THE POTTERS ART. 



allowed to stand for a sufficient time, all the fine matter suspended 

 in it at length subsides to the bottom, the water becoming clear 

 above. This water is then allowed to now off, when a stratum of 

 fine and pure petung-tse is found on the bottom of the trough. 

 This is then consolidated and formed by moulds, as represented in 

 the background of fig. 17, into bricks, in which state it is sent to 

 the potteries. 



2. This mineral substance, which plays a part so important not 

 only in the Chinese potteries, but in those of other nations, is a 

 variety of that which mineralogists have called felspar, having a 

 slight admixture of quartz. 



3. The PETUNG-TSE thus prepared is a white substance of the 

 finest imaginable grain, about two and a half times heavier than 

 water. 



The other material used in the formation of the dough or paste, 

 of which the Chinese make their porcelain, called KAOLIX, is 

 found in very deep strata of some of their mountains, and took its 

 name from a mountain near King-Te-Tschin, where the first vein 

 of it had been discovered, which was the origin of the great pottery 

 works established at that place. 



The manner of working and purifying the kaolin and forming 

 it into bricks for the potter, does not differ in any important par- 

 ticular from the treatment of petung-tse already described. 



Kaolin, when submitted to chemical analysis, proves to be a 

 compound body whose constituents are silica, and alumina, or the 

 pure earth of clay combined with small proportions of magnesia, 

 potash, soda, and iron. 



The earths called kaolin or china clay include these constituents 

 in very different proportions as found and used in different 

 countries. That used in the fabrication of the old Chinese porce- 

 lain contains 76 per cent, of silica, from 10 to 17 per cent, of 

 alumina, and small proportions of magnesia, potash, and soda. 



The Chinese consider that it is to the kaolin that the ware owes 

 all its strength. They call it the nerve of the porcelain, meaning 

 probably the plasticity of the paste and its power to resist the 

 intense heat of the furnace. Hearing of the attempts of the 

 European potters (before their discovery of china clay) to make 

 porcelain of petung-tse or felspar alone, they ridiculed the attempt, 

 observing that " they might as well attempt to make a body of 

 flesh without bones." 



This alludes plainly enough to the comparatively easy fusibility 

 of petung-tse, and the infusibility of kaolin by the porcelain 

 furnaces, and it would even indicate the probability that the 

 Chinese themselves had tried and abandoned the manufacture of 

 porcelain without kaolin. 

 130 



