cathammer wrote:I really don’t see the advantage over a straight-sided pot with the same diameter as upper part of this one. In fact, it seems that a straight pot would have the same “evaporative area”, would be more stable, and would have a larger base to allow the application of more heat.
[QUOTE=vladistov, post:16, topic:364239]
No, in ratio to volume it doesn’t. The sloping sides prevent boiling over by allowing heat to escape. Imagine the inverse, and what should happen with less surface area to volume; the heat could not escape and should build up pressure as in a nozzle. A pot with straight sides is in the middle of these extremes, and offers a moderate, and not equal, result. Elementary physics.
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You’re looking at it wrong; remember, we are comparing pots with the same (maximum) diameter at the top. On a straight-sided pot, that maximum diameter & surface area to dissipate heat is available at any level (volume) in the pot, top to bottom. On a downward-tapered pot, the surface area declines as the volume drops, so it actually has an increasingly inferior surface to volume ratio, compared to straight-side, at any point where its diameter falls below the maximum top diameter.
For example, let’s say the two pots are both 10” in diameter at the top (78.5 sq. in. surface). With 8 qts. of liquid in each (filled to top), they would both have the maximum surface area and same ratio to volume: 78.5sq.in./8qt = 9.8 sq. in. per quart. With 4 qts. In each, the straight pot still has the same surface area, so its sq.in. per qt. ratio would be 78.5/4 = 19.6. At that volume, the tapered pot’s diameter will have dropped. If it’s now 8”, say, the surface area would be 50 sq.in., and its ratio would be 50/4, or 12.5…only 64% of the 19.6 ratio of straight-side. If you have one quart in each, and the tapered pot were 6” in diam. (28 sq.in. surface) at that point, the straight pot would have a ratio of 78.5/1 = 78.5, while tapered would have 28/1= 28, almost 2/3 less than straight-side.
To make things worse, from a practical standpoint, to apply the same amount of heat to the contents of each pot would require a more intense application to the caldero because of its smaller base area, which would increase the danger of scorching the contents. To be efficient, it would also require a smaller diameter heat source (stove “eye”) to cut down on the tendency of available heat to “wrap around” the smaller base and be lost.
For what it’s worth, straight-side pots with thicker aluminum sides (matching the bottom) and metal lids (preferably thicker as well…I have some Magna-lites with cast tops) more closely mimic the function of a (cast iron) Dutch oven than this caldero. The larger bottom on a straight-side also makes it easier to brown roasts prior to braising or brown larger quantities of sausage for gumbo, etc.
My suspicions are that the caldero developed for use in more “primitive” kitchens where its tapered shape would have permitted it to sit in a round hole and be stable. Think of a metal tripod with a ring at the top which fits the pot partway down, and holds it over a fire or coals…A metal or stone slab with a hole and spanning a shelf to hold the fire would work the same way. These types of are setups are seen in some pretty ancient kitchen arrangements.