THE POTTERY INDUSTRY. 297 



Analyses of washed Kaolins. 



1. 2. 3. 4. 5. 6. 7. 8. 



Silica (SiCXO, 46.278 45.70 46.50 50.96 48.26 47.71 46.87 59.42 



Alumina (Al 2 O s ), ... 36.25 40.61 37.40 33.30 37.64 36.78 38.00 27.15 

 Ferric oxide (Fe-Os), 1.644 1.39 0.80 0.82 0.46 .... 0.89 1.77 



Lime (CaO), 0.192 0.45 Tr 0.06 Tr 



Magnesia (MgO), ... 0.321 0.09 .... 2.42 Tr 0.35 0.52 



Alkalies (Na20, K2C 1 ), 2.536 2.82 1.1 1.56 2.58 1.22 01.50 



Water (H-O), 13-535 8.98 12.49 8.95 12.02 13.03 12.70 9.85 



a All potash (KX>.) 

 1, Brandywine Summit, Pa. ; 2, Harris Clay Company, near Webster, N. C. ; 

 3, West Cornwall, Conn. ; 4, Glen Loch, Pa. ; 5, Cornwall, England ; 6, Coussac- 

 Bonneval, France; 7, Zettlitz, Bohemia; 8, Pilsen, Bohemia. 



• MANUFACTURE OE POTTERY. 



In making pottery there are certain steps that are common to 

 all grades of ware, but the care of preparation, and the number of 

 steps is increased in the manufacture of the higher grades. 



The different steps may be grouped as follows : 



f Washing. 

 Preparation, j Weathering . 



r Chaser mills. 



Tempering, J Pug mills. 



(Tables. 



, Turning. 



MU . Jollying or jigging. 



Molding, J n ,. 



i Lasting. 



[ Pressing. 



Drying. 



Burning. 



Glazing. 



Decorating. 



Clay is sometimes exposed to the weather as a preliminary 

 means of preparation, but the custom is not a widespread one. 

 High-grade clays are usually freed from grit and sand by a wash- 

 ing process (see Chap. I). 



Tempering. 



Chaser mills are sometimes used at stoneware factories, but 

 none are in operation in New Jersey. They consist of a circular 



