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 (Vitrified)

That degree of vitrification evidenced by low water absorption. (See also Impervious; Nonvitreous; Semivitreous.) (ASTM C 242). NOTE: The term vitreous generally signifies less than t).5 per rent absorption, except for flour and wall tilt and lucvvoltage electrical porechtin which are considered vitreous tip to 3.0 t)er cent water adtsorption.

Vitreous slip

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

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.