Goniometers: Uses in Surface Tension Measurement

When you need details on contamination, adhesion, surface energy, and printability of a surface, a goniometer could be just the test and measurement solution you need. These handy devices offer a non-destructive testing method that measures the contact angle of a droplet on a surface to determine a number of important material properties.  

What is a goniometer? 

Goniometers, also sometimes known as tensiometers, are tools designed to measure the surface tension of liquids such as coatings, adhesives and lacquers. They are also often referred to as contact angle goniometers, thanks to their additional application in determining the wettability of a surface using the angle of contact method. These are the two main functions of these handy measuring instruments.  

The working principle of a goniometer

A goniometer uses the contact angle method to take a quantitative measure of surface wettability.  

The three-phase boundary where a gas, a liquid and a solid intersect can be inspected to determine the angle formed. This gives a geometric definition to the wetting of a solid by a liquid and can be expressed by Young’s equation: 

γSV = γSl+ γlv cosθY  

This method also measures a solid-surface’s characteristic surface free energy (SFE) and surface tension. The surface tension of a liquid is the equivalent parameter to the SFE of a solid and the contact angle can be used to determine both. The probe liquid used in this testing can influence the results, so it’s essential to set the goniometer to record the materials used in testing. 

The ability to determine surface tension and the Young contact angle of a droplet can be important for many industrial applications, that’s why we have fast and accurate goniometers available at Industrial Physics.  

How to use a goniometer to measure surface tension

To use a goniometer to perform dynamic tests like measuring surface tension or the wettability of a surface, you first need to enter the parameters into the digital goniometer. This includes droplet size, method of deposit, start delay, and sample rate. The goniometer can then be placed directly on the sample surface and set to take a series of pictures using its inbuilt camera. Once the pictures have been taken, the goniometer’s software will analyze the contact angle and return the results. 

How to read a goniometer

The first contact angle goniometers were manually operated and used an eyepiece with a microscope. The user had to record measurements themselves. Modern contact angle goniometers use a camera to capture the drop shape and software to analyze its angle. This means the results are transferred to a PC, allowing the user to determine all important data quickly and easily.  

Goniometers and material testing

Goniometers testing is typically performed with deionized water, but other liquids can also be used, such as coatings, paints, or adhesives. Because goniometers can also be used to test the qualities of a surface, they are also suitable for testing on materials such as carboard, corrugated paper, steel, aluminum and more.   

Goniometers at Industrial Physics

When you need to quality test coatings and paints or the absorption properties of a surface, we have just the solutions for you, including: 

TQC Sheen Fibro PGX+ Pocket Goniometer

The Pocket Goniometer PGX+ is a portable and accurate testing tool perfect for defining several surface properties for quality control. It measures the dynamic and static contact angle of a standard liquid on a wide variety of surfaces, including paper and board, solar cell panels, windshields, metal cylinders and similar. 

Its camera can take up to 80 pictures a second, allowing for an accurate measurement of both the static and the dynamic contact angle of a droplet, as well as surface tension and surface free energy (SFE). Quick analysis is allowed through software that can be used on your PC. Find out more about the Fibro PGX+ Pocket Goniometer.  

Goniometers and international standards

Goniometers are available in several different forms and designed for a variety of applications. Some of the most relevant standards for in the Flexible Packaging and Inks and Coatings sectors include: 

• ASTM D724: Standard test for surface wettability of paper (angle of contact method) 

• TAPPI T458: Standard test for surface wettability of paper (angle of contact method) 
• ASTM D5946: Standard test for Corona treated polymer films using water contact angle measurements. 

When you choose testing solutions from Industrial Physics, you can be rest assured that they are designed and developed to meet standard testing requirements for the applicable testing industries.  

Surface testing with Industrial Physics

Our engineers have in-depth knowledge of their industries and our specialised brands, such as TQC Sheen, are at the forefront of their fields. When you need a test and measurement solution, whether it’s an adjustment to your existing set up or a quality control system build from the ground up, we’re here to help. Check out our Fibro PGX+ Pocket Goniometer or our full range of TQC Sheen products.