ABSTRACT
In a bubble time viscometer, a liquid streams downward in the annular zone between the glass wall of a sealed tube and the perimeter of a rising air bubble. The capillary-tube viscometer consists of a fluid reservoir to hold a specified volume of sample liquid and of a capillary tube. Automatic capillary-tube viscometers are designed to operate using conventional glassware and to give precise kinematic viscosity measurements automatically. The capillary-tube viscometers are limited to the measurements of low-viscosity Newtonian fluids because of the small driving force and inability to vary the shear stress and shear rates. Efflux cup viscometers are most commonly used for fieldwork to measure the viscosity of oils, syrups, varnish, lacquer, paints, and bitumen emulsions, although they have some inherent inaccuracies. Ford cup viscometers are used for the determination of low viscosity liquids that do not deviate much from the ideal liquid behavior. The rotational viscometer is probably the most widely used rheometer.
