Abstract background of colorful painted water and oil

High Viscosity

Originally contributed by Jeff Butler • last updated 2/22/2021

When you think about the thickness of honey compared to water, you can probably start to imagine how much slower it flows, as if its layers were working against each other to retain their shape. In much the same way, you can probably imagine how thin water is and how fast it can flow when it’s pouring out of a faucet. The thickness of a liquid, like honey or water, is typically measured in terms of its viscosity, with honey being highly viscous compared to water.

Definition

Technically, the term viscosity refers to a liquid’s resistance to flow or deformation — in essence, its resistance to change. More generally, the terms high and low viscosity can be thought of as the thickness or thinness of a liquid. Typically, the thicker a liquid is, the more viscous it is and the thinner a liquid is, the less viscous it is. Conceptually, viscosity can be thought of as the result of the friction between the layers of a liquid as it moves, with thicker liquids moving slower and thinner liquids moving faster.

When Does The Term Viscosity Get Used?

When dealing with certain liquids, it’s important to understand how thick or thin they are and how that will impact your project. While it’s fairly easy to understand how thick or thin a liquid is, describing it sometimes requires a special vocabulary. Viscosity isn’t a word that gets used often but there are times when knowing how to use it could come in very handy. For example:

  • The viscosity of paints and finishes may determine how easily they can be applied with different tools, such as brushes, rollers, and sprayers. If a paint or finish is highly viscous, it will generally be harder to spread over a surface. How thick a paint is can also determine how the surface will appear when it’s dry.
  • Viscosity is also a word that gets used to describe the thickness of engine oils for equipment, like lawn mowers and snow blowers. Oils that are less viscous typically reduce the amount of friction in an engine, allowing parts to move easier, especially in colder weather.
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