Meaning and use

5.1 Due to poor compatibility, the colorant is sometimes not fully dispersed in the base paint, which may be a disadvantage of the colorant, the paint or both. This will result in poor color rendering, which is easily demonstrated by the conventional method of applying paint with a scraper and rubbing small areas of partially dried film through your fingers so that scraping produces high shear stress. This tends to disperse the undeveloped colorant (if any) and create a color change between the uncut and cut areas of the paint film. The change can be measured by comparison to give a numerical color difference value, which is a measure of the color development of the original paint, the smaller the difference, the better the color rendering, and vice versa. It is found that the color difference obtained by finger friction varies greatly for the same and different operators. This test method establishes a controlled shear stress procedure similar to a finger wipe test, but with better reproducibility.

5.2 Poor color development may be a problem in paint production, or it may be a problem in oilfield production. In production, it can lead to a loss of the monetary value of the colorant, as well as unpredictable coloring results. In field performance, changes in the color of the applied film result from varying shear forces that the paint is subjected to at different stages or through different modes of application.

ASTM D5326-0 “Standard Test Method for Color Development in Colored Latex Paints”

5.3 While poor color rendering is primarily and usually associated with the colorant portion of tinted coatings, white pigments in base coatings can also be poor due to flocculation or other reasons. In the latter case, shear dispersion can make the paint film lighter and less colorful, rather than the other way around. Then, the colorant and white may also both be poor, and the color change caused by shear stress will be a combined effect of both.

5.4 In any case, color rendering is an important coating property, and for measurement, this test method is intended to provide a generally accepted and repeatable test method.

Step 1: Scope

1.1 This test method includes procedures for measuring color development in tinted latex paints with the aim of determining the efficiency of the colorant, the tint of the base paint and the likelihood of poor color uniformity of the painted film.

1.2 Values in inches to pounds shall be considered as standard values. The values given in parentheses are mathematical transformations of SI units and are for reference only and are not considered standard.

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