In this method, a sphere of known density is dropped into a fluid sample, and the user records the time it takes for the sphere to fall to a specified point. The Zahn cup is still frequently used in the paint industry. The time it takes to empty the cup of the liquid, through the hole, forms the basis of the measurement of viscosity. This is a small container with a handle and a small hole in the bottom. These devices are still in use and are called Ostwald or Ubbelohde Viscometers. This traditional way of measuring viscosity used capillary tubes to measure the time it took for a volume of liquid to traverse the length of the tube. Here are a few different techniques used today.
In the 1800’s, the earliest measurements of viscosity were taken with capillary tubes. The most popular measurement tool is called a Viscometer (several types exist).
Instruments vary from simple, like counting the seconds for a liquid to drain off a device, to sophisticated automatic recording and controlling equipment. There are different techniques for measuring viscosity, each suited to particular materials and conditions. Data on a material’s viscosity gives manufacturers valuable knowledge of its characteristics to help predict pumpability and pourability, performance in specific operations, and ease of handling.
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