Surface Tension & Capillary Action (Wetness)
Definition: Measures the amount of surface tension or wetness; Surface tension allows insects (e.g. water striders), usually denser than water, to float and stride on a water surface.
Ideal range: The surface tension determines the behavior of liquids in a number of processes and phenomena.
Wetting and wettability. The wetting of a solid by a liquid depends, among other things, on the surface tension. This plays a major role in washing and cleaning, and also in wetting processes such as printing and coating.
Droplet size: With a spray or an emulsion, the total surface area of the droplets is larger the smaller the individual droplets get. The size of droplets produced therefore depends on the surface tension.
Dispersions and dispersibility: Boundary surfaces are formed between solid particles and the liquid during dispersion. A high surface tension has a negative effect on the dispersibility, as contact between similar particles is preferred (formation of clots).
Method of measurement: There are number of ways to measure surface tension including Capillary rise method, Stallagmometer method – drop weight method, Wilhelmy plate or ring method and the Maximum bulk pressure method.
Method of Control: The surface tension can be manipulated by ionization (lowers the surface tension), the addition of surfactants (soap) or a ‘wetting agent’ e.g. sulfuric acid.
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