Viscosity Units of Measure: What does INDCO Need to Help Me?

Frequent INDCO customers know that we always ask for liquid material properties in order to make the best possible mixing equipment recommendations.  Viscosity is usually our first request.  As simple as that sounds it gets a little bit more involved upon the realization that viscosity is expressed in a number of different units.

The poise, named for the French physician Jean Louis Marie Poiseuille, is the viscosity of fluid in which a tangent force of 1 dyne-second per square centimeter maintains a change in velocity of 1 centimeter per second between parallel lines one centimeter apart.  The centipoise, or 1/100 of one poise is a very common measure and the one we work with most frequently.   The viscosity of water is 1 centipoise and many common liquids are between 1 and 1,000.  Other common measures include stokes and centistokes.  One centistoke is the viscosity in poise divided by the density of the fluid.  Therefore, conversion between these two measures is relatively simple.

Other viscosity measures involve the measurement of time.  For example, Saybolt Seconds Universal is the time that it takes for a specific volume of fluid to flow through a calibrated orifice of a Saybolt Universal viscometer.  A similar but less precise method involves the measurement of the time it takes a liquid to drain from a cup with a standard hole diameter in the bottom.  This method utilizing the Zahn cup is common in the paint industry.

There are many conversion tools and charts available online.  A quick search for “viscosity measurement conversions” or “viscosity units of measure” should yield ample reading material on the subject.  As always, you can call your INDCO applications engineer to assist you!