GERMAN MANUFACTORIES. 



having the qualities necessary to render it a tolerable substitute 

 for the fine china clay, directed all their efforts to invent some 

 artificial composition which might serve the purpose and enable 

 them to compete with foreign potters. 



The result was the invention of an artificial imitation of the 

 porcelain paste, which soon became the basis of a great manufactory 

 in France, and which continued for half a century to be known as 

 the pate tendre of the Royal manufactory of Sevres. 



This material did not contain a particle of kaolin or felspar, 

 the essential constituents of all genuine porcelain. Its composition 

 was subject from time to time to slight variations ; for, for the best 

 porcelain, it consisteu ,t' the following constituents in an hundred 

 parts by weight : 



Fused nitre (mineral crystals) ... 22 '0 



Grey sea-salt 



Alum ...... 



Soda of Alicant .... 



Gypsum of Montmartre (plaster of Paris) 

 Sand of Fontainbleau 



7-2 

 3-6 



3-6 



3-6 



60-0 



100-0 



These materials being well mixed, were fritted either in the 

 porcelain oven, or in an oven expressly appropriated to this process. 

 It was usual, however, to calcine the alum and the gypsum pre- 

 viously to disengaging their water of crystallisation. 



The dough called the pate tendre, was formed by the mixture of 

 this frit with white chalk and calcareous marls from the gypseous 

 earth of Argenteuil, in the following proportions by weight : 



Frit 75 



Chalk 17 



Gypseous earth 8 



100 

 The whiteness and consistency or hardness of this dough was 



modified by varying the proportion of chalk. 



All these materials were intimately kneaded together, bruised 



with water in a mill, and in fine passed through silken sieves. 

 The glaze used for this factitious biscuit was composed as 



follows : 



Litharge 38 



Calcined sand of Fontainbleau . . . . 27 



Calcined silex 11 



Sub -carbonate of potash. . . . 15 



Sub-carbonate of soda 9 



100 



31. This paste after all was so utterly wanting in plasticity and 



159 



