CLAY WORKING INDUSTRIES. 235 



The hand moulding process, while using less machinery and power 

 than any other, produces a brick free from structural faults. Manufac- 

 ture by this process is largely a matter of labor, and the cost is now reg- 

 ulated by the price of union labor. Everything is reduced to a system, 

 and one standard price for an alloted quantity of brick per day is the rule 

 in all centers of production. The actual production of the various manu- 

 facturers thus costs about the same. Their only chance to economize, is 

 by management of the details, and the skill of burning; one burner may 

 produce a larger percentage of good brick than another. 



The soft mud machine makes a brick of good structural quality, but 

 every brick has one rough side where the mold is stroked off. The main 

 advantage of the machine over the hand moulding is the increased out- 

 put. The cost of the plant is much higher, however, a large part of the 

 expense being for racks and pallets for outside drying. 



The auger machine process for building brick is mainly confined to 

 the production of end cut brick. It is in this business that the automatic 

 end cutting machines originated. 



The formation of the bar of clay has nothing to do with the value of 

 the product for building purposes, and color or smoothness has about 

 as little, in the large markets. 



For building brick, the clays selected are usually plastic drift and 

 sedimentary clays. 



The preparation consists usually in passing through rollers to separ- 

 ate large stones, and to crush smaller ones, and a pug mill to temper the 

 clay. For the soft mud and hand moulding process no machinery except 

 a crude pug mill for preparation is used. The drying is accomplished by 

 the most elaborate dryers in the large factories, and by racks and open 

 yards in the smaller yards. Burning is altogether accomplished by the 

 use of clamp up-draft kilns. The use of oil fuel, and natural gas, has 

 been a temporary advantage to some few brickmakers, but has been of no 

 permanant profit to the industry. The firing of the kilns is done in the 

 arches, in the fire-holes or in outside furnaces. 



Stock brick are a grade between pressed front brick and the best 

 grades of common brick. The grade is dying out as the introduction 

 and perfection of the dry press process goes on. At one time stock brick 

 were the best that could be obtained. The method of manufacture is 

 much the same as that of common brick, except that they are subjected 

 to a pressing process after they have been allowed to partly dry, and be- 

 come of a stiff, cheesy consistency. At this temper the clay takes a beau- 

 tiful sharp edge, and if handled carefully the results are very fine. The 

 clays are selected to make a fine colored brick; no other will sell at the 

 advanced figures charged, and the burning is done generally in clamp 

 kilns, in which the arches, benches, sides, ends and top are made of com- 

 mon brick, and the stock brick are put in a compact mass in the center, 

 where they are all sure to be burnt hard and informally. The grading 



