How to Measure Wet Film Thickness using Elcometer Wet Film Wheels

The Elcometer 3230 Wet Film Wheel is a high precision, accurate and easy to use instrument which measures the wet film thickness of coatings.

A wet film wheel has two outer wheels which rest on the substrate, and a smaller central wheel which is eccentric relative to the outer wheels.

By rolling the gauge through a wet coating, the central wheel eventually touches the film. This point on the scale indicates the thickness.

In addition to the standard wheels, Elcometer also offers a number of wet film wheels specifically designed for in line wet film measurements. This Elcometer 3230 Coil Coating Wet Film Wheels are designed for use in the coil coating process. The outer wheels are knurled to allow measurements to be taken on slippery coatings or on fast moving substrates.

Why measure wet film thickness

Wet film thickness measurement is an excellent quality control measure, which is easy to carry out and analyse. Wet film thickness measurement provides instant feedback on the quality of the film applied and allows corrections to be made while the application is proceeding.

By measuring the wet film thickness, it is possible to predict the dry film thickness. The dry film thickness can be calculated using the ‘solids to liquids’ ratio, also known as the volume solids content. For example: if the paint has a volume solids value of 80% and the wet film thickness is 200 µm, the dry film thickness will be 160 µm (200 µm x 80% = 160 µm).

How to measure wet film thickness using a wet film wheel

Hold the wheel by its central spindle, using either a finger and thumb or a wet film wheel handle. When placing the wheel into a wet film, it should be placed down evenly, with the maximum scale reading positioned closest to the substrate.

Gently roll the wheel along the coated substrate, either through half a rotation (180 degrees), or one complete rotation (360 degrees), depending on the standard being used, and remove from the surface.

When the central wheel reaches the thickness of the coating, it touches the paint and is “coated”. To determine the wet film thickness, locate the first point of contact of the paint on the central wheel, which is closest to the wheel’s maximum value, and read the thickness from the scale on the outside of the wheel.

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