Basics

How to tell nickel from stainless

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I speak from experience when I say that it can be hard to tell a nickel-lined copper pot from a steel-lined one.

I got into a heated argument on Chowhound over this. I insisted a particular pot of mine was lined with stainless steel but I was dead wrong: it was nickel. I was absolutely sure I was right because to my eye it looked just exactly, exactly like steel. I am embarrassed to have been so adamant when I was in the wrong, and I told myself I’d learn more about nickel and steel so that I could avoid this mistake in the future. (Reining in my ego is a separate challenge!)

One comforting realization is that at least I’m not alone: many people seem to make the same mistake. I’ve seen multiple eBay and Etsy item listings for copper pots described as tin- or steel-lined that I suspect are nickel-lined. I don’t think it’s necessarily malicious on the part of the seller, because they can be difficult to distinguish from each other, and ultimately the pots will perform similarly.

But it’s good to know which lining you have because nickel needs to be treated more like tin — no metal utensils, no hard scrubbing — while steel can withstand rougher handling. I’d like to share with you what I’ve learned in hopes that it will help you to be a more informed buyer.

Stainless steel as a lining for copper pots

Stainless steel is an alloy of iron, chrome, and nickel. Each of these component metals bonds differently to copper — nickel rather well, but iron and chrome not very easily. This makes it difficult to get steel to adhere to copper without some kind of intervention.

In the early 1970s, US manufacturers such as All-Clad were bringing sophisticated multi-ply steel pans to market using advanced techniques to bond, shape, and finish clad cookware, and French manufacturers had to compete. In the 1970s, the Belgian cookware firm Falk Culinair developed and patented a process to bond sheets of copper and steel into “copper bimetal”: 2.3mm of copper and .2mm of steel for a total thickness of 2.5mm. Falk found a German sheet metal supplier to mass-produce bimetal sheets and in 1983 released a line of steel-lined copper cookware.

Others quickly followed suit. In 1989, Mauviel began manufacturing Cuprinox, their own line of steel-lined pans. (They used the Cuprinox name until circa 2007 when they switched to the M’150/ M’250 nomenclature.) Other French manufacturers including Atelier du Cuivre, Havard, and De Buyer began making stainless-steel lined pans in the 1980s and continue to this day.

Stainless steel linings for pots come in brushed, mirror, or matte finishes depending on the copper bimetal stock and how the pan interior is polished at the factory. Steel withstands high cooking temperatures (Mauviel rates its steel-lined pans to 500°F/260°C) and its hardness means that even the .2mm in a typical pan lining will tolerate metal cooking utensils and hard scrubbing with no more than a few surface scratches.

Nickel as a lining for copper pots

Like tin (and unlike steel), a nickel lining is applied to the pot after it’s been formed from a pure copper sheet. Nickel can be arc sprayed or plated onto copper, and depending on how it was applied and polished, it can have a brushed, mirror, or matte finish just like a steel lining.

According to copper cookware dealer TJFRANCE, nickel-lined copper pots entered the French market in the early 1980s, hailed as the great replacement for tin. My mother purchased a set of nickel-lined pans at Dehillerin in Paris in the early 1980s, and I’ve read anecdotally of others also buying new nickel-lined pans in that timeframe.

I know of two lines of French nickel-lined copper: Mauviel’s “Cupronil” and L. Lecellier’s “Cunilec.” Both of these lines were sold at Dehillerin in Paris. Bourgeat made a line of nickel-lined pots and there are likely others as well, and I would welcome more information.

As a lining for a copper pan, nickel conveys some of the desirable qualities of both steel and tin. Like steel, nickel can withstand cooking temperatures above 450°F/232°C that threaten to soften or melt a tin lining. Pure nickel conducts heat slightly better than pure tin and much better than stainless steel, so it helps support the thermal performance of the copper pan. And like tin, nickel releases food well, much more easily than steel.

In terms of physical resilience, nickel is hard like steel, but the problem is that there’s just not that much of it on the pan. A sprayed or plated nickel lining is approximately 15 microns thick — that’s .015mm, much thinner than the 200 micron (.2mm) steel layer in an average copper bimetal pot, and even thinner than a hand-wiped tin lining. Stainless steel is tough but not impervious — look closely at a well-used stainless steel pan and you’ll see many surface scratches. A nickel lining handled as roughly could pick up scratches deep enough to penetrate through to the copper. For this reason, I suggest you think of nickel as “high-heat tin” and give it the same treatment: hand-washing, no harsh scrubbing, no metal utensils.

TJFRANCE has observed that unused nickel-lined pots seem to degrade over a period of years — that is, that the act of cooking and cleaning the nickel appears to help maintain it, and that without this attention, the lining may develop pits or other defects. I haven’t confirmed this with my own experience but I trust TJ’s advice here. If you come across a set of vintage nickel-lined pots, take a close look at the condition of the lining and be prepared to re-line the pots if needed.

Shopping advice

It’s within the realm of possibility that you’ll spot a vintage copper pan with a silvery metal interior that’s described as stainless steel or tin but that actually could be nickel. You could examine the pan if you had it in front of you, but if it’s on eBay or Etsy you may need to work from photos and ask the seller some questions. Here are some suggestions that may help you during this process.


Hand-applied vs. machine-applied linings

You’d think it would be easy to tell a hand-wiped tin lining from a machine-applied steel or nickel lining, but in practice — and especially in photos — it’s not always immediately obvious. An older nickel-lined pot of mine that you’ll see below has a mellowed matte texture similar to a used tin lining, and an inexperienced seller may not know the difference.

But there is one reliable telltale of a hand-applied lining: the rim. Look at the rim very closely, or ask the seller to take a photo or look on your behalf. Is there any silver metal on the flat surface?

  • If the rim is solid copper all the way around, it’s most likely a machine-applied lining, either nickel or steel.
  • If there is any silvery metal on the rim surface, it’s most likely a hand-applied lining, with some tin that has spread from the interior onto the rim during the process.
Cupretam, Cuprinox, and Cupronil
Left: A clean rim likely means steel or nickel. Right: Silvery metal on the rim likely means tin.

Copper thickness

A good general rule is that a pan thicker than 2.5mm or so can’t be lined with stainless steel. It’s hard to prove that a thicker steel-lined pot doesn’t exist, of course, but I’m not aware of a tested and nickel-negative example thicker than 2.5mm. (I thought I had one, hence my spirited argument on Chowhound, but I was wrong — if you have one, please test it and share the results!) If you have a pot that is thicker than 2.5mm with a non-tin lining, there are a few possibilities as to what it could be, in order of descending likelihood: nickel-lined (most likely); aluminum-lined (L. Lecellier’s Cuivralec, or an aluminum pan plated with a thin shell of copper); one of GAOR’s nested copper-steel pans; or silver-lined.


Examples

I have three pots that I believe can serve as useful examples to show the similarities and differences between steel and nickel.

The 26cm sauté pan on the left is a stainless steel lined Cuprinox extra-fort (high thickness) pot at 2.5mm thickness. The other two are nickel-lined Cupronil made sometime between 1960 and 1990: the 28cm saucepan on the right is new old stock in factory-fresh condition, so I call it “new,” while the 28cm stewpot towards the back has been used and scrubbed to soften the lining’s factory finish, so I call it “old.” They are both 3.8mm thick and are absolute units.

How to tell nickel from stainless
Front left: Cuprinox, stainless steel; back center: “Old” Cupronil, nickel; front right, “New” Cupronil, nickel.

Here are some detail photos of each pan. Note how similar the nickel and steel look; many nickel-lined pans are mistakenly listed as stainless steel on eBay and Etsy because even well-meaning sellers can’t tell the difference. I believe these three were all made by Mauviel but none of them is stamped “Cupronil” or “Cuprinox.”

The interior polishes look really similar to my eye. Many Cuprinox and Cupronil pans appear to have received a factory polish to the lining that produces a concentric ring pattern. This pattern persists in a stainless pan because of the hardness of the steel. By comparison, the nickel lining can be scrubbed away, which is why it’s useful to have the “new” and “old” examples to illustrate this.

The photos below show the sharp-edged “new” Cupronil lining, factory-fresh with a brushed finish, and the “old” Cupronil pot that has been used and thoroughly scrubbed over its lifetime. The remnants of the “old” Cupronil’s original brushed finish are faintly visible, most clearly at the top of the sidewall seems not to have been scrubbed like the basin.


Tone

While stainless steel and nickel are both silvery metals, there is a subtle difference in the tone of each: stainless steel has a cool bluish tone to it, while nickel looks warmer by comparison. It’s hard to see this on an individual pan, however, particularly in photographs. If you’re looking at a pan online, see if the seller will take a photo of it with a known steel-lined pan.

I’ve used two comparison pans in my photos below: my known Cuprinox steel-lined pan and a Demeyere Atlantis skillet with an outer layer of 18/10 stainless steel. To my eye, the two finishes have a different color cast. Nickel is sometimes described as “yellower” than steel, and it shows up in these side-by-side comparisons. It’s more subtle between the Cuprinox pan and the “old” Cupronil, whose finish has been dulled with scrubbing, but the yellowish cast is there, particularly right next to the bright Demeyere steel.


A tone example

This photo below from an eBay listing illustrates the visible difference in tone. Look at all these pans — does one of them stand out a little?

How to tell nickel from stainless

The seller says that the sauté pan in the upper left corner is 2.5mm thick while the rest of the saucepan set is 3mm. Those thicknesses as well as the different tone of the color of the lining of the sauté leads me to believe that the sauté is steel-lined while the rest of the saucepans are nickeled.


Pearliness

The photos above also show a distinct quality I perceive in a nickel lining: once used and scrubbed, the nickel takes on a uniform soft matte texture I call “pearliness.” I suspect this is because nickel, despite its hardness, can be scrubbed away with cleaning; I see the same pearly look on aluminum (a very soft metal) and on stainless steel that has been thoroughly and chaotically scrubbed, like my own stainless steel sink.

Pearliness cam be an indicator of nickel but it’s not infallible, as bead-blasted stainless steel finish can look very similar. Compare the three photos below: a nickel surface; a bead-blasted steel surface on the underside of a copper lid; and for context, a Mauviel bead-blasted oval pan. The difference to my eye is that the bead-blasted steel has a sparkly metallic look while the nickel is has a flat gleam without as much sparkle.


Magnetism

There’s a lot of disagreement about whether you can use a magnet to tell if a lining is stainless steel or nickel. According to my testing with these pans, you can’t — they’re all similarly magnetic. I found that a small magnet stayed put on all interior pan surfaces, with the exception of the rivets; the rivets of the “new” Cupronil were strongly magnetic, while the rivets on the Cuprinox and “old” Cupronil were not magnetic at all. (The iron handles are of course highly magnetic and I was careful not to measure that by mistake.)


Nickel testing

The best way to tell nickel from stainless is to use a chemical nickel detection solution. I ordered this test kit from Amazon for about US$35. An online seller may be unwilling to go through this expense and process for you, but it’s the only incontrovertible test for nickel.

To test the surface, wet the tip of the cotton swab and rub it against the metal for 15-30 seconds. The solution is colorless, but if there is nickel detected, the chemical will turn pink. In practice it wasn’t a dramatic change but there was discernible pink on the swabs from the two Cupronil pans while the Cuprinox swab stayed clear.


Considering nickel

Should you buy and use a nickel-lined pan? As long as you don’t have anyone with a nickel allergy in your household, sure. I offer the following comparison of tin, nickel, and steel as the lining for copper pans in the hope that it helps you think it through.

  • Tin, the original lining for copper cookware, is compatible with a wide range of copper thicknesses, provides great thermal conductivity, and is low-stick with food. However, tin melts at 450°F/232°C and can soften during high-heat cooking, and is a soft metal that can be scraped away with metal utensils or heavy scrubbing. Fortunately, a tin lining can be renewed indefinitely over the lifetime of the copper pan.
  • Nickel improves upon tin’s heat tolerance and resilience and offers similar thermal and low-stick performance. However, the lining can be quite thin, and nickel-lined pots left unused for years should be examined closely to see if the lining has degraded. Nickel can be scratched or rubbed away with metal utensils or heavy scouring, and must be renewed by a metal plating shop with thermal spraying or electroplating facilities. (Alternatively, a coppersmith can re-line the pan with tin.)
  • Copper-steel bimetal provides the same high-heat tolerance as nickel with the resilience to withstand metal utensils and heavy scouring. Unfortunately, bimetal pans are limited to 2.5mm of total pan thickness (ironically, preventing steel’s poor conductivity from interfering too much with copper’s performance). However, food tends to stick to stainless steel much more than to tin or nickel, and if the steel lining is damaged, it cannot be repaired and the pan must be discarded.

Vintage nickel-lined copper pans can be tremendous values. They can be quite thick — up to 3.5mm or more — and the linings perform beautifully for cooking. If you are considering purchasing one, the most important consideration should be the integrity of the nickel lining, as it may be difficult to find a re-plating or spraying service. That said, if re-nickeling a worn-through vintage lining is not a possibility for you, you can have the pan re-lined with tin and enjoy the pan for several more decades.


Corrections

  • TJFRANCE offered some information about nickel’s use in the industry that I’ve incorporated into the narrative. He also has observed that nickel linings seem to degrade over time, even without use, so I’ve included that caveat.
  • Erik Undiks at Rocky Mountain Retinning suggests that French manufacturers stopped making nickel-lined pans circa 1994, when the EU began to regulate the amount of nickel in consumer products due to skin contact allergy. I think this sounds reasonable and I’ve amended the text accordingly.
  • I had originally ended this article with the question of why nickel is no longer used in French cookware, but I believe the EU regulation answers that question. Instead, I adjusted the conclusion section to compare the benefits of tin, nickel, and steel.
  • I’d speculated that Mauviel’s suggested temperature limit for its steel-lined pans — 500°F — was to prevent possible delamination. Harestew suggests that it’s more likely to prevent bluing and damage from overheating, and TJFRANCE echoes this.
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3 Comments

  1. Great article on Stainless v Nickel!
    Yes, at Normandy Kitchen we test chemically for nickel if we are not sure whether it is nickel or stainless steel. I personally love nickel lined pans, they conduct heat well and are more robust than tin but not as hard wearing as stainless steel so they are a great compromise. I have a 20 cm Chomette Favor saute I use all the time.
    Keep up the good work!!

    1. I’m so glad to hear that you test your pieces for nickel. It underscores that you’re a responsible seller. Many sellers don’t and I wish they would because nickel does have different care requirements than stainless. Buyers should know this so that they don’t use abrasive cleaners on the lining. Other than that, cook away! 🙂

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