Sharper for Longer

How to Care for a Carbon Steel Knife, According to an Expert


May 22, 2019 Home By Photo by Henry Phillips

Magnus Pettersson has been caring for the knives of professional chefs for more than 25 years. He often jokes that he’s a knife doctor, and he both loves and hates carbon steel knives. If you ask him what you would get from a carbon steel knife that you wouldn’t a stainless steel knife, he’ll laugh, “Rust!”

From a practical point of view, chefs use high carbon blades because they can get sharper and hold their edge better than knives made from stainless steel. There’s also a certain level of romanticism, one even Pettersson says he isn’t immune to. “Knives are utilitarian for me. They’re tools,” he says. “Tools that tell stories, and nothing tells a story like a carbon steel knife.”

Now a lead sharpener at new mail-in knife sharpening service KnifeAid, Pettersson likens a carbon steel knife to a pair of worn-in jeans. “I can tell whether the person who owns the knife uses a push cut or pull cut motion, how they store the knife and their dominant hand pretty quickly. It’s beautiful.” Here’s how to take care of a carbon steel blade, according to an expert.

Don’t Sweat the Stains

Stains and rust are naturally occurring when using carbon steel knives. “If you’re bothered by having to wipe the knife every so often while cooking, or mind a little rust, I wouldn’t [use a carbon steel knife],” Pettersson says. “Most nicer stainless steel knives are so good today there isn’t that huge of a difference in edge retention and whatnot.”

Build Patina Early

With his personal knives, Pettersson says the first thing he does is force a patina onto the blade to protect it from rust. “You can do it with almost anything with acid in it: instant coffee, vinegar, potatoes — lots of things,” he says. “Just rub it on the blade and polish them in. This makes a better shield for the steel than whatever it ships with.”

Use Mineral Oil

To prevent rust, Patterson recommends washing your knife shortly after use and oiling the blade. “Food-grade mineral oil is probably the best [oil] you can use,” he says, “many other oils will become like a resin over time and get really, really sticky. [Food-grade mineral oil] doesn’t get that way. It’s always smooth and keeps a good shine.”

Throw Away Your Knife Block

“[Knife blocks] are usually in the kitchen, so they’re in the danger zone,” Pettersson says. “Splashes of water or liquid can get in the block, and some people don’t dry the blade 100 percent before putting them in. This makes the knife block a rust factory, basically.” On top of that, knife blocks are typically breeding grounds for bacteria. Pettersson uses a magnetic strip on the wall to store his knives but also recommends wrapping carbon steel knives in cloth or paper.

Sharpen by Hand

According to Pettersson, anyone who knows how to sharpen a knife by hand or is interested in learning should go carbon steel over stainless steel. “They’re just easier to sharpen than stainless — the metal rubs off more cleanly and doesn’t chip as easily.”

Know Your Knife

Pettersson says knowing the makeup of your knife is the best way to know how delicately you need to treat it. “If you have high-carbon steel knives — like .8 percent carbon and up — they get really reactive to rust. Between .3 and .8 percent, it rusts less and will be a little easier to take care of.”

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