by Ron Joseph
March, 2004
VOC for the Lube
Q. Please show me the stepwise calculations to calculate the VOC's minus water
% True VOC's = 2.23 lb/gal
% Wt Water = 53.0%
% Wt Solids = 20.8%
Density = 8.52
A. Thanks for sending me the information. For reasons that I don't have time
to explain right now, the equation for calculating VOC (lbs/gal) less water
is as follows:
VOC (g/L)
(less water) = (100  %Wt. solids  %Wt. water) x Dc
{1  %Wt water x Dc}
Dw
Where Dc = Density of the coating (g/L). This is the same as the weight per
gallon, (WPG)
Dw = Density of water (G/L) = 8.33 lbs/gal
VOC (g/L)
(less water and exempt) = (100  20.8  53.0) x 8.52
{100  53.0 x 8.52}
8.33
=
223.2
45.79
=
4.87 lbs/gal less water
This is the answer that your vendor gave you and by sheer coincidence
it is just more than double the VOC of the coating including water.
If you need to perform these types of calculations often and want to understand
why we do what we do, then you might want to take my Calculations Class which
will be given again in the last week of September in Rhode Island.
