CLAY WORKING INDUSTRIES. 227 



The manufacture of fire brick on soft mud machinery can not be 

 specialty objected to as far as the structure of the product is concerned, 

 but in shape and finish it is not nearly the equal of hand made brick. 

 The moulds all have to be stroked or cut off level with a large metal 

 plate; this leaves one side of the brick rough and unpresentable. Also 

 to operate the brick machine to an advantage it is necessary to run it 

 something near its capacity, which is 25,000 to 30,000 per day. The dry- 

 ing of such a large quantity by hot floor is not usually possible, and the 

 use of racks and pallets become necessary as the brick are much too soft 

 when first made to stand handling of any kind. This fact makes their 

 repressing a source of considerable expense, as they have to be brought 

 out of the racks and pressed and then put back again or placed on a hot 

 floor or other drying apparatus. 



Hence, the limitations of the soft mud process; it makes a good 

 brick, strong and of good structure, but of bad appearance, and to 

 remedy its appearance by repressing is out of the question at the common 

 prices. On very high grade material it might be possible. In this con- 

 nection, the use of the iron clad dryer on the product of the soft mud 

 machine is interesting to note. The drying was effected without trouble 

 or cracking, and was carried on in connection with stiff mud bricks at the 

 same time. 



The use of auger or plunger brick machinery in the manufacture of 

 high grade brick is a constant temptation to the brick makers by reason 

 of the lessened cost of production. 



Aside from the structural defects of the bar from which the brick 

 are cut, the brick are too dense and compact for the best results, 

 and it is impossible to get the proper bond with the small quantity 

 of plastic clay which is used, unless the temper of the mixture be made 

 softer than the Auger machine will work to an advantage. The methods 

 of burning refractory bricks are beginning to experience some change ; 

 for many years past, almost the only process of burning was in the old up 

 draft clamp kilns, A great many works still retain them. But the 

 progressive members of the business have been introducing the down 

 draft kilns. The down draft kilns employed are mainly of the com- 

 mon round type. A few square Newcastle kilns, built in blocks or bat- 

 teries are in use. No Eudalys or other patent kilns are in use in the fire 

 brick business of this state. The Thomas kiln, a down draft kiln, of great 

 excellence, which originated from an effort to convert the old up draft 

 kilns into down draft is in use in the Scioto and Lawrence county d s- 

 tricts. The up draft kiln which furnished the main points of this 

 Thomas kiln was constructed as follows : 



The width of the kiln was twelve to thirteen feet inside ; the length, 

 though immaterial, was usually about thirty feet; the walls which were 

 about thirty inches thick, were pierced at intervals of every twenty-seven 

 inches by narrow fire holes, twelve or thirteen inches wide. These fire 



