the dryers.

Firing

• 7 After drying, the brick is loaded onto cars (usually automatically) and fired to high temperatures in furnaces called kilns. In general, the cars that moved the bricks through the drying process are also used to convey them through the tunnel kiln. These cars are pushed through the kiln's continuously maintained temperature zones at a specific rate that depends on the material. The majority of kilns in the United States use gas as a fuel source, though a third of the brick currently produced is fired using solid fuels such as sawdust and coal. Tunnel kilns have changed in design from high-load, narrow-width kilns to shorter, lower-set wider kilns that can fire more brick. This type of design has also led to high-velocity, long-flame, and low-temperature flame burners, which have improved temperature uniformity and lowered fuel consumption.

Setting and packaging

• 8 After the brick is fired and cooled, it is unloaded from the kiln car via the dehacking process, which has been automated to the point where almost all manual brickhandling is eliminated. Automated setting machines have been developed that can set brick at rates of over 18,000 per hour and can rotate the brick 180 degrees. Usually set in rows eleven bricks wide, a stack is wrapped with steel bands and fitted with plastic strips that serve as corner protectors. The packaged brick is then shipped to the job site, where it is typically unloaded using boom trucks.

Quality Control

Though the brick industry is often considered unsophisticated, many manufacturers are participating in total quality management and statistical control programs. The latter involves establishing control limits for a certain process (such as temperature during drying or firing) and tracking the parameter to make sure the relevant processes are kept within the limits. Therefore, the process can be controlled as it happens, preventing defects and improving yields.

A variety of physical and mechanical properties must be measured and must comply with standards set by the American Society of Testing and Materials (ASTM). These properties include physical dimensions, density, and mechanical strength. Another important property is freeze-thaw durability, where the brick is tested under conditions that are supposed to simulate what is encountered in the outdoors. However, current tests are inadequate and do not really correlate to actual conditions. What passes in the laboratory may not pass in the field. Therefore, the brick industry is trying to develop a more accurate test.

A similar problem exists with a condition known as efflorescence, which occurs when water dissolves certain elements (salt is among the most common) in exterior sources, mortar, or the brick itself. The residual deposits of soluble material produce surface discoloration that can be worsened by improper cleaning. When salt deposits become insoluble, the efflorescence worsens, requiring extensive cleaning. Though a brick may pass the laboratory test, it could fail in the field due to improper design or building practices. Therefore, brick companies are developing their own in-house testing procedures, and research is continuing to develop a more reliable standard test.

The Future

Currently, the use of brick has remained steady, at around seven to nine billion a year, down from the 15 billion used annually during the early 1900s. In an effort to increase demand, the brick industry continues to explore alternative markets and to improve quality and productivity. Fuel efficiency has also improved, and by the year 2025 brick manufacturers may even be firing their brick with solar energy. However, such changes in technology will occur only if there is still a demand for brick.

Even if this demand continues, the brick industry both here and abroad faces another challenge: it will soon be forced to comply with environmental regulations, especially in the area of fluorine emissions. Fluorine, a byproduct of the brickmaking process, is a highly reactive element that is dangerous to humans. Long-term exposure can cause kidney and liver damage, digestive problems, and changes in teeth and bones, and the Environmental Protection Agency (EPA) has consequently established maximum exposure limits. To lessen the dangers posed by fluorine emissions, brickworks can install scrubbers, but they are expensive. While some plants have already installed such systems, the U.S. brick industry is trying to play a more important role in developing less expensive emissions testing methods and establishing emission limits. If the brick industry cannot persuade federal regulators to lower their requirements, it is quite possible that the industry could shrink in size, as some companies cannot afford to comply and will go out of business.

Where To Learn More

Books

Bender, Willi and Frank Handle. Brick and Tile Making. Bauverlag GmbH, 1985.

Jones, J. T. and M. F. Berard. Ceramics: Industrial Processing and Testing. Iowa State University Press, 1972.

Robinson, Gilbert C. Ceramics and Glasses. ASM International, 1992, pp. 943-950.

Periodicals

"Trends in Brick Plant Operations," The American Ceramic Society Bulletin. 1992, pp. 69-74.

Hall, Alvin. "Using Computer-Aided Manufacturing to Build Better Brick," The American Ceramic Society Bulletin. 1990, pp. 80-82.

Richards, Robert W. "Brick Manufacturing from Past to Present," The American Ceramic Society Bulletin. May, 1990, pp. 807-813.

Sheppard, Laurel M. "Making Brick and Meeting Regulations," The American Ceramic Society Bulletin. 1993.

"Lodge Lane Brickworks: A Breakthrough in the Reduction Firing of Bricks," Ziegelindustrie. September, 1992, pp. 344-341.

—L S. Millberg

Brick

History

Brick manufacturing

Types of brick

Resources

A brick is a block of clay or other similar material, usually in the shape of a rectangle, that is baked so that it becomes hard enough to be used for building houses and other structures. Bricks are one of the oldest types of building blocks. They are an ideal building material because they are relatively cheap to make, very durable, and require little maintenance. Bricks are usually made of kiln-baked mixtures of clay. People who work with brick are called brick masons or bricklayers. Among the numerous jobs they perform are the laying of walkways, building of external walls on office buildings, and building and repairing of fireplaces, chimneys walls, floors, and other structures.

In ancient times, bricks were made of mud and dried in the sun. Modern bricks are made from concrete, sand and lime, and glass. The physical and chemical characteristics of the raw materials used to make bricks, along with the temperature at which they are baked, determine the color and hardness of the finished product. Bricks are made in standard sizes, are usually twice as long as they are wide, and, since most bricklaying is done manually, they are made small enough to fit in the hand. Bricklayers use a trowel to cover each brick with mortar—a mixture of cement, sand, and water. The mortar hardens when dry and keeps the bricks in place. Bricks are arranged in various patterns, called bonds, for strength.

History

Archaeologists have found bricks in the Middle East dating 10,000 years ago. Scientists suggest that these bricks were made from mud left after the rivers in that area flooded. The bricks were molded by hand, and left in the sun to dry. Structures were built by layering the bricks using mud and tar as mortar. The ancient city of Ur (in what is now Iraq) was built with mud bricks around 4000 BC. The Bible (Exodus 1:14; 5:4-19) provides the earliest written documentation of brick production—the Israelites made bricks for their Egyptian rulers. These bricks were made of clay dug from the earth, mixed with straw, and baked in crude ovens or burned in a fire. Many ancient structures made of bricks, such as the Great Wall of China and remnants of Roman buildings, are still standing today. The Romans further developed kiln-baked bricks and spread the art of brick making throughout Europe.

The oldest type of brick in the Western Hemisphere is the adobe brick. Adobe bricks are made from adobe soil, comprised of clay, quartz, and other minerals, and baked in the sun. Adobe soil can be found in dry regions throughout the world, but most notably in Central America, Mexico, and the southwestern United States. The Pyramid of the Sun was built of adobe bricks by the Aztecs in the fifteenth century and is still standing. In North America, bricks were used as early as the seventeenth century. Bricks were used extensively for building new factories and homes during the Industrial Revolution. Until the nineteenth century, raw materials for bricks were mined and mixed, and bricks were formed, by manual labor. The first brick making machines were steam powered, and the bricks were fired with wood or coal as fuel. Modern brick making equipment is powered by gas and electricity. Some manufacturers still produce bricks by hand, but the majority are machine made.

Brick manufacturing

The manufacture of bricks entails several steps and starts with obtaining the raw materials. Clays are mined from open pits or underground mines. Storage areas are located at the mining site so that portions from various locations, digs, can be blended. The clay mixture goes through a process called primary crushing, where the clay is put through giant rollers that break the clay into small chunks. This mixture is transported to the manufacturing site, where the clay mixture is pulverized and screened to remove impurities. Further blending of materials may take place at this time.

There are three methods of forming bricks. The most common is the stiff-mud process where the clay blend is put into a machine called a pug mill that mixes the clay with water (12 to 15% by weight), kneads the mixture, removes trapped air, and transfers the mixture to an auger machine. The auger forces or extrudes the wet clay through a die that forms a continuous rectangle-shaped column. The column is cut with steel wires into desired lengths. The newly formed bricks are place on drying racks for a few days and then fired in a kiln. The softmud process is used when the mined clay is naturally too wet (20 to 30% by weight) to undergo the stiff-mud process. The clay is mixed, extruded, and placed in lubricated molds. Each mold makes six to eight bricks. The drying process takes more time than with stiff mud, but the firing procedure is the same. The third method is the dry-press process, which is most commonly used when making refractory bricks. The clay has minimal water content (up to 10% by weight) and is exposed to high pressure (in a hydraulic or mechanical press) while in the molds. The bricks are dried and fired. While still damp and moldable, textures, designs, or functional grooves can be pressed into the brick. Special glazes can be applied for decorative and for functional purposes.

Firing or burning the bricks takes two to five days. The most common type of kiln used to fire bricks is the tunnel kiln, where the bricks, stacked on cars, move slowly though a long chamber or tunnel. Many changes in the physical properties occur during the firing process. During firing, any residual water evaporates, some minerals melt, blend, and fuse, and organic matter oxidizes. The hardness of the brick increases and the color develops. The whole process of making bricks takes 10 to 12 days.

With handmade bricks, the clay is kneaded and put into molds. Excess clay is skimmed off the top of the mold, and the brick is then dumped out, dried, and fired. Handmade bricks are usually more expensive than machine-made bricks. They are often used in special projects, such as historical restoration.

Types of brick

Some bricks are made for specific purposes and are made of certain raw materials, formed in a particular shape, or with added special textures or glazes. Common brick is the everyday building brick. They are not made of special materials, and do not have special marks, color, or texture. Common brick is typically red and sometimes used as a “backup” brick, depending on the quality. Face brick is often applied on top of common backup brick. Face brick can be obtained in a variety of colors, has a uniform surface appearance and color, is more durable, and is graded according to its ability to withstand freezing temperatures and moisture. Refractory bricks are made from fireclays—clays with a high alumina or silica content or non-clay minerals such as bauxite, zircon, silicon carbide, or dolomite. Fireclays are heat resistant and are used in various types of furnaces, kilns, and fireplaces. Calcium silicate bricks are often made in areas where clay is not readily available. Glazed bricks are made primarily for walls in buildings such as dairies, hospitals, and laboratories, where easy cleaning is necessary.

See also Stone and masonry.

Resources

BOOKS

Campbell, James W.P. Brick: A World History. London, UK: Thames & Hudson, 2003.

Cowan, Henry J. The Master Builders. New York: Wiley, 1977.

Olin, Harold B. Construction; Principles, Materials and Methods. Danville, IL: Interstate Printers and Publishers, 1980.

Plumridge, Andrew. Brickwork: Architecture and Design. London, UK: Seven Dials, 2000.

Christine Miner Minderovic

Brick

Bricks are one of the oldest types of building blocks. They are an ideal building material because they are relatively cheap to make, very durable, and require little maintenance. Bricks are usually made of kiln-baked mixtures of clay. In ancient times, bricks were made of mud and dried in the sun ; modern bricks are made from concrete , sand and lime, and glass . The physical and chemical characteristics of the raw materials used to make bricks, along with the temperature at which they are baked, determine the color and hardness of the finished product. Bricks are made in standard sizes, are usually twice as long as they are wide and, since most bricklaying is done manually, are made small enough to fit in the hand. Bricklayers use a trowel to cover each brick with mortar—a mixture of cement, sand, and water . The mortar hardens when dry and keeps the bricks in place. Bricks are arranged in various patterns, called bonds, for strength.

History

Archaeologists have found bricks in the Middle East dating 10,000 years ago. Scientists suggest that these bricks were made from mud left after the rivers in that area flooded. The bricks were molded by hand and left in the sun to dry. Structures were built by layering the bricks using mud and tar as mortar. The ancient city of Ur (modern Iraq) was built with mud bricks around 4,000 b.c. The Bible (Exodus 1:14; 5:4-19) provides the earliest written documentation of brick production—the Israelites made bricks for their Egyptian rulers. These bricks were made of clay dug from the earth , mixed with straw, and baked in crude ovens or burned in a fire. Many ancient structures made of bricks, such as the Great Wall of China and remnants of Roman buildings, are still standing today. The Romans further developed kiln-baked bricks and spread the art of brickmaking throughout Europe .

The oldest type of brick in the Western Hemisphere is the adobe brick. Adobe bricks are made from adobe soil , comprised of clay, quartz, and other minerals , and baked in the sun. Adobe soil can be found in dry regions throughout the world, but most notably in Central America, Mexico, and the southwestern United States. The Pyramid of the Sun was built of adobe bricks by the Aztecs in the fifteenth century and is still standing. In North America , bricks were used as early as the seventeenth century. Bricks were used extensively for building new factories and homes during the Industrial Revolution . Until the nineteenth century, raw materials for bricks were mined and mixed, and bricks were formed, by manual labor. The first brickmaking machines were steam powered, and the bricks were fired with wood or coal as fuel. Modern brickmaking equipment is powered bygas and electricity . Some manufacturers still produce bricks by hand, but the majority are machine made.

Brick manufacturing

The manufacture of bricks entails several steps and starts with obtaining the raw materials. Clays are mined from open pits or underground mines. Storage areas are located at the mining site so that portions from various "digs" can be blended. The clay mixture goes through a process called primary crushing, where the clay is put through giant rollers that break the clay into small chunks. This mixture is transported to the manufacturing site, where the clay mixture is pulverized and screened to remove impurities. Further blending of materials may take place at this time.

There are three methods of forming bricks. The most common is the stiff-mud process where the clay blend is put into a machine called a pug mill that mixes the clay with water (12-15% by weight), kneads the mixture, removes trapped air, and transfers the mixture to an auger machine. The auger forces or extrudes the wet clay through a die that forms a continuous rectangle-shaped column. The column is cut with steel wires into desired lengths. The newly formed bricks are place on drying racks for a few days and then fired in a kiln. The soft-mud process is used when the mined clay is naturally too wet (20-30% by weight) to undergo the stiff-mud process. The clay is mixed, extruded, and placed in lubricated molds. Each mold makes six to eight bricks. The drying process takes more time than with stiff mud, but the firing procedure is the same. The third method is the dry-press process, which is most commonly used when making refractory bricks. The clay has minimal water content (up to 10% by weight) and is exposed to high pressure (in a hydraulic or mechanical press) while in the molds. The bricks are dried and fired. While still damp and moldable, textures, designs, or functional grooves can be pressed into the brick. Special glazes can be applied for decorative and for functional purposes.

Firing or burning the bricks takes two to five days. The most common type of kiln used to fire bricks is the tunnel kiln, where the bricks, stacked on cars, move slowly though a long chamber or tunnel. Many changes in the physical properties occur during the firing process. During firing, any residual water evaporates, some minerals melt, blend, and fuse, and organic matter oxidizes. The hardness of the brick increases and the color develops. The whole process of making bricks takes 10-12 days.

With handmade bricks, the clay is kneaded and put into molds. Excess clay is skimmed off the top of the mold, and the brick is then dumped out, dried, and fired. Handmade bricks are usually more expensive than machine-made bricks. They are often used in special projects, such as historical restoration.

Types of brick

Some bricks are made for specific purposes and are made of certain raw materials, formed in a particular shape, or with added special textures or glazes. Common brick is the everyday building brick. They are not made of special materials, and do not have special marks, color, or texture. Common brick is typically red and sometimes used as a "backup" brick, depending on the quality. Face brick is often applied on top of common backup brick. Face brick can be obtained in a variety of colors, has a uniform surface appearance and color, is more durable, and is graded according to its ability to withstand freezing temperatures and moisture. Refractory bricks are made from fireclays—clays with a high alumina or silica content or nonclay minerals such as bauxite, zircon, silicon carbide, or dolomite. Fireclays are heat resistant and are used in various types of furnaces, kilns, and fireplaces. Calcium silicate bricks are often made in areas where clay is not readily available. Glazed bricks are made primarily for walls in buildings such as dairies, hospitals, and laboratories, where easy cleaning is necessary.

See also Stone and masonry.

Resources

books

Cowan, Henry J. The Master Builders. New York: Wiley, 1977.

Olin, Harold B. Construction; Principles, Materials and Methods. Danville, IL: Interstate Printers and Publishers, 1980.

Christine Miner Minderovic

brick • n. a small rectangular block typically made of fired or sun-dried clay, used in building. ∎  bricks collectively as a building material: this mill was built of brick. ∎  a small, rectangular object: a brick of ice cream. • v. [tr.] (often be bricked) block or enclose with a wall of bricks: the doors have been bricked up.PHRASES: hit (or run into) a brick wall face an insuperable problem or obstacle while trying to do something.like a ton of bricks inf. with crushing weight, force, or authority: all her years of marriage suddenly fell on her like a ton of bricks.