you could take a look at cream of wheat (the Quick type). it expands as it cooks quite a bit . so, in a clever mood one morning, i tossed a wad of it into my nalgene bottle and let is simmer all day. that night i ate it for dinner (yumm ..)
well.. here's the deal. it "cooks" a LOT better inside peter than inside a nalgene bottle. and when it does that, it gets Big, and makes a Large Dry Solid Plug.
thusly, about 8 days, a bottle of castor oil, and mostly and entire package of ex-lax later, i was rid of it.
thought i was gonn'a die.