With Copper and Tin You Can Fuhgeddaboudit.
Tin, like copper, is many times more thermally efficient than stainless steel. That makes it a much better choice for lining copper pots and pans. Leaving an empty stainless-lined copper pot on heat will delaminate the lining (owing to vastly different expansion coefficients). It takes a long time, frankly a lot longer than it would take to damage a tin lining, but once your stainless lining delaminates, well, that pot, along with its copper, is ruined.
Likewise, the expansion coefficients of iron and the enamels that are often used to coat it are vastly different. Over time and repeated heating and cooling enamel will delaminate from iron, regardless of whether the pot was ever heated empty or not. Once that happens, that pot is a goner.
Above: We've heard of people who sandblast delaminated enamel linings to reveal perfectly good iron cooking surfaces - an inventive example of adaptive reuse.
Word to the wise: It's never a good idea to heat any lined pot empty. Naked iron and carbon steel are about the only cooking surfaces that can be safely preheated without risking your investment.
But, if you ever damage your Hammersmith tin-lined copper cookware you don't lose a thing. Just send it back to Brooklyn and we'll retin your pot to like-new. The first retinning is on us anyway, so you can enjoy all the advantages of the copper-tin team and never worry that your investment is at risk.
“Traditionally, of course, there is one ultimate kind of cookware, and it is made of copper which is becoming one of the rarer metals of the world. There is an enormous difference, however, in cooking pieces made of copper. There is the thin sort, which is of dubious value where good cooking is concerned. We've always considered one of the big ripoffs of our generation all that stainless steel merchandise with the copper-clad bottoms that was sold some years ago from coast to coast. And perhaps still is.
In any event, the real treasure is solid professional-weight copper lined with tin... a solid copper stock pot with tin lining, pounds heavy saucepans of various volumes. The cost is a king's ransom, but this is Tiffany-value stuff and will last well beyond the present lifetime of anyone reading this. The prices range from $20 for (a) charlotte mold to $185 for the stock pot, which includes an au gratin cover. The values will increase with time and in our books copper is a sound investment.”
Craig Claiborne, Craig Claiborne's Favorites from The New York Times, 1975, p. 73.
Note: $185 in 1975 equals $746.30 in 2010 adjusted for inflation. Have a look at our stock pot.
Above: The napkin drawing - isn't this how it always starts?
Above: Some say "Old Forge". We actually have one.
Above: Next step up from the Napkin Drawing.
The BrooklynCopperCookware.com test kitchen, aka Chez Mac.
Above: .090 (2.35mm), H02 (half-hard) 30K psi yield-strength pure copper sheet, as it comes to us. The new stuff is mined in Arizona and New Mexico, but what we get is normally between 25 – 40% recycled (still pure Cu).
Now, you've used stainless and have likely observed that it's pretty sticky stuff - that's why it gets lined with Teflon® and other polytetrafluoroethylene (PTFE) non-stick surfaces so often. A bare stainless steel surface grabs food like no other material; it's an alloy of steel, chromium, nickel and often other metals such as molybdeium and titanium and has a very complex molecular structure. It resists seasoning like it resists energy; you cannot season a stainless steel surface like you can iron or carbon steel, both of which are comparitively porous but molecularly well-ordered.
Pure tin, on the other hand, is as non-stick a cooking surface as can be found, short of taking your chances with PTFE (speaking of linings that should never be heated empty!). Food lifts off pure tin much as it does from well-seasoned steel, but tin does not require seasoning - its crystaline structure is already very smooth (i.e., molecularly simple and well-ordered).
Still, you can brown to your heart's content in tin - it's clingy in all the right ways. Perhaps you've noticed that on common PTFE surfaces water beads up - one of the reasons PTFE coatings don't brown well is that the water in food does not sheet, it beads. In fact, one of the ways to tell your PTFE coating has degraded is that water begins to sheet rather than bead.
Extending the geek moment, the theory goes something like this: The relative failure of PTFE to brown under heat indicates you have a very thin layer of water consistently between your food and the cooking surface. Normally heat would tend to push water further into food (searing 101: moist on the inside, crunchy on the outside), but when cooking on PTFE normal thermal effects on water are partly compromised owing to the free electrons fluorine (the F in PTFE, and also in its toxic byproduct, perfluorooctanoic acid, or PFOA) makes available for molecular bonding with the hydrogen in water. Heat apparently activates more of these free fluorine electrons, thus creating a greater hydrophilic (hydrogen-bonding/water-attracting) effect. Water is drawn to create a barrier layer between the pan surface and your food, which has to literally steam a good deal before it dries out enough to begin to brown.
While it may be problematic for quality cooking (decent fond anyone?), the hydrophilic quality of fluorine does keep the surface temperature of your PTFE lining closer to the boiling point of water, 100°C, which is below the level most authorities believe PTFE begins to outgas PFOA. So, by browning poorly PTFE keeps itself from hurting you.
There are, however, no such questions about tin. As we note all over this site, pure tin is molecularly and chemically inert - it does not react to variations in pH nor impart either flavor or volatile compounds to your food. It is not hydrophilic. It does very slowly oxidize (molecularly bond with oxygen) under heat, turning darker with use, and impart those oxides to your food, much as iron imparts oxides of iron when you cook in it. The net result of cooking in tin is you get a bit more tin in your diet, an essential nutrient for which, in the last century or so, most people suffer a deficiency (tin-lined copper pots and tinned cans started being usurped by iron, aluminum and enameled steel about 100 years ago. Today a so-called "enamel-lined" can is very likely lined with bisphenol A-based plastic).
The point here is less to provoke concern than to attempt an explanation for why tin-lined copper has endured across millenia and why it's so popular among serious cooks. Still, given what's already common knowledge about the persistance of petrochemicals in the environment and in our bodies, we're a little amazed that anyone would consciously choose to cook on plastic.
But, hey, that's just us. PTFE and PFOE may indeed be no problem, despite being completely synthetic, environmentally persistent and, now, ubiquitous. The people who make the stuff at DuPont are a lot smarter than we are, and they say there's nothing to worry about.
We agree; there's no reason to worry, because, you know, it's a done deal. We're not happy about having synthetic fluoropolymers sharing our cell space, so we're just taking a different tack with our cookware. The worst that could happen using our tin-lined copper? You get a little more of an essential nutrient (you probably lack), and your sauces go three-star.
The soffits and eaves? All copper.
No cookware material ... not aluminum, not iron, not ceramic, and certainly not stainless steel... conducts heat like copper.
The first thing you'll notice when using tin-lined copper cookware is how fast it heats up - in fact, you'll probably start turning down your heat as a matter of course. You just don't need a high-output burner when you use copper - the 3500°F at the tip of any propane or natural gas flame is plenty of heat. Whatever source of heat you use with copper cookware (except induction, which only works with ferrous metals) you can count on the energy going into the pot, rather than bouncing off the bottom and going up the outside while the metal figures out what to do with all those extra BTUs.
We've tried copper cookware with all the available linings. There are a few options (including silver - amazing stuff. Still playing with that idea...) but as a practical matter only two are readily available: tin and stainless steel.
“Copper is king here: It has nearly twice the thermal conductivity of aluminum... is five times more conductive than cast iron and 25 times more than stainless steel. Serious cooks love copper for this quality.”
Nina Shen Rastogi - Slate.com
Above: Untrimmed stock pot shell.
What holds true for electricity is also true for heat (for only slightly different reasons). Going geek for a moment here, but to give you an idea of the relative abilities of stainless steel and copper to pass energy through themselves: stainless steel's thermal conductive coefficient, or k , is 16 watts per meter (kelvin), or W/mK. Copper's k = 401 W/mK.
16 verses 401. Copper is 25 times more conductive than stainless steel. You can also read that as copper cookware using 25 times less energy to move the thermometer up a degree. Those high-output (i.e., energy wasting) burners? They came along in response to the use of high-resistance stainless steel cookware.
And yet lots of copper pots are lined with stainless steel in thicknesses between .5 and .75mm, just heavy enough to keep the lining from warping under heat. To get to the thermal efficiency of 2.5mm copper, stainless steel would have to be 25 times thinner than the copper outer layer – on a 2.5mm thick copper pot that would be .1mm; less than the thickness of a 6 mil plastic trash bag or heavy aluminum foil. Think about that. Your heat zips through a couple of millimeters of copper easy as you please, and then stops dead at a stainless steel liner to ooze up the sides for a while. Eventually the energy works its way into the stainless and then into the space within your pot, which is of course where you want it. With stainless steel you don't get what you want until a lot of BTUs have been squandered against the high resistance of the metal.
(And don't get me started on ceramic, a material with some organic currency in the cookware biz right now. Well, it is organic - clay comes straight out of the earth just like copper, and vitrious ceramic is chemically inert under high temperatures. Ceramic is so thermally inefficient, however, that it's most often used as an insulator; its conductivity coefficient 6.3 W/mK, 67 times less efficient than copper. One could say that as cookware ceramic is tailor-made for wasting energy).
Stainless steel dominates the world of cookware, from pots and pans to knives. Certain of its working properties are justly appreciated, mostly that it's stainless (read: mostly rust-free). In the case of knives the trade off for rustproofing is that stainless neither holds nor retakes an edge as readily as the other principle knife-making material, carbon steel. The purpose of a stainless knife - cutting - and how well it does that task is subordinated to how it shiny it stays.
Stainless steel is a very hard metal, and that hardness resists taking on a fine edge. That same resistance accounts for why the wires in your walls are not stainless steel - as tough and resilient as it may be, stainless is worthless for conducting electricity - too inflexible and resistant. The wires in your walls are very likely made of copper, which conducts electricity with very little resistance. In fact, copper has the highest electrical potential of all the non-noble metals. We're talking about cookware, however, and in cookware conduction in the name of the game.
Make no mistake, we respect stainless steel. For bike parts and sailing tackle, if it's not aluminum alloy or carbon fiber, stainless is what you want pretty much everywhere. The folks at Hammersmith have made a great many of the restoration parts for the High Line Elevated Park from stainless steel.
For cooking there are better, more efficient, more culinary, less industrialized choices, which is why we've gone with 100% tin-linings for our copper cookware.
In the history of cookery, copper and tin have been at the forefront of every major step forward, not only during the Copper Age but like when the great Auguste Escoffier discovered that tin linings for canned goods would prevent the French army from dropping in its boots from botulism and lead poisoning. He picked up that fact from a study of how his copper pots and pans were made. That little advance netted him the Legion d' Honneur, a place in history as the father of modern French technique (and as arguably the world's first celebrity chef), and may have something to do with the tradition of copper being known as the chef's "metal of honor".
The first metal age was the Copper Age, and some of the first metal tools were for cooking. The first metal alloys were of copper and tin, leading to the Bronze Age. Copper and tin have literally accompanied mankind on our cultural path, harmonizing each step of the way with human needs and with the environment. This is no less true today than it was 7500 years ago.
We're suckers for a good story.