In the eighteenth and nineteenth centuries, it was customary for households to check their copper cookware each year right before the holidays, to see if any of it needed to be sent out for repair. The bottoms of the pans might need to be flattened, rivets might need to be tightened, dents might need to be hammered out and rims might need to be made round again. But most of all, they checked to see if the tin lining was intact or if it had been worn down to the point that the copper was beginning to show through it.
Antique copper cookware is lined with tin. I am not a chemist and not an authority on this subject, but the following summarizes what I have read about it. Copper, at least in small quantities, is actually good for you (it is included in some multivitamins), but too much copper, like too much of many things, is probably not so good (wine comes immediately to mind). The taste of copper leaches into some foods and is not much of a flavor enhancement. And yet, as most cooks know, it is beneficial to whisk egg whites in an unlined copper bowl—they absorb chemicals from the copper that make their bubbles larger and stronger.
Copper & Acid
Foods high in acid can form copper acetates, or verdigris, on copper and this should not be ingested. Verdigris also forms when water is left on copper for any length of time. A tin lining serves as an inert barrier and prevents this from occurring. There are some exceptions to the tin-your-copper rule, however. Although jam is made with fruit high in citric acid, jam makers recommend preparing it in an unlined copper pan; the high sugar content prevents the acid from forming verdigris. Some people take the risk of copper coming into direct contact with food a lot more seriously than others. Julia Child was relatively cavalier about it in volume I of Mastering the Art of French Cooking. She recommended that if copper was showing through the tin the cook should scrub the pot carefully before using it and remove the food as soon as it was done. I always advise people to err on the side of caution. I have had nearly every piece of copper on this site re-tinnned. To be on the safe side, get it re-tinned when and if the tin begins to wear off and expose the copper. When a tin lining is brand new, it is bright and shiny. Over time and with use, it turns a dark, mellow grey. This is normal and not cause for alarm.
The traditional method of re-tinning is very laborious and ends with the inside of the immaculately cleaned pot being hand-wiped with molten tin. Once it has been re-tinned in this manner, you can use the pot for ten years or longer before it may again need to be treated. Of course, if someone were to savage it with sharp, metal utensils, all bets are off. Even thick, traditional tinning should be treated with respect and, whenever possible, stirred and scraped with wooden or plastic implements. If you burn something in your tin-lined pot, just let it soak in the sink until you can gently scrub off the mess. You should always avoid leaving an empty pan on a hot flame since tin begins to melt at around 450 degrees Fahrenheit. Once you have put something in the pot it will be just fine on the fire or in the oven.
metal vs wooden utensils
Most manufacturers today, knowing full-well how careless and lazy we all are, have started lining their mass-produced copper pots with stainless steel because it is nearly indestructible. You can be as rough as you’d like using metal tools on stainless steel, and you can scrape away burned food with a raging fury. I, for one, do not find these compelling advantages. I like my wooden spoons, I’m careful when I do use metal utensils and I’d as soon let the pot soak for a little while if I do burn something (which is a less frequent occurrence since there are no hot spots on copper pans). I have been told that a stainless lining may eventually separate from its copper pot and that once this happens there is no remedy. Since I have never used stainless-lined copper I cannot vouch for the veracity of this statement, but I know that a tin lining that has come to grief can always be replaced.
HOW TO CLEAN and polish
I do put my copper pots in the dishwasher, but I always use either Seventh Generation or Meyers Clean Day dish-washing detergent. They do not have chlorine or phosphate in them, the two ingredients in other dish-washing detergents that can pit copper. Once a pot is clean, I polish it. Sometimes. A little tarnish doesn’t bother me much and if I were a complete fanatic about it I might not use my copper very often. But I don’t let it become badly tarnished; it is so nice to see it shining brightly. I’ve probably used every copper polish on the market by now and will try to make a few recommendations of polishes can be purchased online. Old-fashioned Twinkle works well, as do Copperbril and Legacy of Clean. Currently, Legacy of Clean is my favorite. If you want your copper to really shine, you can follow tarnish-removal with some extra polishing using Wenol Cream. Wenol also helps prevent tarnishing—sort of. There are more aggressive products (some people use The Works toilet bowl cleaner!), but I cannot recommend them. Their fumes may be dangerous and they might be harsh enough to dull your copper. In general, don’t use anything whose smell makes you want to run out of the room.
Before copper polish was available, people used lemon juice and salt. It still works. You put salt on a quartered lemon and rub the pan with it, then wash, rinse and dry the pan. I haven’t tried ketchup, but many people swear by it. Another technique I frequently use: fill a plastic tub with warm water and dissolve some dried citric acid (available online) and salt in it; then dip your copper and leave it for just a few minutes—not longer. You can do quite a few pans, one after the other, this way. Then wash, rinse and dry them. You might want to follow up with some Wenol if a few spots remain or you want it to be shinier.
The most important part of polishing is washing off all the polish or lemon with soap and water as quickly as possible and then drying it thoroughly. If you leave any polish or moisture on your copper it will turn to tarnish. I have carefully polished copper pans and the next day found a sweep of brown tarnish on them, exactly where I did not get all the polish off or did not dry it carefully enough. This is so distressing. And it is so easy to prevent. Be especially careful that there is no water lurking under the handles or rims. It will wait until you have turned your back, sneak down the side of the pot and leave a line of tarnish.
Where to have copper tinned
Where can you find a craftsman to re-tin your pans in the traditional, hand-wiped manner—as well as to perform other repairs? There are more of them around than you might imagine. I have tried several and settled on two that I really like. They charge the same for re-tining: measure down the side of your pan, across the bottom and then up the other side. Multiply the total number of inches by five dollars. Professional polishing is included in the price. All this is explained on their websites.
East Coast Tinning, operated by Jim Hamann in East Greenwich, Rhode Island. I have made many trips down Route I-95 from my home in Maine, with the back seat and trunk of my car rattling with the copper I’m bringing to Jim for tinning, and then driven back home with all the copper from my last trip that Jim has finished. He has never let me down, never done less than a perfect job. I recommend him highly and without reservation. If you live too far away to make door-to-door deliveries, just mail your pots to him.
Rocky Mountain Retinning, operated by Peter and Erik Undiks in Denver, Colorado. Of course I have to mail packages of copper to them, but they get them back to me, in perfect condition, within a few weeks. Rocky Mountain Retinning will always use the traditional, hand-wiping technique unless that is impossible. Fancy dessert molds and teakettles cannot be hand-wiped. There are just too many tight spaces in them. Therefore, when I have copper molds and teakettles that need relining, I send them to Rocky Mountain to be electro-plated, a service that Peter and Erik provide--but only when the traditional wiping method cannot be used. They have asked me to caution all of you that electro-plated tin is not as thick as hand-wiped tin, that you must be particularly careful with it. Luckily, we are less likely to need to scrape the insides of our teakettles and dessert molds than we are our saucepans and skillets.