China-clay of Cornwall. 101 



are mixed together in variable proportions in a large vat or 

 tub, and, as soon as the mixture has attained its requisite 

 consistence, the water is driven off by evaporation, which 

 causing the slip to contain in its interstices an innumerable 

 quantity of air globules, renders it necessary that it should 

 be submitted to the process of kneading or beating, after 

 which it was formerly thought necessary, though now aban- 

 doned, that this mass should lie fallow for three or four 

 months, when it is considered to be fit for the lathe. 



The proportions of the ingredients used in the different 

 kinds of earthenware are as follow : — 



In cream colour or painted ware, — Dorsetshire clay, 56 

 parts ; kaolin or China-clay, 27 ; flint, 14 ; and China- 

 stone, 3 parts. 

 In brown ware, — red clay, 83 ; Dorset clay, 13 ; flint, 2 ; 



and manganese, 2 parts. 

 In drab ware, — Cane marl, 32 ; Dorset clay, 22 ; China- 

 stone, 45 ; and nickel, 1 part. 

 In jasper, — barytes, 32 ; kaolin, 15 ; Dorset clay, 15 ; 



stone, 33 ; and of lead, 3 parts. 

 The glazes commonly used for the cream-coloured ware 

 consists of varying proportions of white lead and China- 

 stone, or, as these may craze, a frit of the following materials 

 is often employed : — 



Of China-stone, 30 ; flint, 16 ; red lead, 25 ; soda, 12 ; 

 and borax, 17 parts ; 26 parts of this are then mixed 

 with 15 of China-stone, 10 of flint glass, 9 of flint, and 

 40 of white lead ; which constitutes the fritted glaze. 

 The composition of most of the bodies and clays now used 

 is a secret confined to the walls of the mixing room, so that 

 it is extremely difficult to ascertain, with any degree of ac- 

 curacy, the influence of an excess of ingredients ; thereby en- 

 tailing a co-existent difficulty on the part of the producer, in 

 his endeavour to form or prepare a substitute for these 

 articles. 



The China-clay or kaolin of Cornwall was first brought in- 

 to notice at a very late period, though the material itself has 

 been long used ; in fact, not only were the Chinese well ac- 



