Shear Stress - Shear Rate

Viscosity! If you ever think about it, what do you see?

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Topics: Newtonian Fluid, Viscometers, Dynamic Viscosity, viscometer, rotational viscometer, Viscosity Stress, Viscosity Shear Rate, Non Newtonian

At first glance, viscosity seems like a fairly simple concept. It helps describe how thick a product is, or how well it flows. That's all, right?

In reality, there are several different terms that come under the heading of viscosity. These terms are derived from how the viscosity is measured. When people talk about viscosity, they are talking about one of two things: kinematic viscosity or dynamic viscosity.

It's not easy to find a lot of information on the differences between dynamic and kinematic viscosity. This is my attempt to bring clarity to these two principal concepts.

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Topics: Newtonian Fluid, Viscometers, Viscosity, Consistency, Kinematic Viscosity, Dynamic Viscosity, rotational viscometer, Liquid Properties, density, Texture Analysis, gel time

Looking at the rotational viscometers on the market today, you'd expect to see small price differences between the instruments offered by competing brands. But what if you find one viscometer priced at $2000 and another at $9000? Is the $9000 viscometer a better instrument? Why is there such a price difference between the two instruments? 

Viscometer prices depend on both the make-up of the instrument's motor, and on the technical features of the instrument (temperature probe, speed range, USB compatibility, etc.). There are two main types of rotational viscometers: those using a spring motor, and those using a servo motor. 

In this article, I’m going to take a look the options available for rotational viscometers, and how those options affect the price.

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Topics: Viscometers, Viscosity, Dynamic Viscosity, rotational viscometer, Liquid Properties

Most rotational viscometer specifications promise high test accuracy and repeatability. However, an instrument on its own cannot guarantee accurate results. Instrument set-up and using the right test parameters are critical pieces of the puzzle. 

Test parameters and turbulence are two key factors to consider when preparing to test with a rotational viscometer. The spindle, speed setting, and temperature of the product are some of the parameters that can impact test results. Additionally, turbulence in the sample’s flow during a test will distort viscosity readings. Knowing how to manage these two factors can significantly contribute to the accuracy of your testing.

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Topics: Measure Viscosity, Viscometers, Viscosity, Dynamic Viscosity, rotational viscometer, Liquid Properties