A Ford viscometer or Ford viscosity flow cup uses gravity to measure the flow rate of a liquid. Under ideal conditions, flow rate is proportional to kinematic viscosity. Thus, a Ford cup is used to determine the kinematic viscosity of fluids. However, Ford viscosity cups should only be used with low-viscosity fluids. High-viscosity liquids and thick pastes are not suitable for measurement by means of a Ford cup. The structure of a Ford flow cup is standardized according to ASTM D1200 (Ford).

Basic operation
Cover the holes at the bottom of the orifice and pour in the liquid to be measured. Make sure that the viscosity flow cup is completely filled. Use the glass plate to scrape off any excess liquid from the edge of the flow cup. Uncover the holes at the bottom of the orifice. Negative pressure will keep the liquid in the cup until you're ready to begin measuring. Active a stopwatch (not included) while simultaneously removing the glass plate from the cup horizontally. As soon as the flow is interrupted for the first time, stop the watch and write down the time.

Note: When using a viscosity flow cup, it is very important to make sure that the instrument is cleaned thoroughly after each measurement, as residue in the orifice and cup can jeopardize the accuracy of future measurements. Scratches also can cause inaccurate results.