AA-GWR Water Retention Meter 250
The digital model 250’s cell pressure is set using a pressure reference knob and an LCD display. This model utilizes a servo pressure control system, which is comprised of two valves, a pressure sensor, and electronic control circuitry. Pressure in the measuring cell is continuously monitored and, if necessary, adjusted to maintain precise control to within ±1% of full scale.
The absorbing paper is weighed and placed on the lower mat. The filter and cup are set on top of the paper. The system is sealed by the magnets on the cup and lower mat. The coating is then poured into the test cell and placed into the unit. The test cell is then pressurized for a given time period. Upon completion of the test period, the paper is re-weighed to determine the amount of liquid de-watered from the coating.
The method is based on pressure filtration of coatings under externally applied air pressure over a certain time period. It utilizes gravimetric determination of the aqueous phase penetrating through a filter and absorbed by a paper sample. The measurement is very sensitive to changes in coating color formulation and has good reproducibility because the procedure is simple and the measurement system is well-defined. Various contact times and pressures can be easily studied.