I made a recipe recently which called for dried ground orange peel. Rather than buy some, we dried some orange peels and I ran 'em through the spice grinder. I ground more than we needed, and we are out of glass spice jars, so we put the ground peel in a disposable plastic container (like the ones that come with salad dressing at some restaurants). The following day, Stacy noticed that the container melted:
The bottom of the cup actually "melted;" it got stuck to the top of the spice rack. It wasn't due to heat, I don't think. The plastic kind of went mushy and soft; the bits melted on to the top of the rack could be wiped off!
Here's a shot of the bottom of the thing after we peeled it off:
It was so soft, you could mush in the sides:
I honestly have no idea what caused this, but if anyone has ideas, I'd love to hear 'em!