Wet film gauges give the inspector a quick, low cost method of checking the thickness of freshly applied coatings. It is important that a coating is applied to the correct thickness. Applying too much wet coating will not only waste time and money, but there is also a possibility of the coating cracking during the curing process. Too little coating and there is a chance that the substrate will not be sufficiently covered. 

To control process variables, it is often desirable to measure whilst the film is still wet. Wet film measurements are also useful for systems where the dry film thickness can only be measured destructively.