STONEWARE is that kind of earthen ware (see CERAMICS) which is impervious to water and non-absorbent, almost non-porous, the whole substance of the paste being very silicious, either from the original nature of the clay or from a mixture with the clay of some natural silex such as flint. A simple test is that a broken fragment, if put to the tongue, will not seem to cling to its surface; whereas a broken flowerpot will cling tenaciously, this being caused by the rapid absorption of moist ure by the porous substance. It is for this reason that stoneware is used for acid contain ers, bottles, vinegarjugs and all such common purposes, and also for larger and more deco rative vessels in countries and in times where it is customary to use earthenware vessels in stead of glass or metal at least to a great ex tent. Thus in the Rhine towns and north western Germany during the 14th and follow ing centuries a very elaborate series of cans, jugs and flagons of all sizes from a pint to three or four gallons, were made and decorated by simple impressions from metal or wooden dies impressed upon the surface before firing; the pattern being afterward more or less em phasized by a thin glazing of blue applied in parts. The glaze of stoneware in the usual sense is no more a separate substance than that of Greek vases; it is a mere modifying of the i surface generally by some vaporized ngredi ent which is absorbed during the actual process of firing. Thus the most common glaze, called salt-glaze, is generally understood to be pro duced by throwing into the furnace rough salt, which is vaporized and leaves the soda in its composition on the surface of the stoneware in the form of a slight, glassy film. The stone
ware would not need this to be sufficiently re sistantagainst water, wine or the like, but some acids would attack the stoneware, against which the glaze is a sufficient protection.
These decorative wares have been known to the collectors, and in museums and in treatises on Ceramics under the general name of gres de Flandre, as if they were of Flemish make, but this term is now replaced by such terms as Cologne Ware, German Stoneware and the like. In modern times stoneware has not been gen erally used for decorative purposes; but recent experiments in the national manufactory of porcelain at Sevres in France have led to the invention or adoption of many brilliant colored enamels which can be applied to stoneware with out in the least diminishing its value as a dur able and weatherproof material; and in this way a whole class of architectural ceramic wares has been made practicable. Magnificent specimens of these wares — even to the extent of huge friezes containing many figures, were on exhibition at Paris in 1900 and any future attempts at decorative architecture will have to include the consideration of these new means of brilliant adornment in color and in form. See POTTERY.