viscosity (asphalt) - determined by any of several ASTM test methods. Two common methods are ASTM D 2170 and D 2171. The former method measures kinematic viscosity, that is, viscosity under the force of gravity, by allowing a test sample to flow down a capillary tube (viscometer) at a temperature of 135°C (275°F); the viscosity is expressed in centistokes. The latter method measures absolute viscosity. The liquid, at a temperature of 60 °C (140°F), is drawn up a tube by applying a vacuum; the viscosity is expressed in poises. In both tests the viscosity is obtained by multiplying the flow time in seconds by the viscometer calibration factor. See penetration (asphalt), viscosity.