I suppose I should also point out that the taller the column of wax in proportion to the surface area, the more concentrated the sludge on the bottom is. In other words, a 1/4" thick layer of wax over a 12" square 2" deep pan will waste more wax scraping the crud off the bottom than the same wax poured into a 4" by 4" by 10" tall paper milk carton.
I like the half gallon milk cartons.