American Brick

AMERICAN BRICK Classes and Standards.—In American practice a brick is a structural unit of burned clayey material, in the form of a rec tangular block, with the standard dimensions of 2+in. by Sin. by Sin. Bricks of other sizes, of other materials, and other structure than solid except limited perforations, have qualifying names, as :—fire bricks ; paving bricks ; sand lime, chrome, magnesite and silica bricks; insulating bricks; hollow bricks; Roman bricks, 1lin. by 4in. by i 2in. ; Norman brick, 2 $in. by 4in. by 1 tin. ; Old Virginia bricks, Sin. by 4in. by gin., etc. The standard size of a fire brick is 2iin. by 41in. by gin. and there are standard sizes in key, arch, wedge, split and soap fire bricks.

The following standard sizes for paving bricks were adopted in 1927 by the National Paving Brick Association : 21in. by 4in. by 8 1in., plain wire cut bricks, laid the 2 tin. depth. Sin. by 4in. by 81in., plain wire cut bricks, laid the 3in. depth. 31in. by 4in. by 82in., plain wire cut bricks, laid the 321n. depth. by 4in. by 82in., repressed block, laid the 4in. depth.

Sin. by 321n. by 82in., Dunn wire cut lug block, laid the Sin. depth.

Bond in Bricks.

Bricks are bonded into durable products in the process of burning by the fusion and subsequent hardening of the alkaline minerals and mineral salts, denominated fluxes, pres ent in the clay. As fusion and solution of the refractory grains progress with advancing temperature the ware changes from soft, to light hard, to hard, and finally to a vitrified product. In the latter the fused matrix predominates. The porosities range from as high as 25% in the soft bricks to io% or less in the hard bricks and to 5% or less in the vitrified bricks.

Processes.—The processes used in America are the soft mud, the stiff mud, and the dry press. The stiff plastic process inter mediate between the stiff mud and the dry press, used in Eng land is not used in America except to a limited degree and in a modified way in the manufacture of some fire clay products.

The soft mud hand moulding operation has been discontinued in America except in the manufacture of fire bricks and in this product it is gradually being superseded by other processes.

Soft Mud Machines.

Soft mud machine moulded bricks were first made in America in 1833, and next from 1840 to 1844 in Philadelphia, Pa. Within a few years machine moulding became the general practice but it did not entirely displace the hand moulding for nearly 4o years.

The maximum output of these machines was about 30,00o bricks per day which was the labour limit in striking to remove surplus clay from the moulds and bumping the moulds to loosen the bricks for dumping. The modern moulding machine is automatic. The mould sanding and feeding, the striking and the bumping, are done mechanically, and the labour required is performed by one man who places the pallets on the dumping frame. In the ma jority of installations wire rope carriers take the loaded pallets to the drying racks. With hand labour practically eliminated the soft mud machines produce upwards of ioo,000 bricks per day.

In the most modern plants the dry bricks are taken from the pallets in units of ten or less as may happen, and set on cars in units of 500 to 1,000 bricks as they will be set in the kilns. A crane equipped with a lifting fork sets these larger units in the proper place in the kiln in a single operation.

Dry Press Machines.

The first dry press of which there is record was put into operation in 1847 and in 1848 many such presses were in use. In 1856 a hydraulic press was built in Cleve land, Ohio, and was subsequently developed and put into opera tion in St. Louis, Mo.

These presses, which made ten bricks with each revolution of the machine became the basis of a large production which still continues. In 1878 a toggle joint press of American design was put into operation in Chicago, Ill.

About 1880 a number of toggle joint presses were developed and became the basis for a large output of dry pressed bricks through out the country, though the peak of such production has long since been passed.

Stiff Mud Machines.

In 1853, James W. Penfield of Wil loughby, Ohio, designed and put into operation a horse driven, intermittent, horizontal plunger, stiff mud machine which became the basis of an extensive manufacture of plunger stiff mud ma chines and a large output of stiff mud bricks. In 1862, Cyrus Chambers of Philadelphia, Pa., built and put into operation a stiff mud auger machine so-called the "sausage machine" with an automatic cutter, driven by steam power. This was the beginning of the numerous output of stiff mud bricks which predominate the market. In 1928 were many factories which produced more than 100,000 bricks per day from a single machine, and in the Chicago district, where a crane with lifting fork to. set the bricks in the kilns in large units is used, the output from a single machine is about 300,00o bricks per day.

Grinding Machines.

The clay preparing machinery is adapted to the nature of the clay or shale utilized. Granulators, disintegrators and rolls are used for soft clays, and dry pans for hard clays and shales. In the United States the dry pan with a capacity from 75 tons to 150 tons per day, ,depending upon the hardness of the material and the fineness of the grinding, is being replaced by a machine designated as a grinder which, in the heavier types, has the capacity of four or five dry pans, or a ton of ground clay per minute. The grinder differs from the dry pan in that the screening feature of the latter is entirely or largely eliminated in the former, and the rollers have been increased in weight in the heavier machines to upwards of seven tons each.

sorting is not required, clays are gathered by various types of scrapers but the machine chiefly used is a steam or electric driven shovel, commonly known as a steam shovel. When the material will stand in a vertical bank, a shale planer is used. This is a powerful chain elevator of the bucket type, but instead of buckets, cutting chisels are attached to the chains. This equipment cuts the material from top to bottom in a shallow cut, the cuttings dropping through chutes into industrial railway cars. As the cutting proceeds the machine advances auto matically along the vertical bank. The dug material is hauled to the factory by small locomotives (dinkeys). In the factory the lump hard clay or shale is dumped into a reciprocating feeder which spills it into a jaw, gyratory, or single roll crusher, the latter being the most widely used. The crushed clay is then conveyed to the dry pan or grinder into which it is automatically fed by a reciprocating or disk feeder. The pulverized clay is elevated, screened, and conveyed to the brick machine—stiff mud for ex ample—and fed into the pugmill by a disk feeder. Excess clay from the grinders is dumped into a storage bin to be used as occasion requires. Much heavy labour is thus eliminated.

Dryers.

Open yard drying has largely disappeared and air drying in racks is disappearing. In their place several types of artificial dryers are used, the type depending upon the available heat supply. The most widely used dryer is the tunnel type, in which the bricks on cars in units of 500 to 700 are moved through tunnels on tracks. The combustion gas type, designated as a radiated heat dryer, has ducts for the smoke gases under the tunnel tracks ; the common form has furnaces at one end of the dryer, connecting with the combustion gas ducts. In some instal lations the combustion gases from burning kilns are collected by fans and forced through the ducts. The progressive tunnel dryer collects the hot air from the cooling kiln, from steam coils heated by exhaust or live steam, from auxiliary furnaces, etc., and thus the heated air is put directly into the drying tunnel and comes in contact with the ware. Most tunnel dryers are distinctively humid ity dryers since the ware is moving in one direction and the hot air, with its accumulated vapour and decreasing temperature, is moving in the opposite direction. In the newer forms of humid ity dryers the main features are better air circulation among the ware and better control of the humidity. For soft mud bricks the pipe rack dryer is widely used. This consists of racks of closely spaced steam pipes upon which pallets of bricks rest. Fire bricks, because of the need of repressing after partial drying, are largely dried on steam heated floors, known as hot floors, though tunnel dryers are used to an increasing extent where the newer processes of manufacture have been adopted.

Kilns.

Every type of kiln is used. The original common clamp kiln, known as the stove kiln is used in some of the largest corn mon brick operations. This type of kiln lends itself admirably to operations where the bricks are set by machines. Many factories use the up-draft kiln which is identically a clamp kiln except the walls of the kiln are heavy and permanent. The down-draft kiln is most widely used, despite its greater fuel consumption because of the excellence of the results due to the effective control that it provides over the kiln atmospheres. This insures the production of every possible colour effect by oxidizing and reducing conditions, and also special colours by the use of minerals or salts in the final stages of the firing, such as zinc to produce a green color, nga nese to produce black, common salt for glazing, etc. Among the economizer types of kilns are the tunnel kiln, the compartment continuous kiln and the car tunnel kiln. The tunnel kilns often exceed 24 sections in length and are operated with two or more sets of fires, or in other words are operated as two or more kilns. The largest kiln of this type in America in 1928 was in Bessemer Quar ries, Ohio, producing paving bricks. This has 208 sections and when in full operation 1 o sets of fires are carried at the same time. The kiln is built in two parallel batteries, connected at the ends, and, if straightened out into a single battery, it would be more than a half mile long.

The compartment continuous kiln is an advance over the tunnel type, in that the draft often is distinctively down draft instead of being horizontal draft or serpentine draft as in the tunnel kiln and other solid floor kilns. This is used in many localities but since the advent of the car tunnel kiln but few new compartment kilns are installed. The car tunnel kiln, built in lengths of 300f t. to 40oft. and producing from 40,000 to 70,00o standard bricks per kiln per day, was in 1928 rapidly coming into use for the produc tion of bricks and fire bricks.

Bloated Bricks.—Clays containing carbon and sulphur min erals, notably iron pyrite, if burned too rapidly in the early stages of the firing during oxidation, bloat when the temperatures are carried up to the finishing point. This condition is commonly termed black coring because the core of the ware is black from the unburned carbon and the reduction of the iron. The bloating is due to the entrapped gases which cannot escape as vitrification of the clay takes place. In many instances such bloated ware will float in water. During the World War bloated burned clays were produced for the building of concrete ships, and since are finding use in making light weight concrete and light weight building tile.

Texture Bricks.—From Colonial days to the advent of the dry pressed bricks, the bricks were rough, misshapen and irregular in size. The better grades were selected for line (face) bricks and the poorer grades for inwalls. With the appearance of the dry pressed brick, uniform in size and perfect in form, the distinction between common and face, or pressed, bricks became sharply drawn. The manufacturers of stiff mud bricks met the dry press standard by re-pressing the bricks in a press akin to a dry press. Then followed an era of construction with perfect bricks, uni form in colour and laid with thin mortar joints. The bricks corn prised the sole structural feature of the wall. In 1903 in New Lexington, 0., the wire-cut texture brick was first produced. Wires were stretched across the die to cut off a thin slice from the sur faces of the stiff mud bricks, leaving a rough serrated surface. The artistic value of this surface texture was quickly recognized by architects and the manufacture of wire-cut face bricks spread throughout the country. Numerous other textures have been pro duced by various scratching devices, to some of which distinctive names have been given, as tapestry, rug, oak bark, raglan, velvet, astrakhan, etc. With the advent of the texture brick the mortar joint, formerly merely a structural factor to be hidden, has come to be recognized as a characteristic feature in brick wall construc tion. Uniform shading has given way to mingled shades including every colour and shade possible in burned bricks. The American wall built of all stretchers with hidden bond, has given way to various bonds—English, Flemish, Dutch and a wide range of diaper work. The production of polychrome glazed colour effects, produced by spraying the stiff mud bricks with glazes, has begun to off-set the increasing use of terra cotta products.

Scum and Efflorescence.

A white coating on bricks from the kiln, known as scum or whitewash, and white, yellow to green coatings which come to the surfaces of brick walls, known as efflorescence, are serious brick making problems.

Rattler Tests.—Paving bricks are tested in a machine known as a rattler, adapted from a similar machine used in foundries for cleaning castings. It is approximately a cylinder, 28in. in diameter and 2oin. wide. The periphery is made of six inch channel bars bolted to the side frames and slightly spaced to permit the escape of the dust. These are lined with steel staves. The charge con sists of about i oo pounds of the bricks, 2251b. of one inch and 751b. of four inch cast iron balls. In the test the machine is rotated at the rate of 3o revolutions per minute for a period of one hour. The loss in the weight of the bricks by abrasion is termed rattler loss, and specifications for paving bricks commonly range between 18% and 24% rattler loss.

Output and Value.

The U.S. Department of Commerce re port for 1926 gives the following statistics regarding the industry: Number of Output in establishments thousands Value Common bricks . . 1,220 7,520,411 $88,249,925 Face bricks . . . 44,516,236 Vitrified bricks . . 131 467,58o 10,284,741 Hollow bricks 39 692,258 (This does not include hollow building tile having a value of Enameled bricks . • 9 $1,275,692 Fire bricks . 244 1,016,879 40,992,018 (This does not include 4o establishments making special refractory shapes.) The total value of all clay products in the United States in 1926 was See H. L. Whittemore, "Equalizer Apparatus for Transverse Tests of Bricks," U.S. Bur. Stand., Tech. Pap. No. 251 (1924) ; W. F. Kirk, "Productivity Costs in Common-Brick Industry, U.S. Bur. Labor Stat., Bull. No. 356 (1924) ; and A. I. Andrews "The Making of Dolomite Brick," Ohio State Univ. Engr. Serv., Bull. No. 31 (Columbus, 0., . (E. Lo.)