It seems that viscocity measurement is once again a popular subject, as it should be considering the impact it can have on print quality and ink consumption. There are a number of measuring cups used today dependent on the application, although they are all known as efflux cups. All are metal cups that contain a given amount of ink or other solution and each has a hole at the bottom. The ink or coating is measured in seconds in regard to how long it will take to drain through the hole, which in turn gives a viscosity reading. Two types of cups are most popular in the flexo industry: the Zahn and the Shell cup. Both have a hole at the bottom but the shell cup has a 1-inch tube attached to the drain hole. Maintaining the size of the cup and holes are critical to achieving accurate measurements so keeping them clean is fundemental to this. Both cups are made in a variety of sizes but generally you should use one that measures between 20-40 seconds. The most common types used is the No. 2 Zahn and the No. 3 Shell cup although as mentioned in a previous answer the DIN No. 4 cup is also gaining in popularity with some printers.