INGENUITY AND LUXURY 



nically called. The stain is an oxide of cobalt 

 beautiful deep blue which is not affected by heat. 

 A sufficient quantity of this is mixed in the "body" 

 to neutralize exactly the yellow stain of the iron, so 

 that the ware will be pure white, just as bluing is used 

 in laundries for whitening linen. 



The principal source of cobalt to-day is Hungary, 

 although it is found in many other countries, and has 

 been used for centuries by Egyptian, Chinese, Ara- 

 bian, and other potters. The purest form of cobalt is 

 obtained as a by-product of nickel. It must be ground 

 to impalpable fineness before using in pottery, or other- 

 wise small blue specks will appear, as may be seen 

 frequently in the cheaper forms of earthenware. 



It is apparent, even from this brief description of 

 the processes preliminary to the manufacture of pot- 

 tery, that there is a wide gap between the work of the 

 primitive potter who molded a handful of clay and 

 placed it in his fire, and the modern scientific methods 

 that have developed from this simple process. Yet 

 in all the succeeding steps in the manufacture of the 

 ware there are quite as wide gaps, which have been 

 bridged by modern chemistry and mechanics. 



MIXING THE MATERIALS 



The first step to be taken in the manufacture of 

 pottery is that of mixing the prepared products in the 

 proportions required. Two of these mixtures are 

 necessary, one for the "body," the thick substance of the 

 ware itself; the other for the "glaze" or thin coating 

 of vitreous substance covering it. 



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