Glossary of Industry Terms


Vapor barrier

Waterproof membrane placed under concrete floor slabs that are placed on grade.

Vellum glaze

A semi-mat glaze having a satin-like appearance. (ASTM C 242).

Vertical broken joint

Style of laying tile with each vertical row of tile offset for half its length.


–0.5 percent to 3 percent water absorption.

Vitreous slip

A slip coating matured on a ceramic body, producing a vitrified surface. (ASTM C 242).

Vitreous (Vitrified)

That degree of vitrification evidenced by low water absorption. (See also Impervious; Nonvitreous; Semivitreous.) (ASTM C 242). NOTE: The Wrn vitreous generally signifies Icss than 0.5 per cent absorption, except for floor and %wall tile and lowvoltagc electrical porcelain which ore considered vitreous tip to 3.0 per cent water absorption.

Vitreous tile

Tile with water absorption of more than 0.5 percent, but not more than 3.0 percent. (ANSI A137.1-1980).


The progressive reduction in porosity of a ceramic composition as a result of heat treatment, or the process involved. (ASTM C 242).

Vitrification range

The maturing range of a vitreous body, producing a vitrified surface. (ASTM C 242).


An unfilled space in a material of trapped air or other gas.