High-carbon steel — the traditional material used for making knives centuries before stainless steel was invented — has a mystique and sexiness all its own. In Japan, it was the traditional material for making samurai swords, and then later, kitchen knives. Preparing food with a knife made of carbon steel links you to this 1300-year-old history. Examine the frosty beauty of a knife from Yoshikazu Tanaka or the rustic, raw aesthetic of the Moritaka Ishime, and you too will feel that connection. If you'd like to know more about steel, check out this article from Mike.
Knives made of high-carbon (often just called "carbon steel") steel tend to keep an edge much longer than their standard stainless-steel counterparts. Unfortunately, that extended edge life comes with a trade-off: carbon steel is susceptible to the destructive force that is RUST. (dun dun dunnnnnn) But do not fret; this isn’t the end of the world. Below we will show that you (yes, you!) can own and care for a carbon steel knife successfully. (And so will your children and your children's children as your heirloom gets passed down through generations.)
Like the Fujiwara Denka or Fujimoto Nashiji lines, some knives have a carbon steel core with stainless steel cladding. These knives require less maintenance as the carbon steel is only exposed at the very edge of the knife. "Full-carbon" knives are clad in softer high-carbon steel, which means the whole blade can rust. While the advice that follows is most applicable to full-carbon blades, it's good to follow for any high-carbon steel knife.
What is a patina?
You will find, as I have, that these blades will change colour, becoming grey or even black as they are used. Consider how a copper roof becomes green over time, or a leather jacket becomes more beautiful as it ages. This is called a patina, and it’s a good thing! A patina develops on carbon steel when exposed to air for extended periods of time or to acids for short periods of time. It’s a type of oxidation that helps ward off the evil red rust that eats away at steel and destroys your knife. Black or grey = good, red or orange = bad. If you’re the impatient type, are also ways to speed up the process.
As you use your knives on foods like onions, tomatoes or other acidic food, you will notice the patina getting darker. My carbon knives have a strong patina that I acknowledge as a reward for using exceptional knives, with each blade being unique.
My grandpa had a favourite hunting knife. When he’d come home from a hunting trip, he’d wash it, run it over a sharpening stone, and oil it with Camellia oil. It is 100% food-grade, considered hypoallergenic, and it won’t go rancid the way many food-grade oils can. Applying a few drops to your knife weekly for the first few months will keep the steel from oxidizing due to moisture (destructive red rust) but still allows a healthy patina to develop.
There is a term used by chefs in the culinary world: “Mise en Place”; everything in its place and a place for everything. When I set up my cooking station, it always includes two towels, one damp and one dry, folded up next to my cutting board. The former for wiping food residue off my blade, the second to dry the blade to prevent rust. It is super easy to get into this “one-two” habit of wiping off your knife as you work. While I’m prepping, I generally wipe my knife whenever I wash my hands or between different foods. When I'm finished prepping, I wash my knife with soap and water, taking care not to scrub the patina off my blade. Dry your knife well, and store it safely!
How to Remove Rust from a Carbon Steel Knife
Did you find rust on your blade despite being a good student and adhering to everything you’ve learned here? No worries! Knifewear Rust Eraser or a gentle kitchen scrubby can usually get that right off. If it’s a more serious case, you can also gently rub the blade with Bar Keepers Friend, baking soda, or even some 1000 grit sandpaper. Use a gentle touch, so you aren’t taking off all the patina you developed.
Knifewear rust eraser in action. Pretty cool, right?
Why Do You Want a Carbon Steel Knife?
This might all sound like a lot of work for a simple kitchen knife, but I promise it’s worth it. I like to think of a new carbon steel knife like a puppy. A brand new puppy might pee on the carpet; a carbon steel knife might rust. When you train a pup, yes, you’re training your dog, but you are also training yourself to engage in good habits. Provided things go well, your day-to-day life with your dog becomes more fun than work, and everyone is happy. It's the same with these knives. The connection to one’s tools and their history makes everyday prep work a joy to partake in. I don’t know about you, but when I enjoy a job, that job gets done more often and with more care than those I don’t.