Removing Firescale/Patina from Copper


Knowing I’ve been working on sprucing up my backyard, our managing editor Shawn Connally kindly gave me her old copper fire pit. Sweet! She also shared with me some great cleaning knowledge she had gleaned from Michael DeJong’s awesome book Clean: The Humble Art of Zen-Cleansing. Turns out that to remove rust patina or firescale from copper, all you need are lemons and salt! Here’s the fire pit, in it’s blackened state, wet down:
fire pit rusty.jpg
Here are our materials (with the lemons cut in half):
Simply sprinkle salt on the wet metal:
And scrub furiously with the lemon halves (hooray for friends!):
The fun part is that you get to see results almost instantly:
The lemons pick up the rust patina/firescale and get yucky:
And the copper shines through!
Rinse and repeat until satisfied! It was fun, smelled good, and is much better for the planet than toxic funk.

16 thoughts on “Removing Firescale/Patina from Copper

  1. Brian Little says:

    Copper doesn’t rust, per se. That brown stuff is called patina, and it’s a bad idea to remove it from outdoor implements. The oxidized brown layer (which would probably eventually turn a lovely green) protects the solid copper underneath from further corrosion. All you accomplish by removing the patina is to expose a fresh layer of copper to the elements, which is no good unless you plan to seal the metal…not really doable with a fire pit.
    The lemon and salt trick works nicely for copper-bottom cookware, though. Use kosher salt if you need better abrasion.

  2. ballookey says:

    Great tip, but I have to agree with Brian on this. That’s patina, and for outdoor copper, it’s definitely more desirable to leave the patina intact. It’ll change over time, but trying to fight it back actually erodes the copper.

  3. Removing Firescale/Patina from Copper Becky Stern says:

    It’s also firescale you’ve got going on there; an oxidation that forms when the metal gets really hot. My boyfriend recently used lemons to clean the copper on a welded sculpture of his, and it worked beautifully. Once he removed the firescale, he could apply an agent that helped it get a green patina instead of a black one, then sealed it with a UV wax to keep it in tact. Goli, you can speed up the natural green patina process with a chemical oxidizer like cupric nitrate (available at your local metals supplier or sculpture house), then when you have fires in it only the portion touching the fire should turn black, not the whole thing.

  4. Removing Firescale/Patina from Copper Becky Stern says:

    also, props to your friend with the “communist party” shirt; Alex has that one too.

  5. Goli Mohammadi says:

    Thanks, Brian, ballokey, and Becky for the correction in terminology–much appreciated! It was a fun experiment to see how it worked, but now I know that patina serves a purpose too. Cheers!

  6. vivi says:

    I don’t know about the “toxic funk”, but it looks like you’re combining CuO + NaCl into green CuCl2, which is considered a poison to aquatic animals, and very toxic to humans. The quantities are insignificant, and I assume you did not eat the lemons, but just so you know. Copper oxide is also quite toxic.

  7. sidecar_jon says:

    I make copper bowls and “fire scale” is a big problem as they need annealing between bashings. I usually use vinegar and salt solution, just left to soak then a stiff wire brush (or pan scourers, though not steel bristles as they go rusty almost immediately)It comes right off leaving dull reddish raw copper which can then be polished with “normal” copper polish.
    To get a pleasing green patina i use a cheap liquid plant food, painted on it goes very green very quickly. Putting in a plastic bag and fuming it with ammonia also works bit is slow.

  8. Atomyk says:

    I don’t know where you think “toxic funk” (hint: combining things that come from the planet) comes from but mixing citric acid (lemon) with sodium chloride (salt)isn’t exactly good.

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I'm a word nerd who loves to geek out on how emerging technology affects the lexicon. I was an editor on the first 40 volumes of MAKE, and I love shining light on the incredible makers in our community. In particular, covering art is my passion — after all, art is the first thing most of us ever made. When not fawning over perfect word choices, I can be found on the nearest mountain, looking for untouched powder fields and ideal alpine lakes.

Contact me at or via @snowgoli.

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