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D344-11 – Standard Test Method Technical Guide
🧪 Scope and Significance of D344
ASTM D344-11 (Reapproved 2016), originally approved in 1932, provides a standard test method for the visual determination of the hiding power of a test paint relative to a comparison paint. This method is performed by evaluating brushouts on black and white hiding power charts.
The standard establishes both a qualitative and a quantitative assessment. Qualitatively, a paint is characterized as better, equal, or poorer in hiding power. Quantitatively, the result is expressed as a percentage of the spreading rate of the comparison paint at equal hiding. The values stated in SI units are regarded as standard.
⚠️ Relative vs. Absolute: This method specifically measures relative hiding power. The results have significance only within the relationship between the test paint and the comparison paint. For absolute hiding power, refer to Test Method D2805 (Hiding Power of Paints by Reflectometry).
The hiding power of a paint, when applied by brush, is affected by the variations in film thickness inherent to the application method. Two paints that hide equally by this brushout method might behave differently when applied with a doctor blade, which enforces a more uniform film thickness.
⚙️ Test Procedure: Qualitative and Quantitative Brushouts
Qualitative Procedure: The test paint and the comparison paint are brushed out uniformly at the same spreading rate on black and white hiding power charts. After drying, the brushouts are evaluated visually to see which paint has been most effective in reducing the substrate contrast.
Quantitative Procedure: Additional brushouts of the comparison paint are made at varying spreading rates to determine the rate at which it visually matches the hiding of the original test paint brushout