Coatings are everywhere around us. From the carefully painted walls in our homes to the sleek finishes on our cars, coatings play a vital role in protecting and beautifying various surfaces. One essential property that dictates how coatings behave and appear is viscosity. Here we will dive into viscosity and explore its importance in understanding the flow of coatings.

What is Viscosity?

Viscosity refers to the resistance of a liquid to flow. It is a fundamental property that determines how easily a substance can be poured, spread, or manipulated. In the realm of coatings, understanding viscosity is crucial for achieving consistent application, desirable surface finishes, and optimal performance.

Consistency: The Key to Success

Consistency is key when it comes to applying coatings. Imagine trying to paint a wall with a coating that is like peanut butter—it would be difficult to spread evenly, resulting in an uneven and unattractive finish. Similarly, a coating that is like drinking soda may not provide adequate coverage and protection. Maintaining a material’s viscosity ensures that coatings have the right consistency for smooth and uniform application. In some instances, people in the coatings industry refer to a material with a high viscosity value as ‘thick’ and a material with a low viscosity value as ‘thin’. This should not be confused by the thickness (build) of the coating.

Brushing and Spraying: Finding the Balance

Different application methods require different viscosity levels. When brushing a coating onto a surface, it is essential to have a viscosity that allows for easy application without excessive dripping or running. Coatings with higher viscosity are typically used in brush applications to achieve better control. On the other hand, when using a spray gun, a lower viscosity is necessary for even distribution and fine atomization. Finding the right viscosity for each application method is crucial for achieving the desired results.

Air Release

One reason that a material’s viscosity needs to be low during spray application is to accommodate the atomization of the material; however, another reason is that, because a great deal of air gets introduced into the coating, the lower viscosity material allows air to come to the surface and be eliminated from the coating prior to the material solidifying (setting) more easily. Don’t let the air be forgotten with brush and roller applied materials. Air gets introduced into any application process. The key is to maintain a low enough viscosity prior to the coating reaching the solidification point to allow the air to be eradicated from the coating’s film. This is why all application techniques should be performed quickly and not ‘touched up’ after application and before drying.

Leveling: The Magic of Self-Smoothing Coatings

Ever wondered how coatings can achieve a flawless, smooth surface with no visible brush or roller marks? It’s all thanks to leveling. Leveling refers to the ability of a coating to flow and self-smooth, resulting in an even appearance. Proper viscosity ensures that coatings can level effectively, minimizing imperfections and creating a professional finish that enhances the visual appeal of the coated surface.

The Temperature Factor: Heat and Viscosity Control

Temperature plays a significant role in viscosity control. As coating materials are heated, their viscosity tends to decrease. Lower viscosity coatings flow more easily and exhibit improved leveling properties. By carefully controlling the temperature during the coating application, professionals can ensure optimal flow, coverage, and leveling. However, it is important to follow the manufacturer’s recommendations and avoid exceeding temperature limits, as this can affect both viscosity and coating performance.

Film Thickness Control: Getting it Right

Film thickness is a critical aspect of the coating process. Coatings with higher viscosities tend to create thicker film builds, while lower viscosity coatings may result in thinner film builds. Accurate viscosity control is essential for achieving the desired film thickness, ensuring optimal performance and durability. By measuring and adjusting viscosity throughout the application process, professionals can maintain the desired thickness (build) and deliver coatings that meet performance requirements.


Viscosity is a vital parameter in understanding the flow of coatings. From ensuring consistent application and precise control, to achieving smooth finishes and optimal performance, viscosity affects every aspect of the coating process. By understanding how viscosity influences consistency, brushing and spraying, release of air, leveling, temperature control, and film thickness, professionals can achieve remarkable results in coating application. So, the next time you paint a wall or apply a protective coating, remember the role of viscosity and unlock the key to a flawless finish!