Earthenware. 603 



is considered by the manufacturers as a great secret ; they required 

 intimate mechanical mixture of the materials it procured, and the su- 

 perfluous water in the fluid pulp is evaporated in a cistern called the 

 slip kiln, to which heat is applied. 



18. The slip thus reduced to a pasty mass is removed, and is 

 stored for many years in chambers on stone floors, where it is pro- 

 bable some chemical reaction goes on between the component earths, 

 by which they are better fitted to react upon each other in the firing. 

 Indeed it is almost certain, that such reaction has place, because 

 in some of the mills in which the slip is very finely ground between 

 two horizontal stones for the manufacture of Porcelain, the stones 

 when allowed by accident to remain at rest for an instant, are 

 so firmly cemented together, as to resist the action of a very consi- 

 derable force to separate them again. 



19. The evaporated slip now called clay is then " wedged," by 

 beating it with mallets, and cutting into pieces with a spade, by 

 which all the air bubbles it contains are dislodged; or in large 

 works, a machine with revolving knives, which alternately cut and 

 press it, produces the same effect. 



20. The clay is then taken by the " thrower," who first subjects 

 it to the operation called " slapping," by which any remaining air 

 bubbles are completely dislodged, and it is then stuck upon the apex 

 of the "potter wheel," and is fashioned, while revolving, by the 

 naked hands, into the form of the vessels required. 



21. The clay having been "thrown" into the rough form of the 

 vessel, it is allowed to dry for a short time, and being then in what 

 is called the " green state," it is fixed in a lathe, and turned with 

 tools, or rather scraped into a correct form. 



22. "When the vessels required are of irregular figures, or are orna- 

 mented, they are formed by squeezing or " pressing" the clay between 

 moulds made of Plaster of Paris, and the handles, spouts, &c. are 

 formed in the same way, and are stuck on with a little soft "slip." 



23. The ware is then put in cases of infusible materials call- 

 ed " seggars," and is fixed in what is called the biscuit oven, so 

 named from the appearance of the ware after its removal, in 

 which state it is fitted to receive and imbibe colours, prints, or pain- 

 tings. 



