Ask the Expert Question-and-Answer Archive

by Ron Joseph

February, 2004

Calculating VOC of Coating, Less Water and Less Exempt Solvent

Q. Could you please show me how to calculate VOC's with a sample formulation for solventborne and waterborne coatings. I have seen the calculation formula but I never get the same value as the mfr shows on their formulation. Thanks, I really need this info!

A. Thanks for your question, but the answer is more complex than you imagine. If you send me one formulation of a solvent-borne paint and one of a waterborne paint then I'll do the calculations for you. The way you approach the calculations really depends on what data you start with.

For your information, I will be giving a 2 1/2 day environmental calculations class on the East Coast during the last week of September and all of the calculations will be taught at that time. You will not only learn how to calculate VOC in lbs/gal, but also in lbs/gal of solid, as is the new standard that the EPA is promoting in its new regulations.

Please get back to me.

Q. Thank you Ron, I realize the difficulty in calculating VOC in water based formulas due to VOC content in some things like dispersants or thickeners. But generally speaking what calculation do you use. I can never get my numbers to jive with what the mfrs state on their tech data sheets. I can't see how they arrived at 395 g/l on the solventborne formula. I tried applying the CARB calculation and was way off. Help.

A. I performed the calculation (attached Word document) on the first data sheet, and you can read my comments. I hope this will help you do the same for the second data sheet.