100 GEOLOGY OF OHIO. 



Such is the process of washing clays. The machinery has been 

 greatly perfected in late years and fine grade clays can hardly be sold now 

 until they have been washed and dried again to atmospheric condition. 



The use of steam in assisting to disintegrate the clay in the blunger 

 has been tried with very great success in a few places in Ohio. The warm 

 water does its work quicker, the liquid filters much faster, and the men 

 engaged in handling the wet clay in the winter time are relieved from the 

 suffering from cold. 



The peculiar quality of washed clay is its fineness and eveness of 

 structure. No two particles of the original lump are together in the 

 washed clay. To a certain extent, the waxy toughness of the original 

 clay is gone; the result is more granular, though finer grained clay, which 

 under the hands of the turner usually works " short." The clay is purer 

 by the removal of whatever may be of a soluble nature, like lime salts. 

 Iron existing in the form of grains is ver3' apt to be removed with the 

 coarse sand. Clay by this process is not considered so "safe" in the kiln 

 as ground clay, on account of its fine, close-grained body, and liability to 

 checking in cooling. For working into small wares, up to two gallon jars 

 and crocks, in the jollies, it is far preferable to turned clay. 



In order to test the amount of impurities removed by the washing 

 process, analyses were made of the same clay, both ground and washed, 

 at the plant of the Zanesville Stoneware Co. The figures are given in 

 No. 4 and No. 5 of the table. In this case the chemical changes produced 

 amount to nothing. There is no doubt however that some clays do con- 

 tain impurities which are largely removed by this treatment. The salts 

 of the alkalies do not seem to be affected by washing, which proves that 

 they must be present as insoluble silicates. The highest potash per cent- 

 found in the table (No. 10) is from a washed clay. 



The qualities of ground clay which make it useful are its toughness 

 and strength. There is a structure to the original clay which washing 

 destroj^s, and which grinding only develops. For ware to be made by 

 hand by the spinning or turning process, this is a very important thing- 

 Ground clay is just as impure as the natural clay and fuses just as readily, 

 but on account of its more open structure, it is safer in the kiln. For 

 large ware, from two gallons up, t is almost a necessity, as it stands up so 

 much better. 



The cost of washing clay varies greatly, according to the quantity 

 which the press is required to do. To operate a 72 leaved press, to its 

 maximum is the labor of two (2) men. They can take out five presses a 

 da}-, or about 14,000 pounds of clay. This is at the rate of thirty six cents per 

 ton. By increasing the number of presses and subdividing the labor the 

 price may be reduced. If steaming the blunger increases the speed of the 

 operation as it is claimed to do, the cost could be materially reduced. Twen- 

 ty five cents per 2.000 pounds would be a low figure for the cost of washing 

 and fifty cents is much nearer the average. The cost of grinding is difficult 



