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jasperware
Jasperware, or jasper ware, is a type of pottery first developed by Josiah Wedgwood in the 1770s. Usually described as stoneware, some authorities have described it as a type of porcelain.〔
*PaulRado. ''An Introduction To The Technology Of Pottery.'' 2nd edition. Pergamon Press / Institute Of Ceramics. 1988.〕 It is noted for its matte finish and is produced in a number of different colours, of which the best known is a pale blue that has become known as Wedgwood Blue.〔Wedgwood blue on Wiktionary〕 While named after the mineral jasper, modern analyses indicate that barium sulphate is a key ingredient.〔(Jasper Wedgwood – A Brief History )〕 Wedgwood had introduced a different type of stoneware called black basalt a decade earlier.
==Jasperware composition and colours==
Jasperware's composition varies but proportions may be given as follows: sulphate of barytes 150, china clay 35, blue clay 45, flint 35, gypsum 6, and Cornish stone 50.〔''Chemistry, Theoretical, Practical, and Analytical: As Applied and Relating to the Arts and Manufactures'', Volume 2, Glasgow : Mackenzie, 1860, by Sheridan Muspratt, Eben Norton Horsford, and William Mackenzie, page 817.〕 It is white by nature but stained with metallic oxide colors; its most common shade in commerce is pale blue, but dark blue, lilac, sage green, black, and yellow are also used, with sage green due to chromium oxide, blue to cobalt oxide, and lilac to manganese oxide, with yellow probably coming from a salt of antimony, and black from iron oxide.〔()〕 The earliest jasper was stained throughout and was known as "solid," but by 1829 production in jasper had virtually ceased. In 1844 production resumed using items coloured only on the surface and known as "dip." Solid jasper was not manufactured again until 1860.〔()〕
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