One of several configurations of cup designed to measure the viscosity of a fluid, in particular, a printing ink. Essentially, an efflux cup is a container with a hole at the bottom. The cup is lowered into the ink to be measured, then lifted out. When the hole is above the surface of the ink reservoir, a stopwatch is started, and the time it takes a fixed quantity to flow out of the hole can be measured. Efflux cups come in a variety of shapes and sizes, such as a Ford Cup, a Zahn Cup, a Shell Cup, and a GRI Hiccup. Each configuration of cup comes with a set of different hole sizes, suitable for inks with a range of viscosities. For example, a thicker, more viscous ink requires a larger hole than a thinner, less viscous ink. Several different readings should be taken for the same ink and averaged, as long as each reading is within ±0.5 second of each other. The measurement of an ink's viscosity is an important factor in many printing processes, in particular gravure and flexographic printing. (See also Viscosity.)
|