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Feb 16, 2011 05:12 PM

Why isn't my SS cookware magnetic?

So I have 2 old Faberware pots that say "Aluminum Clad Stainless Steel" on the bottom. Since I plan on switching to induction, I have been running around with a magnet taking stock of my equipment. These pots are not magnetic. Does anyone know why?

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  1. Because not all stainless steels are magnetic. For example, 18/10 stainless steel is non-magnetic (if you investigate really hard, it is, but very faint)

    4 Replies
      1. re: E_M

        .... actually these non-magnetic stainless steel are/were considered HIGHER quality for flatware as well as cookware. Unless, of course, if the person is looking for an induction cooking, then they are inferior -- as in your case.

        1. re: Chemicalkinetics

          It is common to use 18/10 for the body of the pot, and bond a magnetic layer on the base.

    1. That's why s/s fridge doors are magnet-free.

      1. The original comment has been removed
        1. E_M: It's all in the alloy and the detection circuitry of your new induction top.

          If you plan to keep your cookware, take it all to a showroom that has a demonstration model of your make & model, and TEST them. This is the only way to be sure of compatibility. I suppose if you wanted to be thorough about it, you'd also compare your stuff to a known reference that works *well* on your intended cooktop.

          I really think the induction manufacturers could increase sales and minimize uncertainty and hard feelings if they simply included a converter disk with every stovetop. Seems like common sense to me...

          11 Replies
          1. re: kaleokahu

            Are you implying that some non-magnetic SS cookware works on one brand of Induction cooktop and not on another?

            The usual claim is that if the pan is magnetic (a modest size magnet, such as a kitchen door one, will stick to it), then it will work on an Induction stove.

            I have a partial counter example - a nonmagnetic SS mixing bowl that works just fine on an induction burner.

            Anyways, for the OP. Most induction compatible SS cookware has an extra layer of steel bonded to the base, one the does react to the burner. That layer often has a sharp corner (as opposed to rounded like the inside of a pan), though I'm sure that's not a requirement. It will also say induction-compatible and/or have a symbol such as a coil. European designed pots are more likely to have this.

            1. re: paulj

              paulj: What I am saying and implying is that the different manufacturers of the cooktops have different designs, electronics and sensors. There are cases like yours reported here where pans that will not respond to a household magnet will work (read: with the poster's cooktop). Likewise, it's reported that some pans that do attract the same magnet will not work (same proviso).

              I'd also like to observe that it may not be as binary an analysis as these discussions suggest. That is, I doubt that it is as simple as works/doesn't work. Yes, the pan has to trip the detection circuitry to persuade the cooktop to energize the coil in the first place. But as we round first base, I think we have to look at whether all degrees of magnetism in the materials alloys produce heat equally well. Your counterexample suggests so, since I think your bowl is in fact very weakly magnetic. But I am not sure that a more ferromagnetic alloy bowl that is otherwise the same would perform exactly the same.

              What I'm pondering here is that, when a manufacturer claims "Induction Compatible" for a ware, what does that really mean? That it will or is likely to be detected? That if detected it will heat? That it will heat to a certain % of the theoretical output of the hob? What latitude is there between tripping the detector and maximum energy transfer? If someone knows if the EU or the Cookware Manufacturer's Assn. or other body has standards for these claims, I'd like to read them.

              1. re: kaleokahu

                My guess is that the detection circuit is there, primarily to protect the cooktop itself. Some electronics can damage themselves if run without a load. But I'm quite rusty on the subject.

                Secondarily the detection circuits should reduce user frustration. You don't want to put a pan on the burner, and then wonder why it isn't hot after 5 minutes of use.

                As far as I know manufacturers are not making claims about how much heat their burners produce in specific pans. The 'heat' ratings are for the power consumed by the unit(s), not BTUs in the pan. Heat production in a pan may be depend on material (carbon steel, SS, etc), thickness, pan shape or area; but I haven't detected any obvious patterns. Cheap enameled steel heats just as well as cast iron or layered SS. That weakly magnetic SS bowl gave me the fastest boil times, though bowl shape may have more to do with that than material.

                Plus, except for limited tasks like boiling water, heat distribution is more important than heat output. And for that, it's hard to beat cast aluminum with a steel insert.

                For the OP, old American SS probably will not work on an induction burner. I have such a pan from around 1990 that does not work on my burner. It wasn't made with that use in mind.

                1. re: paulj

                  "My guess is that the detection circuit is there, primarily to protect the cooktop itself. Some electronics can damage themselves if run without a load"

                  I believe you are right.

                  1. re: Chemicalkinetics

                    Chem and Paul: "...the detection circuit is there, primarily to protect the cooktop itself."

                    There is something to this, yes, but there is also the liability aspect of a magnetic utensil (or ring, watch, toy, etc.) left on the hob. No safety feature, no UL listing, no insurance, no stove business.

                    "[M]anufacturers are not making claims about how much heat their burners produce in specific pans." Yep, and someone should look at this, and we should all wonder why not. The touted 90% efficiency rating is the theoretical max, and if it turns out that it drops significantly with some/all "compatible" cookware, oops, guess we oughtn't say anything. Seems the induction manufacturers are getting a bye, since it is the *pan* that gets hot, not the hob.

                    "...old American SS... 1990" Dang I'm old. The Revereware I'm sending to Lucy is 1950s, and my coffeemaker is c1840!

                    1. re: kaleokahu

                      Exactly how is the 90% efficiency rating measured? 90% of the max power consumption of the whole unit? 90% of the power applied when using that pot?

                      Lets say the magnetic field sets up a weak current in the pan, and thus produce just a small amount heat. What does that do to the current consumption in the burner? If that current is high and generates a lot of heat in the coil, it would be waste heat, and mean low efficiency. But if the current in the coil is also low, then the efficiency can still be high, even though the overall power consumption is less than the rate maximum.

                      On the other hand if you use a converter disk, which gets hot, but the heat transfer from disk to pot is poor, you would end up with a poor efficiency. When efficiency is low, look for heat loss.

                      Compare an incandescent bulb with an LED. A 100w (1750 lm) incandescent may produce more light than a 10W (700lm) LED, but will also be a lot less efficient. You can tell by the amount of heat given off by the two bulbs, as well as the ratio of lm/w

                      To test the efficiency of a burner and pot combination you need to plug the burner into a watt meter, and measure the power consumed while doing a known amount of work, such as raising the temperature of a known mass of water x degrees. The speed at which that is done (boil time) is a measure of power, but not efficiency.

                      1. re: paulj

                        paulj: I don't know how it's measured. It's pretty opaque in the DOE study that originated it and pretty much every induction zealot parrots this 90% number. All I know is that it is a theoretical max. In an earlier thread, I pondered whether the measurement takes into account real-world factors, such as the comparative efficiencies of Induction+SS (or CI) vs. Radiant+Cu--or even Induction+Converter+Cu. No one here knows, and I'm on my way to concluding NO ONE knows, even the boys & girls at DOE. A friend of mine in cookware manufacturing has told me that the CMA (comprised/funded 93% by SS clad corps) don't want this tested.

                        "To test the efficiency of a burner and pot combination you need to plug the burner into a watt meter, and measure the power consumed while doing a known amount of work..."

                        Amen, Brother! My efforts to interest a university applied physics lab in doing such a thing have--so far--come to naught. I might try a crude version of some tests if I could lay hands on a 220VAC watt meter. I have an induction appliance dealer lined up who is willing to let me play on their demonstration units.

                        Oh, and I checked with a couple induction top manufacturers, and they won't tell you the wattage and current numbers for lower hob settings. All they will give you is the max wattage rating.

                        1. re: kaleokahu

                          There's some mention of efficiency studies about half way down this page

                          1. re: paulj

                            paulj: Are you meaning the link that is underscored "established"? I believe that's the original DOE study that keeps getting repeated. I remember no methodology specifics from reading it, but maybe I dozed off... Did you find any?

                            1. re: kaleokahu

                              I was thinking of the 'take a closer look' section, which ends:
                              "In fact, Panasonic states for several of its units that efficiency is 90%, noting that: Heating-efficiency measurements were taken based on standards of the Japanese Electrical Manufacturers' Association and using a Panasonic standard enamelled iron pot. Also: a University of Hong Kong research product showed induction efficiencies from 83.3% to 87.9%, numbers clearly in line with 84% as a minimum and 90% as possible."

                              Of course even if you had reliable efficiency numbers for different stoves, it wouldn't tell you which is cheaper to run - unless you factor in the costs of natural gas and electricity. One is measured in cubic feet (I think - I haven't had gas for a couple of decades), the other KwHr.

                              For me, efficiency matters primarily in the summer when I'd rather not heat up the kitchen more than necessary. Then the induction burner wins hands down over the electric coil stove. I can tell that just by feeling the excess heat radiating from the coil burners.

                              Otherwise, induction is nice because of its responsiveness and control.

                              1. re: paulj

                                paulj: Great. Now I have to chase down the JEMA standards and a "standard" Panasonic pot.

                                You may remember that I live where I actually LIKE a little added kitchen heat most of the year. But I'm still interested in understanding and testing these efficiency claims.

          2. Just to go on a tangent, yes, I have heard that occasionally a magnetic pot (Le Creuset) would not work on an induction (Wolf?) cooktop. Wouldn't this fault lie with the cooktop, since LC works on others? And I believe that Wolf fixed this in subsequent versions, but still. The cooktop has an equal responsibility to work with the pots.

            3 Replies
            1. re: E_M

              I would imagine that many manufacturers of induction stove tops go for a range of required magnetism that allows for a similar response across the different cookware they have tested. They could probably make a wider range of pans/materials work but if that results in one pan on a low setting responding appropriately and another pan set at low but responding like it was on a high setting then we move away from what they are trying to replicate. By eliminating certain metals and alloys they can achieve results that are similar to what is expected using gas or electric stove tops. We can accept differences between materials we cook with but no matter what we cook on we expect somewhat similar results.

              Without limitations imagine all the cook books that would need revision. "Note: If using Bovine Impression or Whackology 3000 cookware on a Quadraquirk or Vapid Industries induction stove top, set heat to medium-low"

              1. re: SanityRemoved

                I imagine the burner applies some power (may be not full) to the induction coil, and senses its response. Without a pan it will respond one way; with a good cooking pot (material, size, etc) another way. If the response is in spec, it moves on to full power; if not, error message.

                1. re: paulj

                  That makes sense to me. I also wonder at what point the amount of power used for a less suitable pan would cause the electric meter to spin faster. In the end it could be cheaper to buy a disc or even induction rated pans.