Jasper Ware es como una suave porcelana con sulfato de bario, arcilla y porcelana
La composición de Wedgwood Jasper se da como:
- 18 China arcilla o caolín,
- 26 ball clay
- 11 Flint
- 45 Barium Sulphate Burning at Cone 10/11. [1]
More popularly known as Wedgwood ware, differs from pate-sur-pate in the method of applying the clay, which is usually white clay squeezed into moulds and then withdrawn to be attached to the surface of the body of the vases ; the ware is not glazed ; it has no more vitreous appearance than is produced by the hard fire on the mixed clay body, and pre- sents a dead texture. The ground may be of any color. Josiah Wedgwood invented jasper ware, and the firm of Wedgwood & Co. is constituted by his descendants. [2]
Although Wedgwood ware presents less varied and subtle effects than pate-sur-pate, yefc the outline of the relief is generally more perfect. Most of the designs used by Wedg- wood & Co., are Flaxman's; and the beauty of their ware with blue, dove, or olive colored ground is well known. Jasper ware may be defined as a superior quality of vitrified stone-
ware. It requires more careful preparation, and is formed of a plastic clay to which vitrifying ingredients such as Cornish stone, flint, ground glass, felspar, sulphates and carbonates of lime and of barytes (L. Arnoux) have been added.
According to Salvetat fine yellow Wedgwood ware consists of:
Silica 66.49.
Alumina 26.
Oxide of iron 6.12.
Lime 1.04.
Magnesia .*. 0.15.
Alkalies 0.20.
White jasper ware contains variously 15 to 30 per cent, of plastic blue clay, to 15 kaolin, to 15 Cornish stone, or, summing up, 40 to 50 per cent, of these clay materials ; to which is added 25 to 45 per cent, heavy spar, to 10 flint, and to 2 gypsum. Sometimes 20 per cent, calcined bone is introduced. This white body may be differently colored by metallic oxides, ^ per cent, cobalt giving blue, with 1 per cent, chrome dark green, nickel light green, copper bluish green.
From natural ochreous clays and quartz a reddish por- phyritic jasper ware is made.
Basalt ware, susceptible of high polish, and Egyptian ware are made by introducing in the body some 40 per cent. of burnt ochre, or 16 per cent, ochre and 45 of red clay, and sometimes 10 per cent of mill cinder (iron).
