One of the flaws in the induction technology (to date) has been wok cooking. Of course, wok coooking on a gas cooktop is nothing to write home about either. To properly perform wok cooking on a gas burner you need at least 30,000 BTU's--and preferably 60,000, otherwise you end up doing mostly high heat steaming, unless you just cook very small quantities. I have used my DIVA DPP-5 induction cooktop under very high heat--about 30,000 + BTU's for stir frying, but you can't use the roundish bottom of a true wok to do this properly, as inuction requires constant contact with the cooking surface. This leads me to another minor flaw with induction cooking, which is that you can't take a pan and shake it around above the surface (as you can with a gas burner and still get some heat). What I generally do when wok cooking is use the gas burner I have out on my deck, a 60,000 BTU unit that is attached to a very expensive Kalamazoo gas grill. The advantage of this is I now have the proper heat and I don't get any splattering indoors or other issues I don't want in my house. I know a couple of people that have really gilded the lily and installed a 60,000 BTU hob next to their gas or induction cooktop. But not many people want the extra expense or to relinquish the extra counter space to this extra hob. This also means you'd have to get a wider and more powerful venting fan. Greg

I believe that the feet of the Demeyere wok help to pass the energy up the sides, similarly to the Gaggenau wok/wok unit/ring (not sure that the Gaggenau ring/wok work (well) on other units). I have a Le Creuset cast iron wok which is flat on the outside and round on the inside. I think Lodge makes one too. The technique for using it is different than for using a traditional thin wok, which doesn't bother me, since, according to my Asian mentors, I'm hopeless with a wok anyway. :) The big problem with it is that the portion that contacts, or is close enough to the cooktop is so small that one can't use the outer, high power, part of the large double ring. The difference for cooking is that it takes a long time for the sides of the wok to heat up. I think it might be more practical to partially warm it in the oven first. Once the whole wok is actually hot it does work very well, at least by my limited abilities. The difference is that it does not cool fast either. There are a lot of techniques that involve cooling the wok and/or food by lifting, tossing, etc., that are out of the question. One could lift and toss, perhaps two handed for the weight, but lifting isn't going to cool cast iron, and while adjusting the setting on the induction will have an effect, it's going to take awhile to cool just as it took awhile to heat. If one does want to cool the food, a better way might be to add bits of frozen peppers, or even ice chips. Most induction units nowadays (including mine) do allow one to lift a pan long enough to toss the contents to mix them without turning off, so that isn't a problem. Again, it's not a one handed flick, but it works fine. For me, the whole point of the wok is the interior shape, so this works well for me. I also have gas (though not blast-o-burner), so I could have a traditional wok. I am no expert at wok cooking, though I know a lot more theory than expertise, and I'm not sure I understand all of the insistence for ever hotter burners. If one is stir frying, I get the point of fast heat recovery, and the need for a certain amount of power to make that happen, but one doesn't want the wok itself to get hot enough to scorch the oil. I was taught, by my home cook friends, not to get the wok too hot. This may be why being able to quickly lift and cook a thin wok is so important. Once it's good and hot, the cast iron wok doesn't have the quick cool down when ingredients are added, and the recovery with induction is pretty good. That is, there isn't the instant heat transfer of the traditional charcoal fire and hand hammered carbon steel, but the wok doesn't cool off instantly either. This is with a smaller, family sized portion, however, not a big ol' party heap. At some point the quantity of ingredients will overwhelm the heat retaining mass of the cast iron.

From what ssdarb reports, it seems that there may be a question about whether the bubble-pattern in the boil-test is the result of an expanded induction field from the burner or instead is the result of heat conducting across the base from the central heated area (what kas called" transverse thermal conduction from the center."). So, following up on what Kas just said, I suggest running the bubble-pattern test with a large cast-iron skillet rather than a thin steel pan. Or, you could use an infra-red thermometer gun if you have one. (Should work well measuring surface temperature distribution across the dark surface of a CI pan.) I'm suggesting cast iron because, in my experience, cast iron pans show heat pretty quickly in the parts of the base that are within an induction field but do not do a good job of conducting heat outward across the base without a lot of preheating for a fairly long time. IIRC, the Bosch cooktop's outer ring marking is for 11" and the inner ring marking is for something like 7" or so. A 12" cast-iron skillet will have a base that is around 10" across and should be sufficient to see whether there is an expanded boil pattern from being within the burner field. (You also could do this with a big carbon steel skillet but you probably need a larger one --- cs pans generally have much wider flaring sides and correspondingly smaller base diamters, so a 12" cs pan might have only an 8½" base). I'm suggesting these kinds of pans because if anything is going to react to an induction field, it will be CI and CS pans. If the boil pattern expands across the base from the inner ring's area within a minute or so, the big burner is producing a wider field more or less matching the ring markings on the glass top. If takes several minutes to get bubbles in what Kas called the annular area -- and maybe it never happens if the field is only in the 7" area --- then the Bosch's big burner is not producing the advertised heating area. If it is somewhere in-between, there may be a problem with the induction coil. I think it is possible to have a two-ring ring system as Kas discussed --- manufacturers having been doing that for years with radiant electric burners --- but it seems to me to be unnecessary with with induction's "built-in" pan sensing. Seems to me that, if the field is supposed to be strong out to 10 or 11 inches, and is not, then there's a problem with coil and a warranty service call would be appropriate. As an aside, the notion of "automatic pan size sensing" is . . . well, it seems to me that the notion is just marketing blather. An induction burner will only heat metal within the area of the field, right? Use a pan smaller than the field size, and only the pan is heated (down to a certain minimum pan size below which there is insufficient mass to allow the burner to operate.) So the burner has adjusted to pan size, right? Put a bigger pan on that burner and the large pan is heated out to the edges of the field strength. No need for sensors for that kind of "magic" adjustment to pan size, eh?

Thanks Toronto Veternarian. Another advantge of a rounded bottom is that you can quick cook everything with super hot oil on the bottom, thus preserving the flavor. And then you can let the oil drain from the food on the sides. A wok with a small flat bottom can achieve the same thing as a rounded bottom wok,, but one with a flat bootom that exceeds 6 1/2" will necessarily have the sides be so steep that food will slide down. By the way, I would love to have someone who have used a 15,000 BTU butane burner and a 1,800 Watt induction burner compare the two for wok cooikng using a 6" diameter flat bottom carbon steel (or cast iron) wok.