by Ron Joseph
Converting Dry Film Thickness to Wet Film Thickness
Q. Is there a formula to convert dry film thickness into wet mils. Most
all of the data sheets we get tell us how many dry mils to apply, I'm not sure
how to convert dry to wet mils.
A. The calculation is very simple:
Wet film thickness =
Dry Film Thickness
Percent volume solids
You will find this information on the MSDS and it might apear as "Volume
solids" or as "Volume non-volatiles".
Dry film thickness required = 1.5 mils
Volume solids = 42%
WFT = 1.5/0.42 = 3.57 mils.
Some words of caution:
1. If you decide to add thinners to the paint you will need to adjust the volume
solids in the denominator accordingly.
2. When you measure the wet film thickenss you must do so immediately after
you have applied the coating. If the coating has a high concentration of very
volatile solvents, they will start to evaporate and you will get erroneous readings.
Therefore, the sooner you perform the measurement, the better.