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σ：Surface Tension△P：Pressure Diff erencer：Capillary Diameter13（plate method or vertical plate method）When a plate touches a liquid surface, the liquid moves up and wets the plate, and the surface tension acts along the plate’s perimeter as a force pulling the plate into the liquid. To determine the surface tension, the magnitude of this force is measured.By reason of intermolecular forces, surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible.⇒ This tendency is referred to as interfacial tension, and especially as surface tension at a liquid-air interface.Surface tension that becomes equilibrated over time is referred to as “dynamic surface tension”, while surface tension that is in equilibrium is referred to as “static surface tension”.⇒ Generally, dynamic surface tension tends to be higher than static surface tension and it is harder to wet a material in contact with a liquid.Diff erent from "Static Surface Tension" obtained by measuring the surface tension of a static interface, the dynamic surface tension represents surface tension of an interface in motion.Liquid is fl owing due to agitation, circulation, application, etc. in many cases when "wetting" is actually considered; therefore, the dynamic surface tension is a more practical index of "wetting."A contact angle represents how easily liquid is wet to a solid surface. A surface that is easy to wet (liquid that easily wets a surface) has a low contact angle, and a surface that is hard to wet (liquid that has diffi culty wetting a surface) has a high contact angle.◯Surface tension (static/dynamic)◯Dynamic Surface Tension◯Contact Angle◯ Static surface tension Wilhelmy methodσ= △P・r2Explanation of TerminologyGlossary, Measuring method