Ask the Expert Question-and-Answer Archive by Ron Joseph October, 2007 Calculating Weight of Dry Paint Q: I want to paint an aircraft I am building, but weight is a concern. I know I can weigh the paint by the gallon, but does the weight when it dries differ from the weight when it is applied wet? How can I figure this out? A: Refer to the Material Safety Data Sheet (MSDS) where it should tell you the percent weight solids of the paint. Suppose the % Wt solids is 60% and the weight of the paint is 9.0 lbs/gal, then the weight of the solid paint will be 5.4 lbs/gal. If you intend to spray apply the coating to the aircraft using an HVLP spray gun, you can guesstimate that your transfer efficiency will be about 50%. In other words for every gallon of paint that you use, only 2.7 lbs of solid paint is deposited on the aircraft.  The remainder falls to the floor or goes into the filters of a spray booth. Hence, if you know approximately how many gallons of paint you will need to purchase, you can estimate the weight of the solid paint that will be deposited. Regards, Ron Joseph

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