Cooking

Cooking in Copper: Polishing With Ketchup

It's both a secret and the best shared tidbit among copper collectors and newbies to the metal: ketchup cleans copper.

I say this with a caveat. Ketchup doesn't clean blackened copper, burned and oxidized dark with use over the fire for years, or scorched copper bottoms that haven't been polished in decades. Ketchup polishes relatively clean copper, or copper with the early deep bronzing of use over a gas or wood stovetop. It removes that first bit of oxidation and removes the blush of the developing patina with the oxalic acid within the ketchup itself. Citric acid plays a part to some degree, but the oxalic acid does the real trick.

The property of oxalic acid in rhubarb working its magic on copper was also discovered by Bob (the master tinsmith) at a reenactment when he put a spoon covered in rhubarb sauce in a copper pan. A while later, he removed the spoon to find a bright oval of clean copper under the spoon. That oval stayed there a long time!

If you find that ketchup alone doesn't completely do the trick, you can make a paste of ketchup with some vinegar and flour added to create a thicker polish. Leave it sit on the copper until it starts to get tacky, and then wash it off. Don't use salt unless you are okay with the light etching that is likely to occur (unless you get the super fancy salts or super fine French salt…that's less likely to leave a mark).

The beauty of ketchup, rhubarb, vinegar, flour, and even a potato, is that they are all-natural and even organic cleaning tools so you don't have to worry about keeping these materials away from a tin lining. If you do decide to use a chemical cleaner, be careful to keep them away from the interior lining: it can etch, discolor or even strip a few layers off of the interior metal due to the abrasiveness and chemical compounds themselves.

What if you do have a vintage piece or something very old that is blackened by time and use? Well, invest in some power tools and acid and start cleaning! Actually, you can send to a restorer who can clean up the deep oxidation which have bonded to the copper. It all comes off, but it needs more than elbow grease at some point.

But if you have something moderately in good shape, and it's obvious it's a copper pot, you can probably make a good dent in shining it up with nothing but the ketchup in your refrigerator! Now you know the secret, too!

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Copper Safety

We should discuss copper cookware and safety, because that has been brought up so many times over the years, as a cookware maker, that I feel like the internet can't be populated enough with facts (since there is SO much mis-information out there). So, take it from me, someone who makes the stuff, that these are the basics about copper cookware and safety, quick and handy.

Copper cookware has been around for hundreds of years (and crazy enough, a lot of it is still around and can be used on our stoves yet today!), and copper in plumbing and other vessels even longer. And it's true that copper has proven to be anti-viral and anti-bacterial (see studies, try not to get cross-eyed with the science 🙂 ). This particular property of copper is also best shown in food situations when used with a food or liquid with a neutral pH, like water. There are those who believe leaving water in a pure, unlined, copper cup overnight purifies the water and they drink it in the morning for the extra health benefit they believe it purports.

And there's no reason not to consider that it's definitely a solid possibility!

There was some talk a while back about drinking alcohol in unlined copper Moscow mules mugs could cause copper poisoning, but the truth of it is, you'd need to drink a lot of Moscow mules out of unlined copper mugs a few times a day for a few decades before you saw any copper poisoning issues (and don't take my word for it: read here for details from a chemist).

But we're going to focus now on cooking in copper, and what it means to cook in it, and to be safe while doing it.

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Cooking is where the chemical reaction to your food happens, and where the food molecules shift and change. It's worth having a pure, organic, non-reactive place to have that chemical reaction, don't ya think?

Tin is inert, meaning it's non-reactive. Nickle and stainless steel are also rather non-reactive in comparison to copper, which is reactive. That's why you can get copper leaching into your food when you heat it up and create a chemical reaction not only with your food but with your cookware AND your food. Hence…you want copper cookware because it's fast, energy efficient, precise, and pure…but you want it lined to keep the chemical reaction in the pan happening between your food and nothing else.

Make sense? Easy, right?

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Copper Cookware Cleaners

I am by no means a chemist, nor a science major, nor even a chef.  But I do like to research, and I do like to compile information (thankfully my book genre is historical fiction so I get to channel that nutty history obsession habit).  Cleaning pure metal copper cookware is a topic that fascinates me, mostly because so many people don't know some of the basics, and it's truly incredibly easy.

I am not going to get into cleaning of interiors, as tin-lined copper cookware requires different cleaning than stainless lined copper cookware.  That'll be another post.  So to be safe, generally plan to use all the methods below on the copper body, but not the insides.

Here are some favorites, or are listed highly on forums.  If you like having copper that looks vintage or has a deep patina, you should completely ignore the rest of this post.  If you like to clean your copper cookware, or your copper sink, or your collectable copper molds, read on.  And, as always, I welcome thoughts, feedback, and even results!

  1. Organic copper cookware cleaner:  This one's easy.  Use organic copper ketchup!  Or regular ketchup works too.  This method generally is best for newer copper, or copper that doesn't have much patina on it, as it is relatively superficial and won't dig deep into the copper crystals to pull out the oxidation (see, I had to get some sort of metal geekness in there). **because this is just food, you could use it on the tin or stainless interior, though it won't react and give you the same polish as it will to the copper.
  2. One step further: Use ketchup with fine sea salt (make sure there's no ingredient in the salt that is a silicate which can scratch the copper)
  3. Our friends at Brooklyn Copper Cookware recommend doing a paste of flour, ketchup, salt and a dash of vinegar to create an even more intense and thicker paste for deeper, but natural, polish.
  4. Using half a lemon with salt has also been used to clean the copper.  Or lemon and vinegar.  Measurements vary. Generally elbow grease is needed!
  5. Tarnex followed by MAAS.  Clean the copper pot (not the interior lining) with the Tarnex solution and then quickly use MAAS, a polishing paste you can buy on Amazon.  Don't wait too long after using the Tarnex to polish, as the Tarnex will only get the oxidation off, but it will return relatively quickly without the polish application.
  6. Wright's Copper Polish has been touted to give a great polish job on the copper as it is not abrasive.
  7. Many people swear by some of the following polishes as well for the copper exterior: Bar Keeper's Friend, Twinkle, Brasso, Wright's Copper Polish, Flitz, or Red Bear.
  8. The master smith I apprentice under turned me onto Eve Stone Antique's Copper & Brass polish.  That stuff makes copper look like a mirror, plus it holds a shine for a LONG time.

If your copper is beyond anything you can do in the comfort of your home (or the ventilated area of your garage), you can always send it off to be professionally polished.  Many tinners/re-tinners will do that after they re-work the interior.  For those of you with stainless steel interiors, simply finding a local coppersmith or metalsmith might do the trick, or you can send your copper to us at House Copper for polishing!

Happy shining to you all!