The Evansville Pressed Brick Co., of Evansville, Ind., use a mixture of clays for producing vitrified street paving brick. Fire-clay, obtained from Lincoln, is mixed with clay obtained from their own yards. The clay is first thrown into a dry pan, where it is crushed by two large rollers, weighing three tons each. It is ground down into a powder. It is then carried by means of a belt, with buckets attached, to the pug-mill, where it is moistened and thoroughly ground and mixed. From the pug-mill it passes into the top of the stiff-clay machine. Here the process of mixing is concluded and the clay is ready for the moulds. By suitable mechanism it is moulded under a pressure of 50,000 pounds to the brick. This makes it an im possibility for defects to occur within the finished product. The moulded brick then passes out on a belt ; it is cut and placed on a car. When 500 are obtained the car is pushed down a track to the dry-house. In this the car remains for a period of about thirty-six hours. Steam is used in the dry house and temperature gradually increases. After leaving the dry-house, the product stands until it is ready to be placed in the kilns for burning.
The burning is done in down-draft kilns, the fires being held at finishing about twenty-four hours longer than for building brick.
The Purington Paving Brick Co., of Galesburg, Ill., use a shale clay, which during the last few years has become famous as the material from which the celebrated Galesburg paving brick are made. The shale is reduced to powder by being subjected to the action of two large size dry-pans, and after being rendered plastic by mixing with water, is formed into brick shape by two stiff-clay brick machines. From the ma chines the brick pass on cars into a steam dryer. Sixteen Eudaly down-draft kilns are used in which to thoroughly burn and vitrify the brick. These kilns are eighty-three by eighteen feet inside measurement. Crude oil is used for fuel in these works, and it has been demonstrated to be far superior to wood or coal, and the quality of product seems to be better and the vitrification more thorough and conWlete.
From one-fourth to one-third more time is consumed in burning than with the ordinary building brick. In burning, the brick shrinks from nine inches in length to eight inches, and proportionately in other directions. It is thoroughly vit rified throughout, and weighs five pounds. This brick will resist the best steel drill, and a chip will scratch glass.
A peculiarity about this plant is that no tight and loose pul leys are employed, clutches being used altogether.
The buildings are all of brick, being heated by steam, and it is intended to run winter and summer continuously. A coil of pipe is extended under the dry-pans, so as to prevent clay from freezing.
The Ottumwa Paving Brick and Construction Co., of Ottumwa, Iowa, use a mixture of strong clay and shale. The cars when loaded are drawn up into the clay house and dumped. Here workmen shovel.the clay and shale into a dry-pan. After being pulverized as fine as powder the material is hoisted by means of an elevator to the pug-mill on the second floor, where water is added and the material tempered. The material next passes by gravity to the brick machine, immediately below, where the brick is rapidly shaped by a stiff-clay brick machine. As fast as the brick are made they are loaded on cars and run into the artificial dryer, where they remain twenty-four hours. They are then taken from the dryer and placed in the kiln to be burned, this occupying some ten days.
The capacity of the plant is 50,000 brick per day and more than that number is frequently made. The six down-draft kilns have each a capacity of 250,000 brick.
The buildings at present occupied by the plant are a clay house, 30x100, a machine room, 30x70, and an artificial dryer, 30x140 feet.