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, it is not always crucial to evaluate bead formation with this level of precision. A proposed ASTM International standard that will provide a visual rating guideline on the degree of water beading can be used without the need for precise imaging equipment.
ASTM 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. ASTM WK32143 will provide formulators with a means for evaluating the water beading capability of a coating. Repeating the test described in ASTM WK32143 after coated specimens have been put through intervals of ageing or weathering will demonstrate the persistence of the coating’s ability to bead water.
Although 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.