Term: wet film thickness (wft)

Wet Film Thickness (WFT) refers to the thickness of a coating (such as paint, primer, or sealant) immediately after it has been applied and before it has dried or cured. It is typically measured in microns (µm) or mils (1 mil = 0.001 inch).

Why WFT is important:

• Ensures the correct amount of product is applied to achieve the desired dry film thickness (DFT).
• Affects the coating’s performance, durability, and appearance.
• Helps avoid issues like sagging, poor coverage, or insufficient protection.

How WFT is measured:

• Using a wet film thickness gauge (also called a comb gauge or wheel gauge).
• The gauge is pressed into the wet coating, and the reading is taken from the last tooth or wheel that touches the coating.

Formula to estimate WFT:

[ \text{WFT} = \frac{\text{DFT}}{\text{Volume Solids Fraction}} ]

For example, if a paint has 50% volume solids and you need a DFT of 100 µm:

[ \text{WFT} = \frac{100}{0.5} = 200 \, \mu m ]

Understanding and controlling WFT is essential for professional painters and contractors to ensure compliance with manufacturer specifications and to deliver high-quality, long-lasting finishes.