hese tools can apply either a constant or a continuously variable wet film wedge from 0 to approximately half of the maximum blade depth
from Paul N. Gardner Co., Inc.
(U.S. Patent #4,869,200)
This applicator design offers one of the most accurate and reproducible ways to apply coatings to flat surfaces. Since most coating properties are thickness-dependent, it is imperative that an optimum thickness be determined for each application. The continuous thickness gradient produced by these tools is ideal for hiding power evalution; it can also be used to test coating flexibility, tack strength, spreading rate, fineness of grind, and other coating attributes.
With both side plates adjusted to the same depth, a uniform coating is produced; to create a wedge-shaped swath, set one end plate to double the maximum wet film thickness desired, while the other plate is similarly set to double the minimum thickness desired (like all blade type applicators, the ratio of blade clearance to wet film thickness may vary somewhat, being affected by drawdown rate, as well as coating rheology and surface tension – on the average, the ratio is about 2:1)