The capillary method is one of the oldest methods used to determine the surface tension in liquids or gases.
Capillary rise takes place due to the cohesive and the adhesive forces that force the liquid to rise in the tube through a very small diameter.
Capillary action in soldering:
Capillary action is based on the principle of surface tension.
Capillary action allows the deposition of molten substances like any alloy, metal, etc. in between the two metal surfaces.
In the soldering process, the molten solder rises due to the capillary force into the cracks in between the parts that are to be joined. It allows the permanent joining of two metal pieces.