For sanitary pipes and chemical stonewares,

ANS:A - salt glazing is used

Salt glazing.

The wet salt is vaporized and the vapor formed is of sticky nature. This salt vapor forms a glass-like layer on the surface of a clay product. The salt glazing generally produces brownish color on the product. Stoneware products, sanitary pipes, etc are glazed by this method.

How do you make salt glaze for pottery?

When salt-glazing pottery, unglazed wares are placed in the kiln and heated to a very high temperature. At that point, salt is thrown into the hot kiln; the salt vaporizes, fuming throughout the kiln interior, and combines with the clay of the pottery, forming a natural glaze on all the pots.