ASTM-D3258 Standard Test Method for Porosity of White or Near White Paint Films by Staining

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This test method details the standard procedure for determining the porosity of white or near white mineral spirits insoluble paint film by staining to indicate the degree to which a subsequent coat will penetrate. This test method shall require the use of film applicators, reflectometer, vacuum drawdown plate, camelhair brush, plastic wash bottle, test panel, penetrating medium, and filter paper. The test paint is applied to a nonporous surface, air dried, then measured for reflectance. A special colored penetrating medium is applied, the excess removed in a specified manner, and reflectance measured again. The difference between the two readings indicates the degree of porosity; the smaller the difference, the lower the porosity of the film and the greater its ability to resist penetration.




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1.1 This test method covers the determination of the porosity of a white or near white mineral spirits insoluble paint film to indicate the degree to which a subsequent coat will penetrate.

1.2 The texture of the film can affect cleanup that will influence the results of the test. A stain applied to a high-hiding paint will not lower the reflectance as much as the same stain applied to a low-hiding paint of equal porosity. These points must be considered in comparing different paints.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 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.

1.5 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.


film porosity; porosity; resistance—penetration (into paint films);; ICS Number Code 87.040 (Paints and varnishes)

To find similar documents by ASTM Volume:

06.02 (Paint -- Products and Applications; Protective Coatings; Pipeline Coatings)

To find similar documents by classification:

87.040 (Paints and varnishes Including coating powders, paint coatings and protective paint systems)

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Document Number


Revision Level

2004 R19 EDITION



Modification Type


Publication Date

April 1, 2019

Document Type

Test Method

Page Count

2 pages

Committee Number