according to the plans for the DE, Leonard suggests Minwax Spar Varnish. While at Home Depot the other day, I was going to purchase this , and, just by chance got into a discussion with a paint rep( some outside vendor,not a store employee)....he was there servicing the acct,etc. I was going to buy a gallon sized container and he politely "stopped" me. From what he says....The quart sizes are formulated differently(same product). According to him it has something to do with the VOC % content per ounce. Reason being, he said, was that if the product is shipped as a single container of ONE GALLON, it is somewhat "diluted, or "treated" so that the VOC % falls within a lower..."acceptable" margain,therefore it does not require a "hazmat" charge in most states. He also said that while the product is otherwise identical in use and coverage, some air bubbles seem to appear when initially brushing the product on...requiring a bit more brushing. This is why, he says, the product is also offered in "case" lots of 4 qts( full strength ??) . Well...............with all the caveats in life today....how can I know if this is true? The story seems plausible,and the "math" says it is the same price/ounce...who knows. SOOOOOO, I bought 2qts just for giggles. Is this another "URBAN LEGEND"? who knows. BUT, since Im not a chemical engineer, I sort of took his word that this is true. I cant see where he had a dog-in-this-fight either way... Just thought I'd toss this tidbit in and you can call it BS, or give some credence to it...your call.