If you're shopping for clad stainless steel cookware, you're probably asking yourself: 3-ply or 5-ply? And what's the difference, anyway--and how much does it matter?
It's not rocket science, but understanding the differences will be hugely helpful in selecting the best cookware for YOUR needs. We'll explain the differences and tell you how to pick out a good, high quality set of clad stainless steel cookware. (Hint: The number of plies is irrelevant compared to other factors--read on to find out why.)
Clad Stainless Steel Cookware: An Introduction to Plies
Diagram of a 3-ply pan (by All-Clad).
According to Wikipedia:
Cladding is the application of one material over another to provide a skin or layer.
Cladding can apply to all kinds of materials. In cookware, cladding is the process of bonding different metals together. Plies are the layers of metals in a clad pan.
Cladding can also be called bonding, especially when referring to metals.
So, a 3-ply (also called tri-ply) pan has three layers of different metals. In nearly all cases, the outer layers are stainless steel and the inner layer (called the heating core) is aluminum (as shown in the All-Clad diagram above). A 5-ply pan can have different materials, but the idea is the same: two outer layers of stainless steel that protect 3 inner layers of heating core.
Why this configuration? Stainless steel is durable, but doesn't heat well. It protects the heating core, which is typically aluminum or copper, both of which have excellent heating properties but aren't as durable or stable as stainless steel. Thus, clad pans offer durability and stability and an efficient heating core.
Bonded metals have existed for decades, but John Ulam, founder of the All-Clad cookware company, was the first to use bonded metal to make cookware. The company originally made other products out of bonded metal, then one day Ulam used bonded metal to make a pan for his personal use. He liked it so much he began making pans for friends, then began selling them at local fairs and cookware shows. The pans were a huge success and by 1971, All-Clad was exclusively a cookware company.
Ulam's first clad cookware was 2-ply: it had a thick exterior layer of aluminum bonded to a stainless steel cooking surface. This was the All-Clad Master Chef line (sadly now discontinued). His most popular product, tri-ply cookware, came along a bit later, and the rest is history.
The Outer Layers
While the Master Chef 2-ply cookware was excellent, most clad cookware on the market today is either 3-ply or 5-ply. Let's take a closer look at the cooking surface, the exterior surface, and the heating core that these outer layers protect.
Cooking Surface
The cooking surface has to be durable and safe (non-reactive), so it's usually made out of a 300 grade stainless steel. The most common steel used is 304 and either 18/8 or 18/10 steel. Both are high quality "surgical" stainless steels. The numbers mean that the steel is 18% chromium and either 8% or 10% nickel. "Surgical" is largely a marketing term that means the steel is corrosion (and rust) resistant.
Most brands of clad stainless cookware have an 18/8 or 18/10 cooking surface, including All-Clad, Demeyere, Tramontina, and Cuisinart Multiclad Pro (all brands we recommend; links go to our reviews).
Another grade of steel used in clad cookware is 316Ti, which contains a small amount of titanium in it (about 0.5%). Titanium increases corrosion resistance slightly, although 304 steel is durable enough and corrosion resistant enough for kitchen use. 316Ti cookware can be more expensive without adding a lot of benefit, but some people love it. Two brands that use 316Ti are Heritage Steel and Saladmaster (links go to our reviews).
(Incidentally, some people believe that 316Ti steel doesn't leach any nickel or chromium, but it leaches these elements at about the same rate as 304 steel. In both cases the amounts are small and not at all unsafe.)
On cheaper clad cookware, you sometimes see lower grades of steels such as 200 grade and 400 grade steel (400 is also called 18/0), on both the inner and outer layers of steel. 200 grade steel uses manganese rather than nickel for corrosion resistance, and 400 grade is free of both nickel and manganese (which is what makes it magnetic for induction compatibility). Both 200 and 400 grade steels are less corrosion resistant than 300 grade steels, but they're cheaper, which is why you see them on lower-priced stainless cookware.
Some people prefer 400 grade steel cookware if they have a nickel sensitivity and are trying to avoid it (although it's unlikely the small amounts in cookware have much of an effect on your nickel intake). 200 grade steel is less common, and if people buy it, they usually don't know they're buying it. You'll see it on inexpensive brands of cookware that usually don't name the type of steel used, or do so in the small print that's hard to find.
If the price of clad stainless steel cookware is too good to be true, check the type of steel it's made of: all 400 and 200 grade steels are cheaper and less corrosion resistant than any 300 grade steel.
Exterior Surface
The exterior surface of clad cookware--the side in contact with the heating source--is usually a 400 grade steel, also called 18/0. This steel is nickel-free, which makes it ferritic (i.e., magnetic), so it's induction compatible. There are different grades of 400 steel, some more corrosion resistant than others, but all are less corrosion resistant than 300 grade steel.
400 grade steel is often called "magnetic steel," as in the All-Clad diagram above, so you know that it's induction compatible. The vast majority of induction compatible steel in cookware is 400 grade.
Heating Core
The exterior layers of steel protect the softer, less durable layer(s) of aluminum and/or copper, which are necessary for spreading heat evenly. Since the heating core is so important when selecting cookware, it has its own more detailed section below.
Is Stainless Steel a Safe Cooking Surface?
Both 18/10 and 316Ti steel leach very small amounts of nickel and chromium into your food, especially when new. The leaching is not in unsafe amounts, and decreases with use, eventually stopping altogether.
Some people mistakenly believe that 316Ti steel does not leach nickel or chromium, but as we said above, that is not the case. In fact, some studies have shown that 316Ti leached them in slightly larger amounts than 304 steels.
If you're concerned about new stainless cookware leaching nickel or chromium, you can simmer it with acidic water (add a bit of vinegar) for a few hours. This removes most of it.
However, unless you have a nickel allergy, this isn't necessary. Even with the small amounts of leaching, stainless steel is one of the safest, most non-reactive surfaces you can cook on.
The Heating Core: The Core Issue
The heating core comprises the inner layer(s) that allow cookware to spread heat quickly and evenly. It is usually aluminum (1-3 layers, depending on the total number of plies) because aluminum has excellent heating properties and is inexpensive. You may also see copper, but only in 5-ply cookware because copper doesn't bond well to steel so you almost always see it in combination with aluminum. We talk more about different 5-ply configurations below.
Assuming the exterior is good quality (i.e., 300 grade) stainless steel, the heating core is the most important feature of clad cookware because it determines how well the cookware performs. And the most important aspect of the heating core is its thickness.
In fact, the thickness of the heating core is more important than the number of plies.
A thick heating core spreads heat more evenly and holds heat longer than a thin one. Whether one layer of aluminum, three layers or aluminum, or a combination of aluminum and copper, you want a heating core that's thick enough to heat evenly and hold heat well.
We get into specifics below.
Assuming the exterior of clad cookware is 300 grade steel (which most is), the heating core is the most important feature to consider when buying clad cookware--and the most important aspect of the heating core is NOT the number of plies, but rather, its overall thickness.
Why Different Steel Is Used for the Interior and Exterior of a Pan
As stated above, nickel-free steel (18/0 or any 400 grade) is not as corrosion resistant as steel with nickel (18/8, 18/10, and 316Ti), but nickel makes steel non-magnetic, and being magnetic is required for induction compatibility. The highest quality, longest lasting cookware usually has a 300 grade cooking surface and a 400 grade or 18/0 exterior.
Older clad stainless cookware, made before about the mid-1990s, may not have a magnetic layer for induction cooking. This cookware is usually 100% 300 grade steel because it's more corrosion resistant, and induction compatibility was less of a concern because induction stoves were quite rare then.
Why Plies Aren't That Important
Many people assume that 5-ply cookware is always thicker than tri-ply, but this is not always the case. For example, All-Clad D5 is the same thickness as All-Clad D3, and All-Clad Copper Core, which is 5-ply, is even thinner than All-Clad D3 (because it takes half as much copper to produce the same heating performance as aluminum).
The gold standard for heating performance has been All-Clad D3 for decades. It has an aluminum heating core 1.7mm thick. This is enough aluminum to provide fast, even heating and good heat retention, but not so thick that it makes the cookware uncomfortably heavy.
If you can handle heavier cookware, a thicker heating core will provide even more even heating and longer heat retention. One such brand is Demeyere Industry, which is 5-ply cookware that has a 2.1mm thick heating core that's 3 layers of aluminum. Misen also offers a 5-ply with 3 inner layers of aluminum that's about as thick as Industry.
They are heavier than All-Clad D3 (and D5), but not by a lot, so if you can handle the slightly extra weight, these are both excellent choices.
How do you know how thick a heating core is? This can be tricky, because makers don't always disclose this information. You can sometimes find the information on the manufacturer's website, on Amazon, or on review sites like this one. You can also usually tell by the thickness and weight of the cookware, although that can be tricky unless you're able to do a side-by-side comparison.
The number of plies isn't as important as the overall thickness of the heating core--and yes, some 5-ply cookware can be as thin or even thinner than some 3-ply cookware.
You also need to know the material, because it takes less copper to produce the same heating performance as aluminum (about half as much).
Pay attention to the overall thickness, weight, and material(s)--not the number of plies.
Types of 3-Ply Cookware
Tri-ply cookware diagram.
There's just one type of 3-ply, or tri-ply, cookware. It has outer layers of stainless steel with an aluminum heating core.
We've never seen a tri-ply with a copper heating core because of the bonding issue. If you do find such a product, we don't recommend buying it (unless the maker has come up with new, more effective cladding technology we're not aware of).
Types of 5-Ply Cookware (And "5-Ply" Cookware)
With 5-ply cookware, the options get a little more complicated.
They are:
Let's look at each type.
S-A-A-A-S
Demeyere Industry 5 diagram.
Stainless-aluminum-aluminum-aluminum-stainless. Three internal layers of aluminum is the most common 5-ply heating core, seen in most brands of 5-ply cookware except All-Clad. Typically, the core layer is pure aluminum, which heats more efficiently, with two thin layers of an aluminum alloy that bonds better to steel.
A lot of people like to say that 5-ply with three aluminum layers is glorified 3-ply, but because the aluminum layers are different alloys, it really is a 5-ply product. It's a distinction that isn't nearly as important as (again) the overall thickness of the heating core.
S-A-C-A-S
All-Clad Copper Core diagram.
Stainless-aluminum-copper-aluminum-stainless. A copper core almost always has two very thin outer layers of aluminum, which are there because they form a better bond better to the steel than copper. This is less common than an all-aluminum heating core, and usually more expensive.
All-Clad Copper Core is by far the most well known copper core cookware, but there are a few knockoffs out there that sell for less. It can be difficult to know how thick the copper layer is in these knockoff brands unless someone has actually cut the pan open and measured it. A lower price usually means less copper, or it could mean the cookware was made overseas (and has heating properties very similar to All-Clad Copper Core). Without having done this, it's hard for us to make comparisons (and we haven't tested or reviewed any other copper core cookware yet).
S-A-S-A-S
All-Clad D5 diagram.
Stainless-aluminum-stainless-aluminum-stainless. Rather than three layers of aluminum, the All-Clad D5 heating core is two layers of aluminum around an inner core of steel. We're not huge fans of D5 because stainless steel has terrible heating properties--the whole reason clad cookware was invented in the first place. So why add another layer of steel? All-Clad says the internal layer of steel slows down the lateral movement of heat (that is, from burner to pan to food), allowing the pan to heat more evenly, especially on induction (which heats very quickly). While there's some truth to this, the differences are quite small, and in most cases unnoticeable during actual use.
Many people assume that D5 is thicker than D3, but it isn't. They're the same thickness, which means that D5 has less aluminum D3. Since aluminum is what spreads heat evenly, it doesn't make a lot of sense (to us) to have less of it--and in a more expensive product, to boot. If D5 had more aluminum plus the steel layer, it would be a much more interesting product. But with less aluminum and more steel than D3, we think D5 is overpriced and overhyped. Because of the extra steel, D5 is also heavier than D3, but without offering an improved heating core (like 5-ply Misen, Demeyere Industry, and Heritage Steel do, for example).
Some people think the internal layer of steel is magnetic to improve induction performance, but our research shows that it is standard 18/10 steel, which is not magnetic. And since the speed of induction is a large part of its appeal, we don't understand the logic behind slowing that down with an extra layer of steel (a thicker core layer of aluminum would also slow down heating, as well as offer more evenness and similar heat retention).
Since D3 is cheaper and contains more aluminum, we recommend it over D5.
If you want more details, see our article D3 Vs. D5: Which Is Better?
What to Look For in Clad Cookware
Whether you buy tri-py or 5-ply, you shop for the same basic features.
Thickness (Including Exterior Layers and Heating Core)
In general, the thicker cookware is, the better it's going to heat--that is, more evenly and with longer heat retention. This is true of all cookware, not just clad stainless.
It's especially true for clad stainless steel cookware, though, because makers don't always disclose the thickness of the heating core. If you don't have this information, it's hard to go wrong with the thicker, heavier choice (though we do recommend doing the research to find out exactly what you're buying--good quality clad stainless cookware is not cheap).
As we said above All-Clad D3 is the industry standard for clad cookware, regardless of the number of plies. You can find clad cookware that's thicker (Demeyere, Misen) and thinner (many less expensive brands). If you can handle heavier cookware, Demeyere Industry and Misen are both great choices. Anything thinner than D3 will sacrifice even heating and heat retention, so D3--and its best quality knockoffs, Tramontina Tri-Ply Clad and Cuisinart Multiclad Pro--are the thinnest clad cookware we recommend.
The exception, of course, is copper core, because copper heats more efficiently than aluminum. But if you stray from All-Clad Copper Core, it's hard to know how much copper a brand contains: because copper is expensive, some makers might use a thin layer of copper and thicker layers of steel or aluminum to compensate. So unless you know exactly how much copper a knockoff contains, it's probably best to go with a more transparent brand.
(By the way, buying any type of copper cookware can be a frustrating experience because there are so many configurations, and not all of them offer great performance. Some brands contain a good amount of copper, but most have a very thing layer of it, with some just being electroplated, which makes a pan look like copper without offering any of copper's excellent heating performance. Even All-Clad Copper Core, though it's excellent cookware, does not contain enough copper to compete with high-end copper brands like Mauviel and Falk.
We did a whole article about the types of copper cookware, how to pick the best type for you, and what to avoid (and why).
Weight
Weight goes along with thickness: in general, you want to buy the thickest, heaviest cookware you can comfortably handle. Thick, heavy cookware heats more evenly and hangs onto heat longer than its thinner, lighter counterparts.
You really have to consider how much weight you can handle, though. If cookware is too heavy, you won't enjoy using it.
All-Clad D3 and its knockoffs (e.g., Cuisinart Multiclad Pro and Tramontina Tri-Ply Clad) are right in the middle of the pack as far as weight: they're heavy enough to heat evenly and hold heat fairly well but not so heavy that they're hard to handle.
This middle-of-the-road design is what makes this cookware so great and so popular.
Heating Performance
Thickness and weight determine heating performance in clad cookware (and in most other types of cookware as well). In many of our articles and reviews, we talk in some detail about heating performance. But if cookware is thick enough and heavy enough, heating performance will be good.
All-Clad D3 is the standard, but it is also the lightest, thinnest you should go if you want good heating. If you go with a cheaper brand, stay away from anything lighter or thinner than D3. If you don't want to spend All-Clad prices, we recommend Cuisinart Multiclad Pro and Tramontina Tri-Ply Clad. Misen is also a good choice. Heritage Steel is another American-made brand that offers excellent quality and design, but the prices are similar to All-Clad prices.
Design
You want to look at design features such as handles, lids, and flat cooking surface. Are the handles comfortable and do they allow you to easily stabilize a full pot? Do the larger pieces have helper handles? Do the lids fit snugly? Does the skillet have a good amount of flat cooking surface?
Also consider whether you think the cookware i