Glossary

W

Walnut Shell
Black walnut shells crushed to provide a hard non-mineral aggregate. Used in conductive troweled systems because of its non-sparking ability.

Wash Primer
A thin paint, usually a chromate, designed to promote adhesion or to be used as a barrier coat.

Water Blasting
Blast cleaning of metal or concrete using high velocity water. See Also “Pressure cleaning,” “Low-Pressure Water Cleaning,” & “High Pressure Cleaning.”

Water Spotting
A surface defect caused by water droplets depositing a circular ring of contaminants.

Water Vapor Permeability
A property of material which is water vapor permeance though unit thickness. Since materials that provide resistance to vapor flow are never used in unit thickness, the preferred evaluation of both materials and constructions is the permeance.

Water Vapor Permeance
The time rate of water vapor flow through unit area of the known thickness of a flat material or a construction normal to two specific parallel surfaces induced by unit vapor pressure difference between the two surfaces under specific temperature and humidity conditions. See perm.

Weatherometer
A machine designed for the accelerated testing of coatings.

Weld Slag
Amorphous deposit formed during welding.

Weld Splatter
Beads of metal left adjoining the weld.

Wet on Wet Application
As high solids coatings continue to grow in popularity, the statement of "wet on wet" application is used regularly. Over the past few years this statement has been used very loosely and its true meaning has been lost or misunderstood by many. As a clarification "wet on wet" is meant to be that the coating is applied in TWO separate coats or applications. Whenever possible contrasting colors should be utilized for the two coats to aid in the application.

Typically the structure is coated with the first coat and the applicator then turns around and begins the second application. As an example, if you have an I-beam or a railcar, the complete structure has the first coat applied before the second coat begins. Depending upon what is being coated the time between coats will vary dramatically. The key to the whole concept is that it is two independent coats. By applying the coating in two distinctive coats or applications, it minimized the problems with pinholes, light millage areas, and solvent entrapment. The misconception has been that you can apply the total thickness requirement in one coat with multiple passes. The thicker film does not alleviate some of the problems associated with one coat.

Wet Sandblasting
The incorporation of water into the sandblasting operation in order to minimize dust.

Wetting
The ability of a vehicle to flow onto the surface in order to achieve a good bond.

White Rust
The oxide of zinc formed on galvanized metal.