Made a huge double batch of stock Sunday, portioned it out on Monday into freezer bags. I did all of the portioning at one time into one-cup, two-cup or three-cup portions. The one-cup portions went into pint bags, the two- and three-cup portions into quart bags. I laid them flat, stacked in two piles, in the freezer on Monday night. Last night (Wednesday) I went into the freezer for something else, and the top bag in the pile, a three-cup bag, was not frozen. The bag immediately below was frozen solid. I checked the other bags, and two of the two-cup bags in the middle of the piles (with frozen stock above and below them) were not frozen. All other bags were frozen solid.
As I said, I did the portioning out at one time. I strained the stock before refrigeration, and then I skimmed the fat after refrigeration, so it should have been fairly homogeneous.
So my question is, why would three bags of stock have not frozen when all the others did? I'm hoping someone will have a scientific explanation; otherwise, I might have to blame aliens for messing with my head.