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AA-GWR Water Retention Meters

Principle of Measurement

The method is based on pressure filtration of coatings under an 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 colour 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.

To learn more, please read the article, "Measuring the water retention of coating colors," written by Stefan E. Sandas, Pekka J. Salminen, and Dan E. Eklund for the Tappi Journal, Vol. 72, No. 12, December 1989 issue.

How the AA-GWR Works

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.

Features and Benefits

  • Measures coating de-watering under pressure.
  • Identifies differences on absorptive properties of paper samples.
  • Rapid measurements, 2-5 minutes per test.
  • Easy to operate and clean.
  • Very high accuracy and repeatability.
  • Portable, ideal for on-site troubleshooting and problem solving at the mill.
  • Digital timer controls test duration and alerts the operator when the test is complete.

Model 150 - Discontinued

The analog model 150 uses a precision regulator to manually adjust cell pressure. Pressure is displayed on a dial gage with an accuracy of ±2.5%.


Model 250

The digital model 250's cell pressure is set using a pressure reference knob and a 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.

Official TAPPI Test Method
AA-GWR Model 250 Manual

Instrument Specifications

Test Cell Area

Sample Volume

Cell Pressure

Input Pressure




Dimensions (H x W x D)

Recommended Blotter Paper

Recommended Filter
8.0 cm²

10 ml

0 - 30 psi (0 - 2 bar)

100 psi (7 bar)

115 Volt or 220 Volt

LCD Digital Display, 0 - 9990 Second Counter

18 lbs. net

10 x 10 x 7 inches

Chromatography 17, 57 x 57 mm
(Our P/N GWR430)

Polycarbonate 5.0 micron filter, 47 mm diameter (Our P/N GWR420)

Download AA-GWR Brochure

Kaltec Scientific, Inc.
22425 Heslip Drive
Novi, MI 48375 USA
(248)349-8100 Fax (248)34908909



© 2011 Kaltec Scientific, Inc.