Coating Film Thickness Measurement Glossary and Fact Sheet

Multiply the wet film thickness by the coating’s volume solids percentage, divided by 100: DFT = WFT x (volume solids % / 100). For example, a 100 micron wet film of a 50 percent solids coating gives roughly 50 microns dry film. Check the coating supplier’s data sheet for exact volume solids.

Both measure wet film thickness. A comb gauge is quick, low-cost, and ideal for flat surfaces and spot checks. A wheel gauge rolls across the surface and suits wet lacquers, paints, and coil-coated surfaces where a rolling action gives a cleaner reading. Choose based on surface type and how many readings you take.

Both are non-destructive dry film methods. Magnetic induction measures non-magnetic coatings on ferrous substrates such as steel and iron. Eddy current measures non-conductive coatings on non-ferrous metals such as aluminum, copper, and brass. Many gauges combine both and detect the substrate automatically.

Yes. Non-metallic substrates need ultrasonic measurement rather than magnetic or eddy current methods. An ultrasonic gauge sends a pulse through the coating and measures the echo, giving non-destructive readings on wood, concrete, plastic, composites, and fiberglass, including multi-layer systems.