The subject of "Grand Feu Ceramics" has been so ably developed by M. Taxile Doat in his admirable treatise[P] that it will be unnecessary to go deeply into the matter, but in order that the reader may be aware of what is involved, some description of the technique will be given.
[P] Keramic Studio Publishing Co., Syracuse, N. Y.
Hard-fired wares are divided into two classes, porcelain and stoneware. The latter is called by the French, "Grès," an abbreviation of the name "Grès de Flandres," the stoneware made in the low countries in the sixteenth century. Both these wares are, technically, once fired, that is, the body and glaze come to maturity at one and the same burning. The biscuit ware is often given a low burn at first in order to facilitate handling, but this leaves the body very porous and is in no sense a maturing fire. The glaze is laid upon this porous ware, or upon the unburned clay if preferred, and then comes the high fire or "Grand Feu" of the French.
A mix for a porcelain body has already been given but if the ceramist means seriously to attack the porcelain problem he will have to do some experimental work for himself. The Georgia kaolin mentioned in the recipe on page 40 is a good, plastic clay but it is slightly off color. It may be necessary to improve the color by the use, in part, of another kaolin such as the Harris clay from North Carolina.[Q]
[Q] The Harris Kaolin Company, Dillsboro, N. C.
Furthermore, in the preparation of a fine porcelain it is necessary to grind the whole mix upon a mill. The mill used for glaze grinding will answer every purpose and care must be taken that the grinding, while carried far enough, be not too long continued. A certain amount of fine grit in the body mass is necessary but only by constant practice can the right point be reached. In making these experiments each step should be faithfully noted in a handy book. The amount of water to a given weight of clay and the duration of the grinding should be accurately observed and written down. It is most unwise to trust to memory.
The process of casting may be used for porcelain as already described, but the very best of workmanship is necessary. The hard fire to which the porcelain is subjected reveals every error which has occurred in the making. The same thing applies to wheel work. Not only is great skill required in order to shape the tender porcelain clay on the wheel but the very essence of the porcelain is its lightness, to produce which by craftsmanship a long and arduous course of training must be endured.