The polychrome types include youshang hongcai (wares painted with iron-red over the glaze),
qinghua hongcai (wares combining underglaze blue and overglaze iron-red decoration),
doucai (wares with an underglaze-blue outline of the design filled in with overglaze enamels),
and wucai (wares decorated in overglaze enamel colours). A variant of wucai is the use of
underglaze blue notmerely for outlining, as in doucai, but as part of the decorative scheme
with overglaze enamels. This may be called, strictly speaking, qinghua wucai. All these
polychrome types involved two firings: the first at a high temperature of around 1,100C for
the paste, the underglaze blue painting where applicable, and the transparent white glaze;
the second, at a lower temperature of around 850C in a muffle kiln, in order to fuse the
overglaze enamels to the glazed porcelain. Gilding technique was most popular during
the reign of Jiajing.