Measurement of foam drainage

After foam formation the liquid starts to drain out of the foam. The excess liquid in the foam film drains into the plateau borders, then through them, flowing down 

Simultaneously with drainage from films into borders the Uquid begins to flow out from the foam, when the pressure in the lower foam Aims outweighs the external pressure. This process is similar to gel syneresis and it is sometimes referred to as foam syneresis and foam drainage . 

The rate of foam drainage is determined by the hydrodynamic characteristics of the foam as well as the rate of internal foam collapse and breakdown of the foam column. The foam drainage is determined by measuring the quantity of liquid that drains from the foam per unit time. Various types of vessels and graduated tubes can be used to measure the liquid quantity draining from a foam. Alternatively, one can measure the change in electrical conductivity of the layer at the vessel mouth compared with the electrical conductivity of the foaming solution [4). 

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