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Copper Cookware Interior Linings

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There’s the ongoing debate (which I suspect will never die) about what interior is better for copper cookware: stainless vs tin vs nickel vs silver. American brand copper cookware is generally made either overseas (ironically) or by small boutique artisans these days, and anyone who cooks in copper has opinions about what they prefer their copper to be lined with. This is my take on it and why, but as always, it’s just my two cents!

First of all, I am completely in the camp that lining a non-ferrous metal (copper) with a ferrous metal (iron) goes against the point of using copper. Copper (and the tin bonded with it) has a thermal conductive speed of over 380W/m K, whereas stainless is around 25W/m K. Plus, if you want something made to last, and won’t slowly rust away, having metals that don’t contain iron is where to place your bets. Copper and bronze ewers used by the Egyptians thousands of years ago and stuck in Nile mud are still found in relatively the same shape and in good condition. Meanwhile, iron cooking pots in Viking digs that date back a mere 900 years are crumbled up and nearly gone to oxidation. Granted, stainless might not oxidize quite that fast (there’s no way to know yet, considering stainless steel has only been around for about 100 years) but you get the picture. I’m all about making something that should last for millennia. (why not?)

 

Anyway, regardless of my opinion, there are four generally used and/or viable metals for lining copper cookware.

The first is silver. This stuff is amazing. It’s the fastest (that means its thermal conductivity is superb, better than copper’s (406 W/m K), and is highly efficient in heating and safe for cooking food. It bonds molecularly with the copper, and lasts a long time if you use wooden or silicon utensils. There’s mainly one problem with silver, and that’s price. Since I know my cookware is already pretty pricey for some people, could you imagine if I coated it with silver? They’d be crazy awesome and super beautiful, but probably not practical. Bloomberg’s luxury list recently popped a silver saucepan, and it’s only you know…few thousand bucks.

The second interior option is nickel. In fact, many old and vintage pieces are wiped with or plated with nickel. Many times they can be refurbished with some good cleaning and a new coat of tin, and this is probably best due to the amount of nickel allergies out there. The nickel doesn’t leach into food the way, say, lead would, but it still would be touching the food and having a slight chemical reaction with it, so if you (or your dinner guests) had any type of nickel aversion, you probably don’t want to be cooking with it. And who wants to be on the line for that type of issue? No maker I know…

Then there’s stainless, which many people like because they say it’s easier to work with. I have yet to receive an answer on why exactly that is. If you’ve got a copper sauce pan that’s 2.5mm but lined with stainless, my guess is you’re still probably hand washing (correct me if I’m wrong and you have a magical dish soap for your washer that doesn’t result in pitting your copper?!) There is some ease in that stainless doesn’t scratch like tin, so you can scrape away at the stainless lining with wire and metal. Bear in mind that stainless is sticky (so clean up is harder) instead of non-stick like tin, and eventually it may pop apart due to the huge range in thermal coefficients between stainless and copper. Or your cookware isn’t pure copper, so it may stick to the stainless without much issue.

Clearly, I’m in love with tin lining. For me, molecularly, thermally, and purely – tin-lined copper takes the cake. Because of the electron exchange that happens when tin and copper are heated together (we’re talking over 500F), the molecular bond allows the thermal conductivity properties (ie: fast!) of the copper to transfer seamlessly through the crystal structure of the tin, allowing the copper to actually work the way it is supposed to when used as copper cookware. Plus, it’s non-stick and you need far lower temperatures to achieve the same thing, so it’s green/energy efficient plus always can be re-tinned over the decades, meaning it’s renewable and sustainable and won’t end up in a landfill. Tin has its downsides, of course. With daily use and proper care, it can slowly wear down. After about 12 -15 years your copper cookware may need re-tinning, which has to be done by hand.

 

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Copper Cookware: Vintage copper cookware seams

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COPPER COOKWARE SEAMS: HOW DO THEY DO THAT?

Before CNC machines and even hand-held lathes to make copper pots, we made ‘em out of copper sheets. This meant that we were stuck using small sheets sent over (and heavily taxed) from England (even though the copper itself was mined in America) and riveting, braising, seaming and pressing those sheets together in order to create nearly all copper cookware.

Everything that was made with copper was usually required to be waterproof. From boilers to cups to coffee pots to washpans – everything held some sort of liquid. By the 1700 – 1800’s, tin and coppersmiths knew to line the cooking wares with tin in order so the copper and heat wouldn’t combine for an icky combination.

But before anything could be tinned, or considered finished at all, the sheets of copper would need to be cut, fit and joined together with seams which were then either soldered or braised together.

Because there’s few places to list these seams, and there’s buzz about vintage copper cookware out there, I thought I’d put it out in writing in case anyone wants to delve into it. I’ve learned this at the tinsmith and coppersmith apprenticeship I’m so lucky to have at Backwoods Tin!

 

The Lap Seam

This very easy connection is simply when the very ends of the metal sheet (which you’re going to bend or curve) are clipped to your seam/burr allowances. The two metal ends are then placed next to one another, overlapping slightly, and then usually soldered together.

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Example of a lap seam exterior (on a tin mug).

The Crimp Seam

Make your hand into a C shape. Do it with the other hand. Now join the “C’s”. There’s your crimp seam. The copper sheet ends are bent into V shapes that fit together and then are pressed together. Another way to make a crimp seam along the base of a copper pot is to splay the bottom of the copper into a 90” burr, and fit a burred base around the burred bottom. Hammering down the exterior base burr over the top of the copper body burred base creates another version of the crimp seam.

(this can also become a double crimp seam if you take the finished seam and then push it up against the side of the vessel, or fold it over once more)

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Crimp Seam example along the base of a vintage sheet metal copper pot.

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Exterior View of a Crimp Seam on a Copper Pot

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The interior view of a crimp seam on copper cookware.

The Cramp Seam

A lot of very old vintage copper cookware has this particular method along the base. It has been called “dovetail seam” which is one way to describe it, as it certainly looks like splayed versions of the square dovetailing done on woodworking. However, in smith-talk, that’s a cramp seam. Those were insanely hard to do. Not only was the cutting very difficult, but also matching the copper together and then braising it to essentially melt the copper together, was incredibly painstaking. It’s one of the reasons they are rare – they were harder and more expensive to make so a plethora wasn’t made. They are beautiful…but tricky!

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Example of a Cramp Seam on a copper cookware base.

So there you are! Three kinds of seams, all of which can be found on American copper cookware made the old way – sometimes more than one is used, depending on the copper cookware made. Either way, they all helped make those canteens, cook pots and beer mugs waterproof, which was the end goal after all.

{If you want to purchase the modern versions of pure metal American copper cookware, I’d be thrilled to share my copper obsession!}