Page 178 - Chinese pottery and porcelain : an account of the potter's art in China from primitive times to the present day

100 Chinese Pottery and Porcelain

of It oz. of antimony mixed with 16 oz. of pulverised lead ; bright
green {chin lu), composed of If oz. of pulverised copper, 6 oz. of

powdered quartz and 16 oz. of pulverised lead purple {tzu sS),
;

composed of 1 oz. of cobaltiferous ore of manganese, 6 oz. of pow-

dered quartz and 16 oz. of pulverised lead. These colours, melting

as they did at a lower temperature than that required to vitrify

the porcelain body, had to be applied to an already fired porcelain
" biscuit." 1

The irregular construction of the Chinese kilns resulted in a

great variety of firing conditions, of which the Chinese potter made

good use ; so that, by a judicious arrangement of the wares, glazes

which required a comparatively low temperature were fired in the

same kiln as those which needed the same heat as the porcelain

body itself. The glazes just enumerated are familiar from the

large covered jars, vases, garden seats, etc., with designs raised,

carved, or pierced in outline, many of which date from the fifteenth

century.^ Their manufacture continued throughout the Ming period,

both in porcelain and pottery, and in the latter, at any rate, con-

tinued into the Ch'ing dynasty.

Another group of glazes applied likewise to the biscuit and fired

in the temperate parts of the kiln differs from the last mentioned

in its greater translucency.^ These are the san ts'ai or three colours,

viz. green, yellow and aubergine, all of which contain a considerable

proportion of lead, and differ little in appearance from the on-glaze

enamels of the muffle kiln. They were used either as monochromes,

plain or covering incised designs, or in combination to wash over

the spaces between the outlines of a pattern which had been

incised or painted on the biscuit.

WanFinally, the enamels of the li wu ts'ai,'^ overglaze colours

used in addition to underglaze blue, were composed of a vitreous

flux coloured with a minute quantity of metallic oxide. The flux,

being a glass containing a high percentage of lead, was fusible at

such a low temperature that it was not possible to fire them in the

large kiln. Consequently these enamels were painted on to the

finished glaze, a process which greatly increased the freedom of

^ Biscuit is the usual term for a fired porcelain which has not been glazed.

2 See p. 17.
^ It has been suggested by Mr. Joseph Burton that the opacity of the colours described

in the preceding paragraphs may have been due to the addition of porcelain earth to

the glazing material.
* See p. 82.