CLAYS OF WEW YOKK 803 



most of the clear water is drawn off; tlie cream-like mass of kaolii). 

 and water in the bottom of the vat is drawn off by means of slip 

 pumps and forced by these into the presses. 



The presses consist simply of flat, iron or wooden frames be- 

 tween which are flat canvas bags. These bags are connected by 

 nipples with a supply tnbe from the slip pumps, and by means of 

 the pressure from the pumps nearly all of the water is forced out of 

 the kaolin and through the canvas. When as much water as pos- 

 sible is squeezed out, the press is opened and the sheets of semi- 

 dry kaolin are taken out. It is then dried either on racks in the 

 open air or in a steam-heated room. 



As for every ton of crude kaolin usually only about |- or |- of 

 a ton of washed kaolin is obtained, it is desirable to have the wash- 

 ing plant at the mines, to avoid the hauling of 60 fo to TO^ of useless 

 sand which has to be washed out before the kaolin can be used or 

 even placed on the market. 



Tempe7'ing 



Chaser mill. This consists of a circular iron pan in which 

 revolves a frame bearing two heavy iron wheels, about 30 to 36 

 inches in diameter. As this frame revolves, the wheels, by means of 

 a gearing, travel from, the center to the circumference of the pan 

 and then back. The clay is dumped into the pan, water added, 

 and by the action of the wheels, grinding and cutting it up, it is 

 ground and mixed in from one to two hours. The action of such a 

 machine is quite thorough, but requires considerable power to 

 operate it. It is sometimes used for stoneware clays. 



Wet pans. The action of these has already been described, 

 under bricks. This machine is occasionally used in the preparation 

 of pottery clays, and is fully as efiicient in its action as the pre- 

 ceding one, while it has the advantage of operating continuously 

 and also of requiring less power. The clay is also ground and mixed 

 much more quickly in a wet pan than in a chasing mill; and the 

 greater width of the wheels, and the presence of scrapers to throw 

 the clay under them, insures the thorough grinding of any lumps 



