5.1 The porosity of a paint film is closely related to the important practical characteristics of stain resistance, abrasion resistance, durability, and the hold-out of any paint subsequently applied.

5.2 This test provides a precise means for evaluating and comparing the quality of paint films, insofar as it pertains to porosity as determined on a coating applied to a nonporous substrate. Porosity measured using this test method may not be an accurate predictor of coating porosity when the coating is applied to substrate of higher absorption characteristics.

5.3 Unlike current Test Method D3258 Porosity of Paint Films, which is effective only with light-colored paints, this test method is equally effective with paints of any color, both dark and light. Also unlike Test Method D3258, its results are not influenced by the hiding characteristics of the paint film.

1.1 This test method is applicable to air-dry architectural coatings of any type, both solvent and water-borne, and of any color, dark as well as light. It cannot be used with films that are dissolved or excessively softened by mineral oil, but practical examples of such films will be encountered rarely, if ever.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.