Is Cast Iron Magnetic?

Yes — cast iron is strongly magnetic, and so is enameled cast iron. Cast iron is an alloy that is overwhelmingly iron: roughly 2 to 4 percent carbon with small amounts of silicon and manganese, and essentially all of the rest is iron. Iron is one of the handful of everyday ferromagnetic elements, so a magnet does not merely stick to a skillet, it grabs it. That single property is behind three practical things: induction compatibility, the magnet test, and a surprising amount of confusion about lookalike cookware.

Why iron is magnetic and aluminum is not

Without going far into physics: in a ferromagnetic material like iron, the magnetic moments of neighboring atoms line up with each other in small regions called domains, and a nearby magnet can persuade those domains to align, which produces a strong attraction. Most metals do not do this. Aluminum, copper and the nickel-rich austenitic stainless steels have no such alignment at room temperature, so a magnet ignores them.

Adding carbon to iron — which is what makes cast iron cast iron — does not change this in any way you would notice at the stove. A cast iron pan behaves, magnetically, like the lump of iron it very nearly is. Neither does a seasoning layer: polymerized oil is a molecule-thin organic film, and it has no effect on magnetism at all.

Which is why cast iron is perfect for induction

An induction cooktop does not get hot by itself. Under the glass is a coil that generates a rapidly alternating magnetic field, and when a ferromagnetic pan sits in that field, the field induces electrical currents in the metal of the pan. The pan’s own resistance turns those currents into heat. The cookware is the heating element, which is why induction is fast and why the hob surface stays comparatively cool.

The consequence is simple: a pan only works on induction if it is magnetic. That rules out aluminum and copper pans (unless they have a magnetic disc bonded to the base) and some stainless grades. Cast iron passes the test more emphatically than almost anything else, and it has a flat, solid base with no cladding layers, so it couples to the field very efficiently.

The real cautions with cast iron on induction are physical rather than electromagnetic: a heavy pan on a glass surface can scratch or, if dropped, crack it, so lift rather than slide. Our guide to cast iron on glass, induction and electric covers the practical rules.

Enamel does not block a magnet

People are often surprised that an enameled Le Creuset or Lodge dutch oven works on induction. It does, and for exactly the reason a bare skillet does: enamel is a thin coat of glass fused onto a cast iron body. The iron is still there, it is still magnetic, and glass is not a magnetic shield. Hold a magnet against the base of an enameled pot and it will stick.

This is worth knowing when you are shopping. “Enameled cast iron” and “induction compatible” are not two features to look for separately — if it is genuinely cast iron under the enamel, induction compatibility comes free. More in what is enameled cast iron.

The magnet test: what it tells you, and what it does not

Take a fridge magnet to the base of a pan and you learn a surprising amount in two seconds.

• A firm, unmistakable grab— cast iron, carbon steel, or a magnetic (ferritic) stainless grade. It will work on induction.
• Nothing at all— aluminum, copper, glass, or a non-magnetic austenitic stainless. It will not work on induction.
• A weak or vague pull— usually a clad or disc-bottomed pan with a thin magnetic layer, or a stainless grade that is only slightly magnetic. It may work on induction, sometimes unreliably or only on certain power levels.

What the test cannot tell you is whichferromagnetic material you have. A magnet grabs cast iron and carbon steel with equal enthusiasm, and those are very different pans — one thick, heavy and heat-retentive, the other thin, light and responsive. Weight and thickness separate them instantly; see cast iron vs carbon steel.

The most useful thing the magnet test does

It catches products that are sold as cast iron and are not. The clearest case is the stovetop waffle iron: a large share of “cast iron waffle makers” are actually cast aluminum, which looks similar in a photograph and behaves completely differently on the stove. A magnet settles it in a second, and so does picking the thing up — aluminum is dramatically lighter for the same size. We go through that category in our cast iron waffle maker roundup, and the metals themselves in cast iron vs cast aluminum.

The same test is handy at a flea market or an estate sale, where an unidentified black pan might be iron, aluminum or something enameled over a light body. If a magnet does not hold, it is not cast iron, whatever the seller says.

The one temperature where iron stops being magnetic

There is a genuine limit, and it is a piece of physics rather than a kitchen concern. Every ferromagnetic material has a Curie point: heat it beyond that temperature and the atomic alignment breaks down, and the material stops being ferromagnetic until it cools again. For iron that point is far above anything a home kitchen produces — hotter than a self-cleaning oven cycle and hotter than a screaming-hot searing pan.

So in practice: your pan will never lose its magnetism while you are cooking, and an induction hob will never mysteriously stop working because the pan got too hot. If an induction hob does stop recognizing a pan, look at warping or a base that is no longer flat against the glass, not at magnetism.

Can a cast iron pan become a magnet?

Weakly, and it is harmless. Ferromagnetic objects can pick up a slight permanent magnetization from repeated exposure to magnetic fields — sitting on an induction hob, or being stored against a magnetic knife strip — which is why an old skillet will occasionally hold a paperclip. It has no effect on cooking, on the seasoning, or on the metal. If it bothers you, it fades on its own over time.

One place it does matter: magnetic induction is also how a hob detects that a pan is present. A pan that is warped or has a raised heat ring may make poor contact and trip the “no pan detected” error even though it is thoroughly magnetic. That is a flatness problem, not a material one — and another argument for the plain, flat-bottomed modern skillets in our skillet roundup.