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.

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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.

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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.

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Official TAPPI Test Method 

AA-GWR Model 250 Manual