The full form of WFT is Wet Film Thickness.
Understanding Wet Film Thickness (WFT)
Wet Film Thickness (WFT) refers to the measured thickness of a liquid coating after it has been applied, but before it dries or cures. It's a critical measurement in various coating applications to ensure the correct amount of material is being applied. According to our reference, a wet film thickness gauge is essential for accurately measuring WFT during the application process.
Why is WFT important?
Controlling and measuring WFT is important because it directly impacts the performance and durability of the coating. Applying too little coating can lead to inadequate protection, while applying too much can cause issues like:
- Solvent entrapment
- Sags and runs
- Extended drying times
- Poor adhesion
- Increased cost
A suitable WFT ensures that when the coating dries, it achieves the required dry film thickness (DFT), which is a measure of the thickness of the cured coating and is critical for meeting performance standards.
How to measure WFT
WFT is measured using a wet film thickness gauge while the coating is still wet. Different types of gauges are available depending on the type of coating and substrate. The applicator should use these gauges frequently during the application to ensure the average applied thickness is representative of what’s needed.
Types of Wet Film Thickness Gauges
There are several types of wet film thickness gauges, including:
- Comb Gauges: These gauges have notches of varying depths. You press the comb into the wet film, and the lowest notch that touches the coating determines the thickness.
- Wheel Gauges: These gauges use a rotating wheel to measure the film.
- Digital Gauges: Some modern gauges offer digital readings for precise measurements.
The correct use of a WFT gauge ensures the coating is applied in accordance with specifications to meet code requirements.
Practical Insights
- Frequent Checks: Do not measure WFT just once. Regular checks during application are crucial for maintaining consistent thickness.
- Calibration: Make sure the WFT gauge is calibrated correctly to ensure accurate measurements.
- Ambient Conditions: Be aware that temperature and humidity can affect the behavior of liquid coatings, and therefore, WFT readings.
- Application Technique: WFT can be affected by the application technique used, like spray pressure or roller speed. Adjust as needed.
