プロフェッショナルとして ネオジム磁石メーカー, I’ve been asked this question more times than I can count: “Is cast iron magnetic?”
It seems like such a simple yes or no question. But as is often the case, the answer is a bit more nuanced.
In this post, we’ll take a detailed look at the magnetic properties of cast iron. I’ll explain exactly why cast iron is, in fact, magnetic. And we’ll explore some of the key factors that impact the magnetism of everyone’s favorite old-timey cookware.

Why There’s Confusion Around Cast Iron and Magnetism
Before we dig into why cast iron は magnetic, it’s worth quickly covering why there’s so much debate around this topic.
Here are the two main reasons people wonder about the magnetism of cast iron:
1. There Are Different Types of Cast Iron
Over the centuries, metallurgists have developed different formulations of cast iron with unique properties.
The most common is gray cast iron. But you also have ductile and malleable cast iron. And even white cast iron.
The exact composition and manufacturing process used to produce these cast iron varieties impacts their magnetic permeability. Generally speaking, gray cast iron is the most magnetic.
But it can get confusing because “cast iron” is often used as a catch-all term for these materials.
When someone asks “is cast iron magnetic?”, it’s not always clear exactly which type they’re referring to.
2. Magnetic Strength Can Vary
Cast iron is rarely perfectly magnetic.
Instead, it exhibits varying levels of 透磁率. This refers to the degree to which a material can be magnetized.
For example, older cast iron pans and vintage cookware often have weaker magnetic properties. This is especially true for pieces manufactured overseas with lower grade materials.
Modern cast iron produced in the US generally has higher and more consistent levels of magnetism. But there can still be variances depending on factors like:
- Composition
- Production method
- Quality control
So while cast iron する have innate magnetic properties, the strength of magnetism can fluctuate.
This variability is why some people claim that cast iron isn’t magnetic, while others insist that it is.
When you account for differences in manufacturing and changes in magnetism over time, you begin to understand the roots of this age-old disagreement.
Now, with all that covered, let’s look at why cast iron and magnets are in fact attracted to each other.
Cast Iron Is Magnetic Because of Its High Iron Content
Cast iron gets its name because it’s made by pouring (or casting) molten iron into molds.
The “cast” part should make it pretty obvious that this versatile material contains a lot of iron.
Is cast iron magnetic? Absolutely! Cast iron owes its magnetism to extremely high iron content exceeding 90% Fe. After all, one of the key characteristics of iron is its magnetism.
To better understand the magnetism of cast iron, it’s useful to first review why iron itself is magnetic:
Why Iron Is Magnetic
Iron exhibits a unique atomic structure that allows its atoms to easily be aligned into the uniform patterns required to generate a magnetic field.
Specifically, it’s the alignment of the electrons in iron’s atoms that facilitate this magnetization.
In isolation, the electrons of an iron atom spin in random directions, cancelling out each other’s magnetic forces.
But when exposed to a strong enough external magnetic force, these electron spins align. It’s this organized arrangement that causes iron to be magnetic.
Now that we’ve reviewed why pure iron is attracted to magnets, it should be clear why iron-rich cast iron shares these magnetic properties.
Cast Iron Contains Over 90% Iron
Cast iron begins its life as an iron ore called “pig iron”. Pig iron is smelted to purity levels exceeding 90% Fe (iron) content before being cast.
After casting, carbon is blended with the iron. But most cast iron maintains an iron composition in excess of 92%.
With that extreme concentration of iron, it’s inevitable that cast iron will share the element’s magnetic qualities.
Now, it’s true that adding 2-4% carbon to pure iron does impact its permeability. But cast iron remains magnetic enough for most practical applications.
What Affects Cast Iron Magnetism?
While all cast iron exhibits some level of magnetism, certain factors impact the strength. Let’s look at why cast iron magnetism varies.
1. Manufacturing Method
One of the main things affecting magnetic strength is production methodology.
Casting involves heating the iron to extremely high temperatures where precise control can be difficult. Things like overheating or uneven cooling can affect permeability.
Generally, consistency in the casting process yields the most magnetic cookware.
2. Alloy Composition
As mentioned earlier, small amounts of carbon and other alloys are added to cast iron. Additional ferroalloys like silicon and manganese can also find their way into some cast iron products.
Too much carbon or other metals interfere with magnetic forces. So composition is another variable affecting magnetism.
3. Quality Control
An often overlooked contributor to variability in cast iron magnetism is quality control.
When manufacturing cast iron overseas, less attention is usually paid to thoroughly removing slag and achieving consistent carbon blending during casting. The result is lower and less predictable magnetic properties batch-to-batch.
4. Cast Iron Variety
Lastly, the variety of cast iron affects magnetic potential. As touched on earlier:
- Gray cast iron is the most magnetic due to its higher iron content and unique flake graphite structure.
- Malleable and ductile iron are moderately magnetic. Ductile iron’s spherical graphite enables better magnetic alignment.
- White cast iron has the lowest magnetic permeability due to its combined carbide structure.
So if someone asks, “Is white cast iron magnetic?”, the answer would be “somewhat”. But less so than gray or ductile iron.
Now that we understand why cast iron is magnetic, how can we test the magnetism of a particular piece?
Testing Cast Iron Magnetism
If you’re on the hunt for cast iron cookware, checking for magnetism is one way to gauge overall quality.
Here are some quick tips on examining magnetic properties:
Use a Strong Magnet
For the best results, seek out a high-powered rare earth magnet. These employ neodymium or samarium cobalt alloys to generate impressive magnetic forces.
A refrigerator magnet probably won’t cut it for reliably testing cast iron.
Try Multiple Contact Points
Don’t just test one part of the cast iron piece. Try attaching the magnet at different points, paying special attention to edges and thinner sections.
Sometimes subtle variations arise across the surface of cast iron products. You want to check for consistency.
Add Some “Vertical Pull”
The strongest test is to hold the magnet perpendicular to the bottom of the cast iron rather than flat against the cooking surface.
When held vertically, the magnet should be strong enough to defy gravity and “hang” from the bottom edge of quality cast iron cookware.
If a vertically-oriented magnet remains firmly affixed around the entire circumference, you can be confident in uniformly excellent magnetic permeability.
Why Cast Iron Magnetism Matters
You might be wondering why minor variations in magnetic properties are worth making such a fuss over.
It comes down to performance and versatility.
Stronger magnetism expands how and where you can use your cast iron.
Induction Cooking Compatibility
The best example is induction cooktop compatibility.
Induction burners rely on magnetic forces to generate heat in pans. Weaker magnetism = slower heating and less even cooking.
So while all cast iron works to some degree on induction ranges, more magnetic pieces deliver better performance.
Multi-Purpose Functionality
If you want to accessorize your cast iron with handy magnetic racks or holders, you need decent magnetism for secure mounting.
Similarly, cast iron skillets with borderline magnetism may not play nice with magnetic knife strips or other storage solutions.
When it comes to versatility around the kitchen, consistent and powerful magnetism is a major asset.
テイクアウェイ
Is cast iron magnetic?The short answer is yes. Cast iron owes its magnetism to extremely high iron content exceeding 90% Fe.
But while inherently magnetic, the exact strength of cast iron magnetism depends on factors like:
- Manufacturing method
- Alloy composition
- Quality control
- Variety of cast iron
Seeking out quality cast iron produced domestically using tightly controlled casting methods will ensure the most consistent and powerful magnetic performance.
And if your piece ever loses its magnetism, a re-enameling service may be able to restore permeability alongside a fresh cooking surface.
So in your search for new cast iron cookware, don’t hesitate to utilize magnetism as a barometer of overall quality and performance.