The material most commonly used for the cheaper kinds of fittings is salt-glazed stoneware. The glaze is produced by throwing common salt into the kiln during the last stage of firing. The salt is decomposed by the heat and fills the kiln with dense fumes of salt-vapour, which enter into chemical combination with the silica on the surface of the clay, producing a thin glaze of silicate of soda; the glaze is, therefore, a portion of the stoneware itself, fused or vitrified under the influence of salt. A salt-glaze has the advantage of being thoroughly incorporated with the material to which it is applied. On the other hand, it is not very smooth, as roughnesses or inequalities in the plastic clay are still apparent in the finished production. The colour of salt-glazed ware is generally some shade of reddish brown, more or less mottled, but an amber glaze can now be obtained, and has a much cleaner appearance.

All pottery is somewhat brittle, and sharp corners may be chipped off by a blow, even though glazed. For this reason all external angles ought to be rounded.

Salt-glazed stoneware is largely used for the cheaper kinds of sinks, urinals, school lavatories, latrines and water-closets, and also for heavy fittings for factories and other places where rough usage is likely to occur, as well as for drain-pipes and traps. It varies in smoothness, toughness and density, according to the nature of the clay and the skill exercised in its manufacture.