Meaning and Purpose
5.1 The contrast at the specified film thickness is a useful hiding power parameter for production control and procurement specifications.

5.2 The greater the hiding power, the less paint is required per unit area to obtain sufficient hiding power. Therefore, knowledge of hiding power is important for coating costs and comparing coating values.

ASTM D 6441-1999 Standard Test Method for Determining the Hiding Power of Powder Coatings

Scope of
1.1 These test methods determine and report the hiding power of powder coatings based on two parameters:

1.1.1 Test Method A — Contrast at a given film thickness

1.1.2 Test Method B — Film thickness at 0.98 (98%) contrast.

Note 1: The measurement parameters follow powder coating industry practice by measuring the hiding power with respect to film thickness, rather than the “spread rate” function used in test methods D344 and D2805 and other hiding power test methods.

Note 2: Hiding power is defined in luminosity as spread rate at 0.98 contrast. Please refer to terms D16, D2805 and the definitions of diffusivity and hiding power in the Paints and Coatings Testing Manual.

Note 3: A contrast ratio of 0.98 is generally accepted by the paint industry as “full” coverage for reflective coverage measurements. But visually and photologically, it is still slightly incomplete.

ASTM D 6441-1999 Standard Test Method for Determining the Hiding Power of Powder Coatings

1.2 These test methods include determination of the hiding power of electrostatic sprayed powder coatings.

1.3 These test methods determine the hiding power by measuring with reflectometer and thickness gauge. They are restricted to coatings with a minimum CIE-Y reflectivity of 15%.

1.4 Values expressed in SI units should be considered standard. The values given in parentheses are for reference only.

1.5 This standard is not intended to address all safety issues, if any, associated with its use. It is the responsibility of users of this standard to establish appropriate safety and health practices and to pre-determine the applicability of regulatory restrictions prior to use.