Cracked porcelain.—The To-wi-kie China-ware is highly prized under the cognomen of cracked porcelain. It is prepared simply by varnishing the vessels with a whitish ash-coloured varnish, made from calcined transparent white pebbles. This has the property of marbling and veining the ware, and giving it an appearance as if it had been fractured into many pieces, which had been carefully reunited.
Chinese red colour, used in the porcelain paint ing, is made from Taow-fau, or copperas. Their mode of perparation is by putting a pound of copperas into a crucible, over which another crucible is luted, having a small hole in it, which is lightly covered over ; around these they pile charcoal, and enclose the whole within bricks, when they fire the charcoal, and as soon as the fumes issuing from the aperture in the crucible become of a light colour, a small quantity of the copperas is taken therefrom, laid upon fir-wood, and moistened with water ; if the colour then prove to be a bright red, they remove the fire, if not, they allow the copperas to remain subjected to the heat until it assumes that colour, and then remove the fire. When the crucibles are cool, a cake is found in the lower one, but the finest colour is encrusted on its sides and on the bottom of the upper crucible, which is kept separate from the cake ; the pound of copperas produces about four ounces of colour.
Chinese white colour, also used in painting porce lain, is made from calcined transparent flint, to an ounce of the powder of which they add an equal quantity of white. lead.
Chinese green, a beautiful colour, is prepared with one part of powdered calcined flint, two parts of white lead, and six parts of the scales of well-hammered copper.
Chinese violet is produced by adding an ad ditional quantity of the prepared white to the green.
Chinese yellow is made by combining equal portions of prepared white and red..
All these various colours are used by the China ware painters, having been previously dissolved in gum-water, to which they occasionally add salt petre, copperas, or white lead. The colours are laid on after the first baking and varnishing of the China-ware, but the beauty and depth of the colouring is imperceptible until after the second baking.—Williams' Middle Kingdom, ii. p. 116. See Ceramic Manufactures; Earthenware ; Pottery.