RECENT ADVANCES IN THE POTTERY INDUSTRY. 299 



which was held by the water in suspension, upon the surface of 

 the piece. This piece of porous biscuit covered with glaze is now 

 cleaned of glaze upon its foot, or that part upon which it rests, to 

 prevent its sticking or burning fast to the clay " sagger " or firing 

 case ; otherwise the glaze on the bearing parts would, at the time 

 of flowing, form a cement, fastening the piece and the sagger 

 together. The pieces are placed separately in the saggers. The 

 heat in firing hard porcelain is carried to such a high degree that 

 the ware touches the point of pliability, almost the melting-point. 

 At this point of heat the body is vitrified ; at the same time the 

 glaze, from its slightly softer composition, is melted into the body 

 of the ware, producing 

 a hard, vitreous, and 

 homogeneous material 

 properly known as true, 

 hard porcelain. This 

 is the process used at 

 Sevres, Meissen, Berlin, 

 and elsewhere. 



The earthenware 

 method is just the re- 

 verse of this. The body 

 is composed of much the 

 same materials as a por- 

 celain body, but difiier- 

 ently compounded, and 

 it is baked in biscuit at 

 the first firing at a great- 

 er heat than is required 

 for porcelain biscuit, 

 and receives during that 

 first burning the great- 

 est heat to which it is 

 subjected in the entire 

 process of manufacture. 

 The glaze is composed 

 partly of the same ma- 

 terials as compose the 

 body, with the addition 

 of oxide of lead and boracic acid, which latter, being soft, fluxes 

 in the fire, enabling the glaze to flow at a low heat. It is fired 

 the second time in the gloss-kiln at a lower temperature than 

 it has previously been fired in biscuit. This results in flowing 

 the soft glaze over the surface of the ware, making sul)stan- 

 tially a lead-glass film or coating upon the surface of difi'erent 

 compounds and materials, not homogeneous, not a part of the 



Fig. 27. 



-BrsT or Edwin Forrest as William Tell. 

 Union Porcelain Works. 



