How to Use a Paint Thickness Gauge (And Why It's Important)

How to Use a Paint Thickness Gauge Author - Andy Potts July 6th 2020 (reading time 2 mins)

paint thickness measurement

Example of a Wet Film Paint Thickness Gauge

High-performance coating manufacturers always recommend target thickness ranges on their product technical datasheets. Adhering to these specifications is critical to ensure that the product achieves optimum performance characteristics. Your clients rely on you to meet these requirements, so it's essential to test film thickness at every stage of the application process. This article explains the different testing methods, when you would use them and which paint thickness gauge to use.

Why is paint thickness measurement so important?

The client's perspective

Your clients select high-performance coatings for their products because they offer specific properties, such as:

Resistance to water, corrosion or fire
Aesthetics
Adhesion to difficult surfaces

If you don't apply the coating in line with target thickness ranges, your clients' products will not live up to their claims. Imagine you were finishing a product in intumescent fire paint that offers 60 minutes of fire protection, for example. If your film thickness is below the manufacturer's recommended range, the product won't offer that level of protection. Overcoating can cause just as many problems as undercoating.

Benefits for your spray shop

It's obviously in your interests to meet contract specifications. But, using a paint thickness tester also helps you to:

Control material costs
Manage application efficiency
Maintain top-quality finishes

How to check paint thickness

There are two methods for testing film thickness - wet film thickness (WFT) measurement and dry film thickness (DFT) measurement.

Wet film thickness measurement

As the name suggests, the painter performs this test during the application, when the paint is still wet. Measuring every coat allows you to adjust the thickness to meet the manufacturer's recommendations.

Use the wet film thickness measurement to predict the dry film thickness once the coating has cured. You can do this easily using the wet and dry film thickness formula.

Wet film thickness gauges

A wet film gauge, also known as wet film thickness comb, is the best tool for this type of film measurement. You can either buy a selection of combs with different scales to match different film thickness needs or a single gauge with a wide range and high resolution of measurement to cater for all types of application. All combs work in the same way.

How do you use a wet film paint thickness gauge?

The technology is cheap and simple to use. After applying a coat to the substrate, test the thickness in an area that's out of sight.

STEP 1:	Using the edge of the comb with the smallest set of micron thicknesses, press the comb down evenly, at a 90ø angle to the paintwork. The outside teeth will press against the substrate and paint will mark the graduated teeth of the comb.
STEP 2:	Remove the comb, turn it, and take a second measurement using the next set of micron thicknesses. Your WFT is the highest number tooth on the comb that is marked with paint.
STEP 3:	Check the film thickness against the WFT requirements on the manufacturer's technical data sheet to establish how many more applications are required to achieve the correct wet film thickness.
STEP 4:	Either let the comb dry and keep it as a record of the WFT or clean it with solvents for reuse.
STEP 5:	Repeat this process for each coat.

Dry film thickness measurement

The spray shop supervisor or inspector generally has the job of DFT testing. They often measure coating thickness at various stages of the project to check that each coat is up to standard and suitable to over-paint. A final check at the end of the project confirms that all areas of the coating meet specification requirements.

Dry film thickness gauges

DFT testing technology is more advanced, and therefore more expensive than WFT testing. DFT gauges generally use magnetic induction probes that use eddy current principles to measure the depth of coating. There is a range of monitors on the market. Some have standard functionality and others can store a large amount of data that you can download to a PC for

checking and filing.

Learn more about DFT and WFT Gauges with our quick video guides


Wet Film Paint Thickness gauge Video	Dry Film Paint Thickness gauge Video

Buy WFT and DFT gauges at Ultrimax

We stock wet paint combs and a selection of DeFelsko gauges in our online shop. If you're not sure which model to buy, or need a hand with the testing process, contact our Total Paint Shop Support Team who will be more than happy to help.