ASTM Testing to Measure Washability Properties of Wall Paints

    Last month we outlined the performance parameters required for the testing of Scrub Resistance of waterborne architectural coatings. This month we will discuss a related test, washability.

    While scrub resistance is the ability of a paint surface to resist wear when rubbed with a brush, sponge or cloth, washability is the ability to remove stains from the surface with little wear. This is important for frequently soiled surfaces such as doorways since easy removal with little wear ensures the paint remains intact. A typical standard such as ASTM D3450 – 15 “Standard Test Method for Washability Properties of Interior Architectural Coatings” is often used. Individual laboratories such as 1st Source Research also provide custom tests to better mimic the conditions of use.

    Standard vinyl acrylic based paints perform well for hydrophobic stain removal such as lipstick. More hydrophobic latexes produce better wash-off capabilities for hydrophilic stains such as coffee and wine. 100% acrylic latexes provide a balance of properties for both hydrophilic and hydrophobic stain removal. Proprietary additives are often used to enhance certain stain removal properties. Note that it can be beneficial to perform the stain removal test twice in the same area. This is to ensure that simple additives that resist stains are not washed off during the initial test, thus providing little or no benefit for the removal of subsequent stains.

    At 1st Source, we routinely test paints for improved washability or stain removal. Testing requires appropriate controls and coating thickness. The use of a constant temperature/constant humidity room ensures consistent drying conditions for all tests. Appropriate substrates and cleaning materials are important. Enhanced testing equipment such as scanning electron microscopy (SEM) and its related instrumentation energy-dispersive x-ray spectroscopy (EDX) significantly add to our capability to diagnose problems and provide solutions.

    1st Source has a strong coatings team that allows us to combines these techniques with other sophisticated analytical tools to diagnose paint quality problems, validate raw materials, and optimize processes that may be holding you back. Feel free to contact us. We will be happy to lend our expertise and analysis techniques to help you meet your goals.