Wet film thickness is the thickness of the film of wet paint or any liquid coating. Wet thickness peaks immediately after application. It decreases once the volatiles and solvents in the envelope evaporate.
Measuring the wet film thickness of a paint or coating applied to a material is extremely beneficial in determining the proper thickness of a dry coating. Almost all protective coatings with higher performance should meet specific requirements for dry film thickness. Therefore, there is a direct relationship between wet film and dry film thickness.
The ratio of dry film to wet film is identified by the volume of volatiles present in the applied coating and the allowable thinning. In flat coatings, the wet film thickness is usually lower than the dry film thickness. Wet film thickness measurement at the point of application is good because it allows film adjustments and corrections to be made at the point of application. Once the film is chemically cured or dried, making corrections is time and labor intensive and can lead to film fouling. In addition, it can lead to problems such as decreased integrity and adhesion of the coating.
For measuring wet film thickness, various gauges are used. Common ones are:
Notched Gauge - For uneven surfaces such as rough concrete blocks. They are also a sanity choice in the field and workshop, especially for identifying estimated wet film thickness of commercial items whose shape and size are not suitable for other specification types (such as thin edge, oval, etc.).
Pfund and Interchemical Gages - Compared to notch gauges, these gauges are suitable for uniform surfaces and provide sensitive and accurate wet film thickness measurements.
