Glazing

—A good enamel is an e ential element of fine stoneware; it should experience the same dilatation and contraction by heat and cold as the biscuit which it covers. The English enamels contain nothing prejudicial to health, as many of the foreign glazes do; no more lead being added to the former than is absolutely nece ary to convert the siliceous and aluminous matters with which it is mixed into a perfectly neutral gla . Three kinds of glazes are used in Staff ords hire; one for the common pipe-clay or cream-coloured ware; another for the finer pipe-clay ware to receive impre ions, called printing body ; a third for the ware which is to be ornamented by painting with the pencil. The glaze of the first or common ware is composed of 53 parts of white lead, 16 of Cornish stone, 36 of ground flints, and 4 of flint gla ; or of 40 of white lead, 36 of Cornish stone, 12 of flints, and 4 of flint or crystal gla . These compositions are not fritted; but are employed after being simply triturated with water into a thin paste. The following is the composition of the glaze intended to cover all kinds of figures printed in metallic colours: 26 parts of white felspar are fritted with 6 parts of soda, 2 of nitre, and 1 of borax; to 20 pounds of this frit, 26 parts of felspar, 20 of white lead, 6 of ground flints, 4 of chalk, 1 of oxide of tin, and a small quantity of oxide of cobalt, to take off the brown cast, and give a faint azure tint, are added. The following recipe may also be used. Frit together 20 parts of flint gla , 6 of flints, 2 of nitre, and 1 of borax; add to 12 parts of that frit, 40 parts of white lead, 36 of felspar, 8 of flints, and 6 of flint gla ; then grind the whole together into an uniform cream-consistenced paste. As to the stoneware which is to be painted, it is covered with a glaze composed of 13 parts of the printing-colour frit, to which are added 50 parts of red lead, 40 of white lead, and 12 of flint; the whole having been ground together. The above compositions produce a very hard glaze, which cannot be scratched by the knife, is not acted upon by vegetable acids, and does no injury to potable or edible articles kept in the ve els covered with it. It preserves for an indefinite time the gla y lustre, and is not subject to crack and exfoliate, like most of the Continental stoneware, made from common pipe-clay. In order that the saggers in which the articles are baked, after receiving the glaze, may not absorb some of the vitrifying matter, they are themselves coated, as above mentioned, with a glaze composed of 13 parts of common salt, and 30 parts of potash, simply di olved in water, and brushed over them.