I started doing this , as a means of stacking leftovers in the fridge. Many of the pots that I use are too large to fit the fridge comfortably, and I was running out of smaller pots, since they were all sitting in the fridge, sometimes only a quarter full. Using the bowl and saucer method, I sometimes stack things five layers high. This works best for things that aren't going to leak everywhere.
This morning I made a giant pot of gravy. There is also leftover meat, potatoes and vegetables. I generally remove several bowls at once. One that contains just the right amount of something , is used for that meal. Stuff from the other bowls is scooped into it, and then that bowl is placed in the microwave. This saves on dishes, since eventually each fridge bowl, is used to eat from.
Stacking bowls works equally well in the freezer. Those with plenty of taper, are less likely to be damaged in the freezer. Bowls with vertical sides are more likely to be split apart as the food freezes. In order to manage the space well, it helps to have many bowls and saucers of different sizes, to match various batch sizes of things to be frozen. Some freezer space may be wasted, but provided that you have plenty of space, this is an excellent way to avoid plastic and to avoid having a whole lot of dirty containers to wash.
I don't know that this would work for long-term storage, but it works just fine as a means of managing leftovers. Whenever I find a really good deal on something, I tend to cook it all up at once, and then freeze it in convenient sized portions.
If something is to be kept for a longer period, the bowl can be removed from the freezer after the food is frozen. Pour some water on it then quickly pour it off again. The food will now have a thin layer of ice, separating it from the dry air of the freezer.
Yard sales and free piles by the side of the road , contain a limitless supply of bowls and saucers. There is no need to look for matching sets. Almost any saucer the right size, will provide an adequate seal for a similarly sized bowl. About $0.25 each sounds right for bowls. The world is swimming in unmatched saucers. I wouldn't pay more than a nickel.
My sister in the US uses these little Pryex glass bowls exactly as you say, and they have plastic lids. The dishes can go in the freezer, fridge, microwave, or into her bag to take to work for lunch, and they're an okay shape to eat from.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
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