Product Description Zahn cups can be used to quickly measure the viscosity of liquids such as paint, lacquer, varnish, syrup and oil Boekel cup type viscometers measure VIS Cosity in the 18 to 1725 centistokes range in 90 seconds or less. The viscosity Is measured by determining the amount of time it takes for a steady stream of sample to flow from the orifice in the bottom of the cup. This is cormaated to the viscosity in centistokes. measurements should be made at 77 F (25 C).