Standard Bench Viscometry Methods for Aqueous Paper Coating Emulsions
Bench viscometry of paper coating emulsions requires standardized temperature control, verified spindle geometry, and multi-shear profiling to ensure runnability.
Brookfield Viscometry
Rotational Measurement Method
A measurement technique determines the resistance of a fluid to a sensing element turning at a known speed. Manufacturers use brookfield viscometry to establish the low-shear behavior of paper coating colors before they reach the application head. The method defines the base flow properties required for pumping and mixing within the kitchen.
Low Shear Characterization
Calibrated springs and spindles interact with the sample to produce a reading based on fluid drag. Operators select specific spindle geometries to match the expected thickness of the liquid. High-viscosity fluids require smaller spindles or slower speeds to avoid overloading the sensor.
Temperature control remains a requirement because even slight shifts alter the recorded centipoise value.
Coating Formulation Application
Stability in the coating kitchen depends on consistent readings across different batches. A brookfield viscometry reading provides a reliable benchmark for storage stability without accounting for the extreme forces at the blade tip. Discrepancies here indicate problems with pigment dispersion or binder shock during the blending stage.
Correcting these issues prevents poor leveling on the base sheet. Regular logging of these values helps a mill maintain a historical record of formulation performance under different environmental conditions. Adjustments to the recipe often follow a shift in these results to maintain a steady flow through the supply lines.