How to use the "Wet Film Thickness" meter

The Wet Film Thickness Gauge is designed to quickly and easily measure the thickness of a coating immediately after it has been applied to a substrate. These gauges are also commonly referred to as: Combs, MIL gauges, step gauges, and notch gauges. A gauge contains a series of notches cut into its sides, like the teeth on a comb. Can measure wet film thickness of most organic coatings including paints, resins, varnishes, varnishes, gel coats and more. The thickness of powder coatings can also be measured before curing.

"Wet Film Thickness Gauge" example

theory of operation

Teeth or notches machined into the side of the gauge. The teeth or notches on either side of the gauge are referenced to each other. For a given side, the two external teeth or notches are the same size and effectively represent a zero reference datum for the substrate. All other teeth or notches on the same side are shorter in length than the outer teeth or notches and represent different distances from the outer edge zero reference tooth. These different distances represent the thickness of the wet coating surface to be measured. Teeth or notches are graduated in MILS (0.001"). See diagram below.

Instructions on how to use the "Wet Film Thickness Gauge"

Place the wet Film Thickness Gauge at a ninety-degree angle to the coated substrate and penetrate the coating surface with the notch or toothed side of the gauge until firm contact is made with the substrate. Wait a few seconds for the teeth or notches of the gauge to be "wet" by the coating, then pull the gauge straight out so that it is at a 90-degree angle to the substrate. The gauge can now be read to determine wet film thickness. Visually inspect the end of the tooth or notch, some will be coated or "wet" and some will not. Coating wet film thickness (WFT) between the smallest uncoated (dry) tooth or notch and the largest coated (wet) tooth or notch. Always clean the meter with an appropriate solvent after use.

When wet film thickness is measured on a rough substrate, the thickness measurement will most likely be from a surface "peak" and the wet film thickness measurement will represent the minimum overall wet film thickness.

On curved surfaces such as pipes, cylinders, etc., gauges should be used along the length or longitudinal axis of the surface.

If you are measuring a fast-drying coating, perform the measurement quickly to avoid errors that may be caused by curing.

Measuring Powder Coatings

The thickness of dry powder coatings can also be measured with these types of gauges. The mode of operation is similar to measuring "wet" coatings. The teeth or notches of the gauge should "drag" through the coating at a 90 degree angle and the thickness of the powder will be between the value of the smallest tooth or notch and the largest tooth or notch to which the powder "sticks" between. No powder "sticks". The "drag" marks left by the teeth or notches on the surface of the substrate can also be checked to confirm the value read from the notches or teeth. The "drag" mark indicates that the tooth or notch should have the coating "attached" to it.