What Is “Induction Cooking”?
Cooking is the application of heat to food. Food being prepared in the home is very rarely if ever cooked on a rangetop except in or on a cooking vessel of some sort–pot, pan, whatever. Thus, the job of the cooker is not to heat the food but to heat the cooking vessel–which in turn heats and cooks the food. That not only allows the convenient holding of the food–which may be a liquid–it also allows, when we want it, a more gradual or more uniform application of heat to the food by proper design of the cooking vessel.
Cooking has therefore always consisted in generating substantial heat in a way and place that makes it easy to transfer most of that heat to a conveniently placed cooking vessel. Starting from the open fire, mankind has evolved many ways to generate such heat. The two basic methods in modern times have been the chemical and the electrical: one either burns some combustible substance–such as wood, coal, or gas–or one runs an electrical current through a resistance element (that, for instance, is how toasters work), whether in a “coil” or, more recently, inside a halogen-filled bulb.
|Induction is a third method, does not involve generating heat which is then transferred to the cooking vessel, it makes the cooking vessel itself the original generator of the cooking heat.
Microwaving, an oven-only technology, is a fourth method, wherein the heat is generated directly in the food itself.
- How does an induction cooker do that?
Put simply, an induction-cooker element (what on a gas stove would be called a “burner”) is a powerful, high-frequency electromagnet, with the electromagnetism generated by sophisticated electronics in the “element” under the unit’s ceramic surface. When a good-sized piece of magnetic material–such as, for example, a cast-iron skillet–is placed in the magnetic field that the element is generating, the field transfers (“induces”) energy into that metal. That transferred energy causes the metal–the cooking vessel–to become hot. By controlling the strength of the electromagnetic field, we can control the amount of heat being generated in the cooking vessel–and we can change that amount instantaneously.
(To be technical, the field generates a loop current–a flow of electricity–within the metal of which the pot or pan is made, and that current flow through the resistance of the metal generates heat, just as current flowing through the resistance element of a conventional electric range’s coil generates heat; the difference is that here, the heat is generated directly in the pot or pan itself, not in any part of the cooker.)
How Induction Cooking Works:
- The element’s electronics power a coil (the red lines) that produces a high-frequency electromagnetic field (represented by the orange lines).
- That field penetrates the metal of the ferrous (magnetic-material) cooking vessel and sets up a circulating electric current, which generates heat. (But see the note below.)
- The heat generated in the cooking vessel is transferred to the vessel’s contents.
- Nothing outside the vessel is affected by the field–as soon as the vessel is removed from the element, or the element turned off, heat generation stops.
(Note: the process described at #2 above is called an “eddy current”; heat is also generated by another process called “hysteresis”, which is the resistance of the ferrous material to rapid changes in magnetization. The relative contributions of the two effects is highly technical, with some sources emphasizing one and some the other–but the general idea is unaffected: the heat is generated in the cookware.)
(You can see what such a coil and its associated electronics looks like in the image at the right.)
There is thus one point about induction: with current technology, induction cookers require that all your countertop cooking vessels be of a “ferrous” metal (one, such as iron, that will readily sustain a magnetic field). Materials like aluminum, copper, and pyrex are not usable on an induction cooker. But all that means is that you need iron or steel pots and pans. And that is no drawback in absolute terms, for it includes the best kinds of cookware in the world–every top line is full of cookware of all sizes and shapes suitable for use on induction cookers (and virtually all of the lines will boast of it, because induction is so popular with discerning cooks).
(And there are now available so-called “inductions disks” that will allow non-ferrous cookware to be used on an induction element; using such a disk loses many of the advantages of induction–from high efficiency to no waste heat–but those who want or need, say, a glass/pyrex or ceramic pot for some special use, it is possible to use it on an induction cooktop with such a disk.)
On the horizon is newer technology that will apparently work with any metal cooking vessel, including copper and aluminum, but that technology–though already being used in a few units of Japanese manufacture–is probably quite a few years away from maturity and from inclusion in most induction cookers. If you are interested in a new cooktop, it is, in our judgement, not worth waiting for that technology.
(The trick seems to be using a significantly high-frequency field, which is able to induce a current in any metal; ceramic and glass, however, would still be out of the running for cookware even when this new technology arrives–if it ever does.)
Pros and Cons
To serious cooks, the most important favorable point about induction cookers–given that they are as or more “powerful” at heating as any other sort–is that you can adjust the cooking heat instantly and with great precision. Before induction, good cooks, including all professionals, overwhelmingly preferred gas to all other forms of electric cooking for one reason: the substantial “inertia” in ordinary electric cookers–when you adjust the heat setting, the element (coil, halogen heater, whatever) only slowly starts to increase or decrease its temperature. With gas, when you adjust the element setting, the energy flow adjusts instantly.
But with induction cooking the heat level is every bit as instantaneous–and as exact–as with gas, yet with none of the many drawbacks of gas (which we will detail later). Induction elements can be adjusted to increments as fine as the cooker maker cares to supply, just like gas, and–again very important to serious cooks–such elements can run at as low a cooking-heat level as wanted for gentle simmering and suchlike (something even gas is not always good at). Someday, perhaps not so many years away, the world will look back on cooking with gas as we today look on cooking over a coal-burning kitchen stove.
No Wasted Heat
With induction cooking, energy is supplied directly to the cooking vessel by the magnetic field; thus, almost all of the source energy gets transferred to that vessel. With gas or conventional electric cookers (including halogen), the energy is first converted to heat and only then directed to the cooking vessel–with a lot of that heat going to waste heating up your kitchen (and you) instead of heating up your food. (The striking image at the left shows how precisely focussed heat generation is with induction–ice remains unmelted on an induction element that is boiling water!)
As a comparison, 40%–less than half–of the energy in gas gets used to cook, whereas with induction 84% percent of the energy in the electricity used gets used to cook (and the rest is not waste heat as it is with gas). There are two important heat-related consequences of that fact:
- cooler kitchens: of course the cooking vessel and the food itself will radiatesome of their heat into the cooking area–but compared to gas or other forms of electrically powered cooking, induction makes for a much cooler kitchen (recall the old saying: “If you can’t stand the heat, get out of the kitchen.”); and,
- a cool stovetop: that’s right! The stovetop itself barely gets warm except directly under the cooking vessel (and that only from such heat as the cooking vessel bottom transfers). No more burned fingers, no more baked-on spills, no more danger with children around. (The photo at the right–one of several similar ones to be found on the web–shows, like the one above, how only the cooking vessel does the actual cooking.)
We have already mentioned that the stovetop stays cool: that means no burned fingers or hands, for you or–especially–for any small children in the household. And for kitchens that need to take into account special needs, such as wheelchair access, nothing, but nothing, can beat induction for both safety and convenience (see the paragraph farther below).
Furthermore, because its energy is transferred only to relatively massive magnetic materials, you can turn an induction element to “maximum” and place your hand flat over it with no consequences whatever–it will not roast your non-ferrous hand! (Nor any rings or bracelets–the units all have sensors that detect how much ferrous metal is in the area that the magnetic field would occupy, and if it isn’t at least as much as a small pot, they don’t turn on.) And, while an element is actually working, all of its energy goes into the metal cooking vessel right over it–there is none left “floating around” to heat up anything else. (The image at the left shows a hand–wearing a metal ring–harmlessly touching a full-on induction element, while a metal utensil lies equally harmlessly on another, emphatically demonstrating those points.)
Moreover, gas–induction’s only real competition–has special risks of its own, not all of which are as well known as they perhaps should be. While the risk of a gas flame, even a pilot light, blowing out and allowing gas to escape into the house is relatively small, it does exist. But a much bigger concern is simply gas itself, even when everything is working “right”.
Ease and Adaptability of Installation
Unlike most other types of cooking equipment, induction units are typically very thin in the vertical, often requiring not over two inches of depth below the countertop surface. When a cooking area is to be designed to allow wheelchair access, induction makes the matter simple and convenient.
It is an obvious but still very important fact that induction cookers are powered by electricity. Not every home actually has a gas pipeline available to it–for many, the only “gas” option is propane, with the corollary (and ugly, space-taking, potentially hazardous) propane tank and regular truck visits. But everyone has clean, silent, ever-present electricity.
Burning gas has byproducts that are vaporized, but eventually condense on a surface somewhere in the vicinity of the cooktop. Electrical cooking of any kinds eliminates such byproducts.
The Cooking Vessels
The most obvious and famous drawback to induction cooking has already been mentioned: it only works with cooking vessels made of magnetic materials. The commonest such materials used for cooking vessels are stainless steel and cast iron. Cookware suited for use with induction cookers, from the extreme high-quality end down to thrift-store modest, is readily available; but if you already have a stock of mostly expensive aluminum or copper or glass or pyrex cookware and little or no cast iron or stainless, you might be up for a cookware investment.
On the other hand, if you have a significant quantity of non-ferrous cookware that is not terribly expensive, you can replace it–possibly with much better stuff!–as part of the process; cast iron is by no means “spendy” cookware. If you have ever seen the inside of a real restaurant kitchen, you will surely have noticed that most or all of the cookware is either cast iron or nice, shiny stainless steel (even when they are still using gas for their cooking). Steel is most cooks’ preferred cookware material for many good reasons we discuss elsewhere on this site (see the link below–and recall that enamelled steel cookware also works beautifully on induction.
As we noted elsewhere, technology to allow use of any metal cookware–even copper and aluminum–is in the pipeline, but there are definite problems with getting sufficient power levels with that technique, so it will likely be many years before units with it start showing up in the mainstream (if they ever do). So, for now, the need for ferric cookware does remain.
(There are now, however, adaptors available that will allow any pot or pan to be used on an induction element; because they essentially turn an induction element into a standard stovetop type of heater, they lose many of the advantages of induction–they are less efficient, they get very hot, and may be restricted as to maximum power level–but if you have a special-purpose item of non-ferrous cookware, such as glass or ceramic, it can be made to work on induction.)
This is not a valid negative–but we list and discuss it here because there are so many falsehoods and misunderstandings floating around on this matter. With hard numbers, induction cooking units are not merely as powerful as even “pro” gas ranges (residential “pro”, that is), they are almost invariably much more powerful. (And that’s using conservative figures for both gas and induction efficiencies.)
Owing to the length of quoted material involved in our discussion, we have put this topic on a page of its own; but the real scientific literature seems to show rather clearly that there are simply no radiation-associated hazards, even for those with imbedded cardiac devices. The fields are very localized, and in any event the cooking vessel absorbs virtually all of the field energy (and if there is no cooking vessel on an element, it won’t turn on).
Induction itself is a noiseless process: the energy fields are generated by electronic equipment, which is silent. But even efficient electronics generates some heat. Whether the amount of heat generated can be dissipated “passively” (just by radiation and natural air flow, still silent) or requires a small fan to augment the air flow depends in good part on how tightly a given maker has packed how much power into how much space–some units have fans, some don’t. But even on those with fans, one, the fan does not necessarily run all the time–usually just when the unit is running multiple elements at high settings–and two, such fans are normally pretty soft-sounding. There can also an occasional very soft “tick” sound, as the power controller cycles the elements on or off to keep the element power steady and stable.
Cookware of solid cast iron, including enamelware, is not subject to such issues; and clad cookware of the top lines should not be.
If the electricity supply to your home is interrupted, you will be unable to cook; gas supplies can be interrupted, too, but such interruptions are normally somewhat less likely than electricity interruptions. If the electricity where you are frequently goes out for hours at a time, the loss of cooking ability may be an issue for you. Most people living in such circumstances will have provided themselves with a backup, such as a propane-powered emergency generator–but if that’s you and you have no backup, factor the matter into your decisions.
No “Char” Flames
For those to whom charring such items as peppers in an open flame is important, the lack of such a flame is a drawback. (It is, of course, one shared with all non-gas cookers.) But nowadays, most good ovens–gas certainly, but probably even electric–can do an acceptable job of charring food.