Hi Again Pete;

When building kayaks, most posters here mix in 6-12 oz batches, not 1.5 gal at a time . . . My point is that disregarding corrections, the percentage volume difference amounts to about the width of the measuring line on the measuring cup . . . Consequently, metering the volume via a measuring cup is actually no better than weighing it without regard to specific gravity. I'd like to see someone pour resin or hardener into a measuring cup to 30 thousandths of an inch or so accuracy, consistently . . . ;-)

Thinking about it, the problem would be the same with a 1.5 gallon mix, as the measuring bucket is essentially proportional to the small mixing cups, only larger. There, the weighing error would be equivalent to around a tenth of an inch on the graduations.

In any event, a simple calculation can put you dead on if you feel it is that important, as was pointed out in another post.

Grabbing a handful of mashed potatoes, Spidey