xiv Portraits, Medallions, Artistic Work 153 



of treatment where any marked degree of translucency 

 in the material used for the reliefs was of decided 

 disadvantage ; here the more opaque varieties of the 

 jasper body were preferred. The smoothness of surface 

 which this ware, as made by Josiah Wedgwood, almost 

 invariably possessed, is delightful at once to the senses 

 of touch and sight, and, moreover, it affords one of the 

 best criteria for distinguishing old work from new. It 

 was caused chiefly by the extreme fineness to which 

 the components of the jasper body were reduced, but 

 the exact adjustment of the temperature of firing the 

 ware to its composition doubtless influenced the result." 



This material was called jasper from its resemblance 

 to that stone. The jasper ware was made of white 

 porcelain bisque, and was susceptible of receiving 

 colours throughout its whole substance, but more 

 especially of being stained with fine mazarine blue. 

 This property of receiving colours, which no other 

 body, either ancient or. modern, has been known to 

 possess, rendered it peculiarly fit for cameos, portraits, 

 and all subjects in bas-reliefs, as the ground may be 

 made of any colour throughout, the raised figures being 

 of a pure white. 



"The peculiarity in chemical composition," says 

 Professor Church, " which marks out the jasper ware 

 body from all other ceramic pastes, was brought about 

 by the introduction of a compound of the element 

 barium." This is chiefly found in the form of sulphate, 

 the mineral being found abundantly in Derbyshire, 



