For my birthday I received this handsome copper paila from my step daughters and their husbands (Thank you again, M, M, J & N.). Aside from its beauty, I knew that copper was one of the best cookware materials because of its rapid and even heating. But I also knew there were some problems in cooking in copper… but exactly what they were, I didn’t know.
As I began to search the internet, I quickly discovered that most copper cookware is coated with another metal because copper oxidizes when in contact with acids, creating the greenish patina seen on old copper, bronze and brass. This patina, called verdigris, is toxic and can cause gastrointestinal problems if ingested.
Traditionally copper was lined with a thin coating of tin, but tin scratches and will wear away in time. Tin also melts at only 425° F, a temperature easily reached in cooking. Nickel is also used as a lining, but the most common lining today is stainless steel.
My paila seems to be unlined. There is no obvious lining, the color is the same inside and out, and ArteCobre, the major seller of Chilean copper cookware (and presumably of mine), makes no mention of lining. Not a good sign, as one of the first copper cookware sites I encountered had this warning:
Source: The Copper Shop
The information sheet which came with my paila said the following:
Cooking with pots or utensils of copper
Copper has been commonly used in pots and kitchen utensils, it is very easy to work but it has its problems. What are the advantages and disadvantages of cooking in copper pots and utensils? (All translations mine unless otherwise noted.)
The advantages listed were: copper’s even heating and rapid conductivity of heat, the reduced tendency of food to stick because of the uniform temperature of the cooking surface, copper’s antibacterial properties, that vegetables like asparagus and artichokes cooked in copper retain their bright green color, and that jams and jellies cooked in copper are delicious and maintain a brilliant color. The final advantage is that
Poisoning from cooking in copper does not occur easily [La intoxicación cocinando con cobre es muy difícil] because the pot or utensil lets us know we should not use it through its green patina, and in addition, food cooked in it would have a strong flavor that would keep us from eating it. By contrast, we are being poisoned slowly without realizing it from tasteless traces of lead or asbestos in foods cooked in utensils of aluminum. We only have to keep copper utensils clean and unstained [to avoid problems].
When I searched the internet for the wording of ArteCoblre’s information sheet, I found it at En Buenas Manos, a site providing information on “Beauty, Ecology, Illness, Esoterica, Pets, Nutrition, Recipies, Reflections, Therapies, and Healthy Life.” The author was Josep Vicent Arnau, Naturopath and Acupuncturist.
There is a certain attractive logic to the idea that cooking in unlined copper is safe if you keep the copper clean and don’t eat anything cooked in it that tastes bad. And the articles I read on En Buenas Manos’ web site were sane, reasonable and not just marketing quackery, but Mr. Arnau’s credentials didn’t instill a great deal of confidence. (See Wikipedia’s article on Naturopathy and judge for yourself.)
Surely there is more authoritative advice.
And, of course, there is. I. Herbert Scheinberg, M.D., (1920-2009) professor of medicine at the Albert Einstein College of Medicine, was one of the nation’s experts on copper toxicity and Wilson’s disease, a genetic disorder causing the toxic accumulation of dietary copper in the liver, brain and other organs. According to one of the best articles I found, “The Importance of Copper Cookware for Cooking” from the site Retinning and Copper Care:
[Dr. Scheinberg] contends that unless the copper has oxidized extensively enough to produce the green-blue copper salts commonly known as "verdigris," and/or highly acidic foods are to be cooked in the pot [with scratched or worn lining], use of the vessel is not dangerous. If acidic foods come in contact with the copper, they'll dissolve and absorb the copper salts, which are toxic. If the salts are present, the pot should be scoured.
[He says ] "Yes, people can get gastrointestinal upsets. But contrary to popular belief it's not fatal."
The US Food and Drug Administration also has something to say about cooking in unlined copper pans:
John Thomas, of the division of regulatory guidance at the FDA’s Center for Food Safety and Applied Nutrition says that the agency cautions against using unlined copper for general cooking because the metal is relatively easily dissolved by some foods with which it comes in contact and, in sufficient quantities, can cause nausea, vomiting and diarrhea.
At this point it is obvious that my paila is not going to be my everyday pot. Egg whites and whipped cream are said to have more volume when beaten in unlined copper bowls, but what can be safely cooked in unlined pans?
Unlined copper vessels are produced especially for making sugar syrups and candies:
A sugar pot or sugar boiler is an unlined copper pan that is used, primarily by pastry chefs, to make sugar syrups. Because copper is so responsive to the heat, the pan gives the chef instant control as he or she boils the syrup to just the right temperature.
The acidity of the unlined copper causes some of the sugar to "invert," or split into glucose and fructose, which helps resist the sugar's tendency to recrystallize. The pans are also unlined because a traditional tin lining would come too close to melting temperatures in some cases….
They are also used to make jams and jellies, as in the Mauviel jam pan below, where it seems that the high sugar content offers some protection against the acids contained in the fruit… how and why, I could not discover.
And they are used for making polenta:
What they are clearly not used for is cooking acidic foods; no tomato sauce, meats braised in wine, or sausages with sauerkraut. But it seems to me that, if used with caution, and cooked in sparkling clean pans, foods that are low in acid should be safe. (But note I am an anthropologist, not a chemist, toxicologist, MD or anything close to being pertinent to this issue… this is not a recommendation for others.)
So what are low acid or non acidic foods? Here are some examples of foods that occur frequently in my cooking (For reference pH 7.0 is neutral; above 7.0 is alkaline; and below 7.0 is acidic; orange juice is 3.3 – 4.2)
It looks like green olives and tomatoes will definitely be excluded from my piala. Wine too, with an average pH of 3.3 to 3.7. But most everything else looks OK, especially if the bulk of a dish is a food that is close to neutral, like rice.
What did I cook? Paella.
Here’s my paella recipe. Average pH of ingredients: around 6.0 – 6.2. Serves 4.
Olive oil as needed
1 medium onion, chopped
1 - 2 cloves garlic, minced
½ green bell pepper
½ red bell pepper
3 chicken thighs, boned (bones reserved)
2 smoked sausages, 4-5” long
2 lbs. mussels
1 lb.clams (mine were very small, more ornamental than substantive)
1 ½ cups short grain rice
Thyme, paprika (AKA ají de color), saffron (if you have it, I didn’t)
1 cup green beans or peas (frozen/pre-cooked)
½ cup black olives
Clean mussels and clams, discarding any broken ones and those that don’t close. Reserve a dozen or so mussels, and steam the rest for 3-5 minutes in a cup of water until they open. Remove the meat from the open mussels and save the broth. Add 2 - 3 cups water and the chicken bones to the mussel broth (+ onion trimmings, parsley stems, etc.) and simmer until needed.
Heat copper paila over a low flame until moderately hot (be careful, this won’t take long) add olive oil, chicken and sausages and sauté over low heat until brown. Remove meats and sauté onion, adding garlic and bell peppers after a few minutes. Then add thyme, paprika and saffron. Return meats to paila and add the rice. Sauté rice for 2-3 minutes, then add 3 cups mussel/chicken broth. Raise heat until the broth boils, then lower to a simmer. Cook without a lid for 15 to 20 minutes, tasting the rice for doneness from time to time (it should be al dente) and adding additional boiling broth if necessary. When about ½ the broth has been absorbed, add the reserved mussel meat and green beans or peas and stir. Then add the clams and mussels by pushing them into the rice. When rice is done, add olives and parsley, turn off the flame, cover paila with a lid, dish towels, etc. and allow to rest for 5 to 10 minutes.
Serve with lemon quarters, salad and wine.
It was great, with no off taste and (obviously) no greenish tint. And we felt fine afterwards… and still do.
I’m not going to use my paila every day, but I’ll make this paella again, and use it for polenta and risotto and jam. Maybe I’ll even make fudge.
 Handout, ArteCobre. The text appears at En Buenos Manos, on line at http://www.enbuenasmanos.com/articulos/muestra.asp?art=125.
 Blumenthal, Dale (1990). Is That Newfangled Cookware Safe? DHHS Publication No. (FDA) 91-2242. On line at
 Master List of Typical pH and Acid Content of Fruits and Vegetables for Home Canning and Preserving. On line at http://www.pickyourown.org/food_acidity_ph_list.htm, and Measuring the pH Value of Meat. Eutech instruments. On line at http://www.eutechinst.com/techtips/tech-tips35.htm Beef reaches its lowest pH 18 to 24 hours after slaughter, after which it rises again.
 Pandell, Alexander J. 1999. The Acidity Of Wine. On line at http://www.wineperspective.com/the_acidity_of_wine.htm