Ask the Expert Question-and-Answer Archive

by Ron Joseph

May, 2006

Calculate the Weight of Paint Coating on a Ladder

Q. We are designing a pilot ladder for the military and must keep the weight low. I have been tasked with determining the weight of the paint! I calculated the surface area of the ladder, I know the thickness of the primer and 2 coats of paint, but I cant seem to find the density of paint because it is directly related to VOC and solid percentages, right? Anyway, if I have the Mil-Specs (paint Mil-C-83286, and primer Mil-P-85582) can you tell me the best way to calculate the dry weight of the coating?

A. The weight of the solid paint is given by % Wt solids x Density of coating (lbs/gal). You will find both the % wt. solids and the density of the coating on the MSDS. The density of the coating is sometimes stated as WPG or weight per gallon. If the vendor gives you the specific gravity of the coating (SG) multiply it by 8.33 to convert SG to density (lbs/gal). Therefore, you can now easily calculate the weight solids in a one gallon can of the coating.

ALSO:

Coverage (ft2) = Gals x 1604 ft2/gal/mil x % vol. solids x % transfer efficiency
                                                         Dry film thickness (mils)

In your case transfer efficiency = 100%
Also, you know the surface area of the ladder (ft2) and the dry film thickness of each coat of solid paint. The MSDS usually provides you with the % volume solids, and hence you can now caluclate the number of liquid gals required to cover the ladder.

Armed with all this great information you can now calculate the weight of solid coating for each of the two coatings.

I hope this helps.

Best wishes,

Ron Joseph