PAINT AND COATINGS LABORATORY

Paint and Coatings Viscosity Testing

Touchstone utilizes various methods to measure the viscosity of paints and other liquids. The following is a brief explanation of Brookfield Visocometry according to ASTM D2196 and measurements with a Ford Viscosity Cup via ASTM D1200.

Brookfield Viscometer

"Standard Test Method for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield) Viscometer ASTM D 2196
ASTM D2196 cover the determination of the apparent viscosity and the shear thinning and thixotropic properties of non-Newtonian materials in the shear rate range from 0.1 to 50 s-1.
Test Method A consists of determining the apparent viscosity of coatings and related materials by measuring the torque on a spindle rotating at a constant speed in the material.

Test Methods B and C consist of determining the shear thinning and thixotropic (time-dependent) rheological properties of the materials. The viscosities of these materials are determined at a series of prescribed speeds of a rotational-type viscometer. The agitation of the material immediately preceding the viscosity measurements is carefully controlled.

Test Method A is used for determining the apparent viscosity at a given rotational speed, although viscosities at two or more speeds better characterize a non-Newtonian material than does the single viscosity measurement.

With Test Methods B and C, the extent of shear thinning is indicated by the drop in viscosity with increasing viscometer speed. The degree of thixotropy is indicated by comparison of viscosities at increasing and decreasing viscometer speeds (Test Method B), viscosity recovery (Test Method B), or viscosities before and after high shear (combination of Test Methods B and C). The high-shear treatment in Test Method C approximates shearing during paint application. The viscosity behavior measured after high shear is indicative of the characteristics of the paint soon after application.

Ford Viscosity Cup – ASTM D1200

ASTM D1200 covers the determination of the viscosity of Newtonian or near-Newtonian paints, varnishes, lacquers, and related liquid materials with the Ford-type efflux viscosity cup. If the material is non-Newtonian, that is, shear-thinning or thixotropic, Test Method D 2196 should be used.
The Ford viscosity cup is filled level full with the liquid under test, and the time for the material to flow through one of the standard orifices is measured.
ASTM D1200 is useful for the determination of package and application viscosities of a number of paints and other coatings and in the thinning of these materials, but is limited to Newtonian or near Newtonian liquids.

Reference: ASTM D1200 Standard Test Method for Viscosity by Ford Viscosity Cup

Index of Paint and Coatings Laboratory

ASTM D 1200 ASTM D 1200