Raised centers in cookware
I am curious. I bought an All Clad frying pan last fall at Sur Le Table. there is a dimple in the center, which i understand is how they make them. but after using the pan for a while i finally got so pissed at cooking in the middle of a mote I put in the garage, where it is collecting dust.
Today I bought a sur Le Table 5 qt. Braiser on sale for $70. Brought it home and realized that the entire center is raised. Since it is unused i will return it.
But what is with all this raised center stuff? I want a FLAT surface at the bottom of my pan. I don't want to have to cook in the middle of a mote. Mauvel's pans are stainless lined and they are flat. All my other enameled cast iron braisers are flat. What's the deal?
The moat may not be structural. McGee's article on frying pans http://www.nytimes.com/2008/10/08/din... contains this passage about the Benard-Marangoni convection effect:
"As the temperature of the pan surface rose above 350 degrees, the oil began to move and form thick ridges and thin troughs, a stage that some recipes refer to as the oil “rippling.” As the temperature kept climbing, the thin areas spread out and the ridges became fewer and higher. The pattern reminded me of the long drops that run down the inside of a glass of wine or spirits. Eventually the thin areas seemed to run completely dry, and most of the oil had collected in a ring around the pan edge.
With some research, I soon learned that I had been observing Bénard-Marangoni convection, which is related to Marangoni convection in a wineglass. Uneven temperatures at the pan surface cause regional differences in the oil’s surface tension, and this causes the oil to get pulled toward the cooler areas.
I saw the same thing happen on each pan. The hot areas near the pan center end up with thinner and thinner coatings of oil. And the combination of high heat and thinning oil means food is more likely to stick. But the thinning and sticking are unpredictable: they depend on the burner heat, how the pan is placed over it, how much oil you start with, how much you even out the oil by stirring and scraping.
What can we do to work around the curse of Bénard-Marangoni convection? Here’s what I came up with, and if you have a pan that sticks at high heat, you might try it. Add enough oil to coat the pan surface and the food completely. As little as a half-teaspoon of oil will coat a medium sauté pan (for fat watchers, that’s just 20 calories) for cooking eggs and pieces of fish; for chopped vegetables, triple that to coat the additional surface area of the little pieces. Heat the pan until the oil ripples. Then turn the heat down, tilt the pan to even out the troughs and ridges, and wait until it cools just enough that the oil layer stays mostly flat. Then add the food, and let it cook for some time before turning the heat up again. If possible, keep the food and oil moving around."
What I am suggesting is that perhaps you THINK the center is raised, when it's not, because you are seeing the Benard-Marangoni convection and assume the oil is flowing downhill to the side of the pan.
Maybe this is also what was happening with the moat in the roasting pan you posted about on a different thread.
FWIW, you can correct an error like "mote" within a 2hr window of posting. Hover below your post and click the "edit" button when it appears.
Thanks. Too late to change the spelling.
It could be happening with the frying pan, but the roasting pan, no. I put water in it, no heat, just cold water, and it is clearly higher in the middle and tapers off to the edges. I'll check again before returning, because otherwise I like the pan.
Thanks for the info.
With all due deference to Harold McGee, he knows nothing about your pan(s), and you know (or are in a position to know) quite a bit. For instance, only you know whether your pan is actually center-domed when at cooking temperature. How can you know that? By laying a short metal straightedge across the floor of the pan.
This is not an infrequent complaint about pans, and all the complaints are not attributable to mistaking Bénard-Marangoni convection in the fat for deformation of the bottom. Both can and do happen.
Some clad makers strive to make their pans dead-flat regardless of them being ambient temperature or at cooking heats. Not many of them succeed (Demeyere comes very close with theirs, and brags about it). Other makers recognize that they can't keep them flat across the whole temperature spectrum, and so try to make them so that they may not be perfectly flat at room temp, but will deform *to* flat at cooking temperatures. Others make them flat and just hope they don't deform enough to piss people off.
If you think about it, keeping thin layers of different materials with different coefficients of expansion formed and bonded together without any appreciable deformation in use is quite difficult. Especially when certain layers are necessarily thin, others thick, others magnetic, and some of which don't naturally bond to others. Therein lies the *respectable* science of the panmakers and their engineers.
Straight-gauge pans have fewer hurdles to get over to stay flat from/during cooking, but they all can warp and dome/crater if unrelieved stresses from manufacturing suddenly get relieved.
The only solution for clad is to buy the buy the best you can find.