My understanding is that as tung oil is used the container should be collapsed to drive out the oxygen in air to maintain the quality of the oil. I cannot find corrugated/collapsible plastic bottles at woodworking stores so I have question if such is even necessary. I have checked at WoodCraft, Klingspor and even googled it, all to no avail. Do NCWW members use such bottles? If so, where did you get them?