Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2003

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.

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