CSLB C-33 Painting & DecoratingCoating ApplicationMedium
A painting contractor is preparing to apply a high-build epoxy coating to a concrete floor. The manufacturer specifies a wet film thickness (WFT) of 20-25 mils per coat. The contractor plans to use a notched squeegee designed for 22 mils and then back-roll. What is the expected dry film thickness (DFT) if the epoxy has a solids by volume content of 70%?
- A15.4 - 19.25 mils
- B28.6 - 35.7 mils
- C20.0 - 25.0 mils
- D14.0 - 17.5 mils
Show answer & explanationAnswer & explanation
Correct answer: D. 14.0 - 17.5 mils
To calculate the DFT, multiply the WFT by the solids by volume percentage. For the lower end: 20 mils * 0.70 = 14.0 mils. For the upper end: 25 mils * 0.70 = 17.5 mils. Therefore, the expected DFT range is 14.0 - 17.5 mils.
Why the other options are wrong
- A. This calculation is incorrect; it uses an incorrect WFT range or solids percentage.
- B. This calculation incorrectly divides WFT by solids, which would be used to find WFT from a target DFT.
- C. This option represents the WFT, not the DFT, as the volatile components will evaporate.
Dry Film Thickness (DFT) Calculation
The thickness of a coating film after all volatile components have evaporated, calculated by multiplying the wet film thickness (WFT) by the percentage of solids by volume.
- DFT = WFT × % Solids by Volume.
- Crucial for coating performance, protection, and longevity.
- Measured with a dry film thickness gauge after curing.
Memory trick: Wet film's solids dictate dry film's true size.