ENGLISH PORCELAIN. 



r -tains its form, just as a porous vessel such as a flower-pot would, 

 if it were thoroughly saturated with water. The semi- transparency 

 of porcelain thus produced is an effect of the same class as that 

 imparted to paper or linen cloth by saturating it with melted wax. 

 The vitriliable constituent which thus renders porcelain trans- 

 lucent is generally the felspar ; in some cases, however, it is lime 

 which, entering into combination with the alumina and silica of 

 the clay, forms a double silicate of alumina and lime, more fusible 

 still than the simple silicate of alumina. The oxide of iron pro- 

 duces a like effect, but as it gives a colour to the paste, it can only 

 be used in the commoner sorts of ware. By increasing the propor- 

 tion of the vitritiable constituent, greater translucency is imparted 

 to the ware, but the body becomes less plastic, more liable to dis- 

 tortion, and more difficult to work. 



13. It is most necessary to comprehend the distinction between 

 the hard porcelain, the manufacture of which, as we have stated, 

 was carried on at a very early date in the East, and the varieties 

 of tender porcelain. The body of the latter sorts is more fusible than 

 that of the former. This property is given to it by introducing 

 into it a larger proportion of alkaline constituents, either in the 

 form of felspar, or of alkaline silicate, prepared expressly for the 

 purpose, and called frits. The glaze used for these porcelains is 

 also more fusible than that of hard porcelain, a quality which it 

 receives from a certain proportion of the oxide of lead which enters 

 into its composition. 



In certain sorts of tender porcelain no clay whatever is used, and 

 the entire body consists of an artificial frit. Such ware, however 

 beautiful it may be rendered in external form and appearance by 

 tine workmanship and rich ornamentation, cannot properly be 

 called porcelain at all. It is at best only an ingenious imitation of 

 that article, bearing to it the same relation as a gilded article bears 

 to a gold one. Nevertheless, such is the article so much admired 

 and so highly prized under the denomination of the " Old Sdvres 

 Porcelain." 



14. The English porcelain, and certain sorts still produced in 

 some of the private manufactories of France, belong to the class of 

 tender porcelain, though not all identical with, or even resembling, 

 the Old Sevres Porcelain. The English porcelain is composed chiefly 

 of clays found in Cornwall, Devon, and Dorsetshire. The Cornish 

 is the best quality, and is technically termed by potters "china 

 clay ; " it enters very extensively into the composition of the best 

 kind of ware. It is the decomposed felspar of the granite, and is 

 prepared by the clay merchants themselves in Cornwall, prior to its 

 being sent to the potteries. Huge masses of white granite abound 

 in Cornwall, which is in some parts found partially decomposed ; 



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