Methods of foam testing
When developing new products it is essential to exactly differentiate properties. Thus, the foaming behaviour of liquids has to be tested particularly with regard to the application. This is done in two steps. First, foam has to be produced and second, the foam height has to be measured.
Conventional methods of generating foam are based on mechanical principals such as agitation (ASTM D3601-88 (Re-approved 1997)), beating (DIN 53902-1), Ross-Miles Method (DIN 53902-2), shower (DIN 51395-1) or insertion of air.
The following methods are used to measure the height of the foam:
Visual
By means of a vessel with a measuring scale, the foam height is visually determined by the user in specific intervals. This demands great care because the foam surface is not even and consequently, subjective mistakes are not eliminated.
Trancparency
The foam height is measured with a light source and a light sensor. The foam refracts the emitted light and hence, shades the light sensor. The measuring result can be falsified due to contamination of the vessel. Unevenness of the foam height is not recorded.
In using these methods of testing foam there is the disadvantage that either the measuring results are not reproducible or subjective influences effect the results.
The SITA FoamTester uses innovative optical measuring methods to determine foam characteristics such as foam volume, stability, drainage as well as foam structure.