INGENUITY AND LUXURY 



a lower temperature than the ware it covers, and at 

 the same time have the property of expanding and 

 contracting in the same ratio, or otherwise fine cracking, 

 or "crazing" as it is called, will result. This last is 

 considered one of the greatest defects in earthenware, 

 although it is sometimes produced intentionally by 

 Chinese potters in making ornamental pieces. Crazed 

 pieces, such as table dishes, that must be put to hard 

 usage, become discolored and eventually fall to pieces. 



When we consider that the glaze is a composite of 

 several different substances, each with a different 

 expanding ratio; that the mixture itself will have a 

 still different expanding ratio, which changes with 

 the varying quantities cf the substances it contains; 

 and that this same thing is true of the body-substance 

 of the ware, it seems almost a hopeless task to attempt 

 to produce the right combination of the two. Yet 

 the potter has solved this in a most practical and eco- 

 nomical way, as witness the quantities of good china- 

 ware now placed upon the market at a price within the 

 reach even of the very poor. But what an expenditure 

 of time, thought, and material wasted in experiments, 

 the cheap little cup on the table of the humble laborer 

 represents! 



The dry materials generally used for glazes are china- 

 clay and flint. These are combined in varying pro- 

 portions with "fluxing materials," such as carbonate of 

 lime, carbonate of potash, carbonate of soda, carbonate 

 or oxide of lead, china-stone, tincal, boric acid, and 

 borax. Some of these are soluble in water, and as 

 the glaze is applied as a liquid, it is necessary to vitrify 



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