Antique Copper Pans

[bleudauvergne]

We used to have this diction exercise -

"Are you copper-bottoming 'em my man?

No I'm aluminum-ing 'em 'mum! "

This was something that we repeated incessantly before going on stage - Um, I'm not sure why. Anyway, this phrase is coming up again as I consider whether to cook in a roughly 100 year old tourtiere I picked up at the flea market last week.

It's real pretty. It's made of copper and the inside is lined with some kind of silver looking metal but I'm not sure what kind. This pan is from the late 1800s.

What are 100 year old copper pots lined with and can I use it to prepare a tourte without endangering my loved ones lives? It looks similar to the stuff that my contemporary copper pans are lined with - not sure though. Any experts out there?

[Mayhaw Man]

Well, how about an inexpert guess-

Tin

Aluminium and stainless didn't exist 100 years ago (I don't think so, anyway-at least I don't believe that they were being used in commercial products), so I'm thinking it's probably tin.

[bleudauvergne]

So if I lined it with parchment paper I won't die of tin poisoning?

[winesonoma]

Lined with tin, watch the heat as it will melt at high temp. 231.93 °C (449.47 °F)

Edited November 4, 2005 by winesonoma (log)

[JayBassin]

Some good cooking stores will arrange to have the pan re-tinned. La Cuisine in Alexandria, VA, and I think most of the Sur La Table stores will do it.

[jsolomon]

Pure elemental sodium. Don't flush it down your toilet with the children watching, or you'll never keep them from being mad scientists when they grow up.

[andiesenji]

Most copper pans of earlier times were lined with tin. Years ago you could buy re-tinning kits which contained stuff that was like tin solder which you melted in the pan, then swirled it around to coat the inside. You could not use the pans over very high heat and utensils, even wooden ones, would eventually wear away the lining.

However, beginning in about 1894, small copper skillets were made by a few makers and were lined with stirling silver and highly polished.

These were made specifically for gently cooking mushrooms at the table because at the time it was believed that the silver would instantly turn black if a poisonous mushroom was placed in the pan.

They are very rare.

However, occasionally one of these appears at an auction, sometimes at yard sales, unknown because the interior is black because the silver has tarnished. One sold on ebay a couple of years ago for big bucks, the name stamped on the underside of the handle was "Rothschild" - unknown if this was the maker or the owner.

Edited November 4, 2005 by andiesenji (log)

[slkinsey]

So if I lined it with parchment paper I won't die of tin poisoning? 

Make sure the copper isn't showing through the tin lining. Copper is poisonous.

[jsolomon]

On a more serious side, and complementary to slk's post, high acid foods are not compatible with tin, either.

Tin is not quite as reactive as aluminum, nor iron (think cast iron), but general care should be taken when cooking acidic foods in tin, as well.

[Carolyn Tillie]

Copper is poisonous.

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In what context - and how much? I'm sure EVERYTHING is poisonous to some degree, but as a jeweler, I have been filing and sanding and inhaling copper for 20 years and have never heard this before...

[jsolomon]

Copper is poisonous.

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In what context - and how much? I'm sure EVERYTHING is poisonous to some degree, but as a jeweler, I have been filing and sanding and inhaling copper for 20 years and have never heard this before...

←

Copper ions tend to precipitate your proteins out of solution, inside your cells. This is incompatible with life.

Ingested copper is not very good for you.

But don't take my word for it. Take the FDA's.

Edit to add the good news is copper chloride (what you're likely to form in your digestive system by ingesting metallic copper) is much less poisonous than other compounds of copper.

Edited November 4, 2005 by jsolomon (log)

[ludja]

Here is some other information that looks reliable: click

The full article discusses potential health issues in more detail.

The Dietary Reference Intake (DRI) guidelines, set in 2001 by the U.S. Food and Nutrition Board of the National Academies Institute of Medicine, set both the recommended dietary allowances (RDA) and the upper intake levels for copper. The group’s intake recommendation is 0.9 milligram of copper a day for adults, more for lactating women (1.3 milligrams) and less for children (0.34 milligrams for children up to three and 0.44 milligrams for children between four and eight years). The upper limit is 10 milligrams per day for healthy adults. Since the body does not synthesize copper, this essential level of copper must come from nutrition.

[slkinsey]

Copper is poisonous.

In what context - and how much? I'm sure EVERYTHING is poisonous to some degree, but as a jeweler, I have been filing and sanding and inhaling copper for 20 years and have never heard this before...

What they said above.

Copper is one of those things that is essential is small amounts and poisonous in larger amounts. Copper poisoning is usually an acute condition, but is is possible that it can build up and have a cumulative effect over time. So, for example, cooking tomato sauce in an unlined copper pan might not make you sick. But eating that tomato sauce 5 times a week for six months would be a very bad idea. This is all the more true because soluble copper compounds are the ones that pose the greatest risk to human health.

If you think you're ingesting a fair amount of copper (I don't know how often you work with copper or how much of it you might ingest on a regular basis), I'd recommend doing something to minimize your exposure (gloves and a mask, for example).

[Eden]

I read somewhere (maybe in Patricia Wells' Food Lover's Guide to Paris?) that you can get copper pans retinned in Paris, which is probably a bit closer to you than VA

I would worry a little bit that it might be an alloy rather than pure tin, in which case you would have to question what it's been mixed with - our ancesters were not so afraid of lead as we might like...

[rancho_gordo]

How much copper do you take in by cooking food in a copper pot?

How many dishes don't contain acid? Just a few in my book!

What about carnitas which are traditionally fried in an unlined copper vessel?

I have a copper pot from France that needs to be retinned (after 3 uses!) but I can't see why I should bother. I just don't use it.

[jsolomon]

How much copper do you take in by cooking food in a copper pot?

How many dishes don't contain acid? Just a few in my book!

What about carnitas which are traditionally fried in an unlined copper vessel?

I have a copper pot from France that needs to be retinned (after 3 uses!) but I can't see why I should bother. I just don't use it.

←

One thing to keep in mind, r_g is that the acid scale, from 1-14 (aka the pH scale) is a logarithmic scale, not linear. So, a drop in pH from 5 to 4 indicates a 10-fold change in acid activity. There are a lot of things in the 5 to 4 range. For pan uses of less than 30 minutes, I would not fear this very much (keep in mind, I'm giving my feelings here with no real evidence to back it up. YMMV) For high acid foods, in the 4-3.5 range, 5 minutes in the pan. For even higher acid foods, I wouldn't use the pan at all.

Also, keep in mind, acid strength changes as temperature changes. That's just how the thermodynamics work. So low acid, high heat, long temperature, can give you the same results, copper corrosion-wise.

[Carolyn Tillie]

I guess that's the rub -- like Rancho Gordo said, how much copper does one consume by cooking in a copper pot? I imagine it would be more over extended periods of time, but I'm sure that I have consumed more copper as a metalsmith than an average person would by using a copper pot in their kitchen.

[slkinsey]

What about carnitas which are traditionally fried in an unlined copper vessel?

Certain things, like high fat/neutral pH carnitas or melted sugar, etc. seem to be okay. . . which is to say that they seem like cooking tasks that do not encourage copper to dissolve into the food.

That said, there are a lot of things that are "traditionally" cooked in ways that are poisonous (e.g., cooked in lead-glazed pottery, etc.).

I have a copper pot from France that needs to be retinned (after 3 uses!) but I can't see why I should bother. I just don't use it.

This is one of the reasons I always recommend that people buy stainless-lined heavy copper instead of tin-lined. You have to baby tin-lined copper substantially more than even nonstick. No high heat, only soft (wood or thermal plastic) utensils, no scrubbing of any kind, etc. If your pan needs to be retinned after only three uses, it's likely that you either didn't use it gently enough or the pan wasn't tinned particularly well to begin with. It's also the case that a lot of what seems like "bargain priced French copper" is actually not made to be cooked with at all, but is meant for table-side presentation and service (e.g., Mauviel's table service line).

Of course, if you don't use it -- problem solved!

. . . I'm sure that I have consumed more copper as a metalsmith than an average person would by using a copper pot in their kitchen.

It's hard to say whether or not that is true. There are several things to consider: You're probably not getting all that much copper into your body via absorption into the skin simply by handling copper with some frequency. So what we're talking about in your case is how much copper you have potentially inhaled in dust form from sanding copper (or perhaps in vapor form?). Unless you're leaving visible drifts of copper dust on your work surface (as, for example, a sculptor who works large pieces of copper might), and unless you're getting this exposure on a daily basis, it's unlikely that you're ingesting a great deal of copper. More than a "regular person," sure. . . but maybe not meaningfully more. From what I have read, it seems highly unlikely that you are being exposed to a copper particulate level in the air (~5,000 ng/m^3) that would make it likely that you would suffer from the various health risks associated with such exposure (metal fever, atrophic changes to nasal mucous membranes, various lung ailments, etc.).

Then there is also the issue of the form of the copper. As I mentioned upthread, the soluble copper compounds (i.e., those that are likely to get into your food from cooking in a copper pan) have a greater impact on human health compared to the forms in the copper dust you might be getting from your work. So, I would guess that cooking in copper on a regular basis puts more copper and more of the worst forms of copper into the human body than working with copper jewelry. Of course, I don't fully appreciate the kind or magnitude of your work. If you're regularly working in an environment where copper dust and vapors are filling the air, you might consider protecting yourself.

[NB. When I say "cooking in copper" here, we're talking about cooking in unlined copper, or in copper cooking vessels in which the lining has substantially failed. I cook in copper all the time, but in stainless lined copper where the food never contacts the copper.]

[jayt90]

This thread has produced a mine field of information and misinformation. The original vessel described by bleu may well be safe because there is no note about copper showing through, and no apparent need to re-tin. Some of us think that tin is toxic, but it is still allowed for sale as a copper lining, after testing by my government.

When the tin begins to wear through (my French pans lasted several years) I was still able to use them for non acidic foods, without getting sick. The usuual warnings at the time (70''s) were to avoid a pan (or food) with blue/green colouring, a sign of cupric sulphate. Never got sick, if I avoided this.

I wish I could find 100 year old copper pans in my neighborhood!

[slkinsey]

The original vessel described by bleu may well be safe because there is no note about copper showing through, and no apparent need to re-tin. Some of us think that tin is toxic, but it is still allowed for sale as a copper lining, after testing by my government.

I agree that a tin lining should be safe. The discussion about copper and safety for cooking evolved out of a discussion on "what if" the lining was failing.

When the tin begins to wear through (my French pans lasted several years) I was still able to use them for non acidic foods, without getting sick.

Hey, knock yourself out. It's your own body and you can take your own risks. I will simply point out, however, that it's possible to ingest too much copper (and lead, etc.) without immediately getting "sick" from it. Especially if you're only using it maybe a few times a month. I cook with my copper cookware on a daily basis, and personally I wouldn't use a copper pan for "regular cooking" if the tin lining had failed. I'd get it re-tinned. Plenty of people eat food that's been cooked in lead-glazed pottery every so often, or drink hard booze that's been stored in a lead crystal decanter for years and don't "get sick" every time they do it. . . but that doesn't mean it's not a bad idea.

[jsolomon]

I must admit, part of my suggestions of caution are due to me being the guy who had to tell a mother that her daughter was exhibiting the signs of chronic heavy metal poisoning... along with 30 of her classmates. Then, I had to continue working with the mother for the next two years after that. It was a very grim situation for a long long period of time.

The good news is that the daughter is fine now. The bad news is that some of her former classmates are not. Chronic metal poisoning is a shitty way to go, so I urge all people caution when using reactive cookware.

[jayt90]

Bare copper vessels are used for high temperature sweet confections, and for beating egg whites.

The real culprits are cupric sulphate (easy to spot), lead (not so easy) and aluminum (jury still out on this one.)

[andiesenji]

I use unlined copper pots for cooking sugar and for low-acid fruit preserves. As noted above, minute amounts of copper are okay and even beneficial.

Consider that the reason egg whites beat up to more volume in unlined copper bowls, with each bubble wall stronger because during the beating the whites pick up copper molecules. As I recall, this was described in detail by McGee in his first book.

I have an ancient poaching pan (for eggs) with the large dimples in the bottom. It was tinned at one time but much of the tinning has worn away but I still use it because I use only water without the traditional addition of vinegar to poach a bunch of eggs. Incidentally, the depressions in the bottom of the pan were not to hold the eggs, one was supposed to swirl the water, with the handle of a wooden spoon, to form a localized vortex right above the depression and the egg was then slipped into the center of the vortex.

I have seen these often in antique stores and some of the explanations given by sales people are comical. They have no idea how these were supposed to be used.

It is indeed possible to get too much copper into foods if the foods are acidic. Oddly, if a person is taking iron supplements, the copper will not be absorbed. This was discovered accidentally when cattle fed on highly alkaline soil in ancient sea beds that also have high iron content, exhibited copper deficiency and were not gaining weight correctly.

I agree with jsolomon.

Heavy metal poisoning is nothing to brush off. I have worked for an orthopedic surgeon for many years and have taken x-rays and found lead lines near the ends of long bones in the legs and arms from people using vessels for foods that were made in Mexico with lead-based glazes.

The chelation treatment is not fun. We also found similar bone deposits in stained glass artists who were using lead solder (which produces fumes) without any protection. Occasional exposure is not a problem, it is when one is exposed daily over long periods. Children are much more susceptible because body mass counts in how much can be unsafe.

Heavy metal poisioning is not immediately symptomatic and we only found these cases because these individuals complained of joint pain unrelated to this. When other family members were x-rayed, we found they all had the same findings and all had to be treated. That is why many of these things in stores have a sticker that says "For Decorative Use Only" but when you buy them in Mexico, or at yard sales, these stickers are missing.

There are test kits for lead available to check your pottery.

On the other hand, I don't worry about glassware containing lead used only for serving food. I did engraving in leaded crystal for many years and wore a respirator because of the glass dust, not the lead.

Several experiments have been done with various liquids, wine, liquor, beer, etc., leaving it in the vessels for varying periods of time. I wouldn't STORE wine or food in lead crystal but using a bowl or carafe for serving, or using wine glasses does not consitute a problem, the liquid is not in contact long enough to leach out an appreciable amount of lead. It took a minimum of 36 hours to show any leaching at all. High acid solutions took a minimum of 3 hours to show any leaching at all.

[andiesenji]

Bare copper vessels are used for high temperature sweet confections, and for beating egg whites.

The real culprits are cupric sulphate (easy to spot), lead (not so easy) and aluminum (jury still out on this one.)

←

Copper vessels should be cleaned well before using. If they have a gray or gray blue film or tarnish on the interior, scrub it off before cooking anything in it.

Half a lemon dipped in salt and scrubbed over the surface will take off all this stuff right down to the bare metal.

[markovitch]

when i got ancient family copper retinned, the man who did it told me the tinning was so old that it had a high lead content.

i don't know how old they are, or how much lead we're talking about, but since he re-tins things, i thought him a trustworthy enough source to mention here.