Inadequate thickness may lead to premature failure in salt spray or UV exposure tests.
ASTM D823 describes four distinct practices for preparing uniform films of paints, varnishes, and other coating materials on flat test panels. The primary purpose is to ensure that laboratory-prepared coated panels have a consistent, controlled film thickness for subsequent tests (e.g., color, gloss, hiding power, or mechanical properties). Unlike drawdown bars (ASTM D823) that create a wet film of fixed clearance, these practices use precision applicators to control thickness via blade gap or applicator weight. astm d823
For a given wet-film applicator gap (G) and coating’s volume solids (VS% as a decimal), the theoretical dry film thickness (DFT) is: Inadequate thickness may lead to premature failure in
For products that are typically coated by dipping, Practice B uses a motor-driven device to withdraw a test panel from a container of liquid coating at a constant, controlled speed. The withdrawal rate is the primary factor determining the final film thickness. Unlike drawdown bars (ASTM D823) that create a
This method is favored for its simplicity and the ability to produce very thin, precise layers of inks, resins, or food-grade coatings. Practice D: Manual Hand Blade Application