Water beading is an aesthetic effect sometimes highlighted as a product feature by architectural coatings manufacturers who produce water-repellent wood finishes and deck stains. While water beading on a coated surface can be quantified through the use of a microscopic imaging system (D7334, Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement), it is not always crucial to evaluate bead formation with this level of precision. A proposed new ASTM International standard will provide a visual rating guideline on the degree of water beading that can be used without the need for precise imaging equipment.
WK32143, Test Method for Visual Assessment of Water Beading on Horizontal Coatings, is being developed by Subcommittee D01.42 on Architectural Coatings, part of ASTM Committee D01 on Paint and Related Coatings, Materials and Applications.
Certain coatings additives, such as waxes and silicones, enable distinct water bead formation. WK32143 will provide formulators with a practical means for evaluating the water beading capability of a coating. Repeating the test described in WK32143 after coated specimens have been put through intervals of aging or weathering will demonstrate the persistence of the coating’s ability to bead water.
“The proposed standard will be helpful because it provides coating formulators with a simple and standard tool to compare and optimize water beading characteristics,” says Neal Rogers, group leader, new product development, coatings research and development, Cook Composites and Polymers, and a D01.42 member. Rogers notes that coating formulators will be the primary users of WK32143.
“The formulators are likely to represent manufacturers of architectural paints or paint additives,” says Rogers. “Although the proposed standard is being developed from an architectural coating point of view, rating of the visual effect of water beading could also be applied to any horizontal coating system.”
Participation in the standards development process is welcome in any of the task groups under the jurisdiction of D01.42.
“Specific to WK32143, it would be of interest to add the perspectives of those who manufacture additives to enhance water beading or water repellency characteristics of coatings,” says Rogers.
Technical Information: Neal Rogers, Cook Composites and Polymers, North Kansas City, Mo.
ASTM Staff: Jeffrey Adkins