How we tested
As serious cooks, we’ve always been intrigued by knives made from carbon steel. This alloy is considered superior to stainless steel by many chefs and knife enthusiasts because it is believed to be harder and stronger and able to take on—and retain—a keener edge. But as practical cooks, we’ve been a bit skeptical. Carbon steel is a high-maintenance metal that rusts if not kept dry, so the makers of carbon-steel knives recommend drying the blade immediately after washing it; some even suggest wiping the blade dry between cutting tasks or occasionally coating it with mineral oil to ward off excessive oxidation, which corrodes the metal. Given that our longtime favorite stainless-steel chef’s knife is virtually maintenance-free, that’s asking a lot.
Still, we wanted to know if carbon steel was truly a cut above stainless. We singled out eight carbon-steel chef’s knives, a mixture of Western- and Japanese-made blades, priced from $72.99 to a staggering $299.95. We recruited seven testers of various abilities to put the knives through our standard cutting tests: mincing parsley, dicing onions, quartering butternut squash, and butchering whole raw chickens. Before and after each round of tests, we sliced through sheets of copy paper; whether the blade cleaved smoothly or dragged indicated how well its edge held up. And all the while, we noted the overall user-friendliness of each model, particularly with regard to the handle.
Battle of the Blades
Some knives had sharp spines or handles that pressed painfully into our palms and caused fatigue. Better grips offered what ergonomists call “affordance”: a shape and texture that allow multiple grips, so hands of all sizes feel comfortable and secure.
As for the meat of our testing—the blade—we homed in on sharpness, which is determined by two factors. First, the thinness of the edge, which is measured by its V-shaped angle. Simply put, the narrower the angle, the cleaner and more precise the cuts. Our top-ranking knives, which were sharpened to between 10 and 15 degrees on either side of the blade, slid through food, while we had to use more force with wider blades that were sharpened to 20 (or more) degrees on either side.
The second determining factor, the strength of the metal, depends on the type of steel that’s used and how it is heat-treated. Manufacturers wouldn’t disclose this information but did share their blades’ Rockwell scale ratings—a measurement of the metal’s strength in a unit called HRC (HR stands for Hardness Rockwell, and strong metals like these are in the “C” class). Sure enough, the highest and lowest Rockwell ratings—60 and above, and as low as 52, respectively—corresponded to the blades’ performances. In fact, our bottom-ranking knife was dull out of the box, with testers comparing it to “cutting with a spoon,” and quickly lost what little edge it had.
To understand why harder blades performed better, we took copies of the knives to Mike Tarkanian at the Massachusetts Institute of Technology’s Department of Materials Science and Engineering. Using a high-powered digital microscope, he zoomed in on the edges of the bottom- and the top-performing blades, which had the lowest and one of the highest HRC ratings, respectively. Immediately we could see why the bottom-ranking knife failed: Even new, its edge looked rounded and dull. Conversely, the top-performing knife’s edge looked as taut as fishing wire, which explained its razor-sharp performance.
Knowing how the carbon-steel knives stacked up against one another, we circled back to our original question: Can carbon steel actually perform better than stainless steel? We decided to pit the best carbon-steel performer up against our favorite stainless-steel knife. We took a brand-new copy of each and tested blade durability by placing a plastic cutting board on a scale (to ensure that each cut would incur the same amount of pressure), making rocking cuts, and repeating the paper cutting test every 10 strokes to track changes. When both blades were still equally sharp after 5,000 cuts, we cut up five more whole raw chickens and butternut squashes with each and then sliced delicate tomatoes. Again, it was nearly impossible to pick a winner. Only after we repeated the scale test on a glass cutting board—hazardous to knife blades—did the knives start to wear down. The carbon-steel model edged out the stainless (which has a Rockwell rating of 56 and a 15-degree edge), but only slightly; both knives still sliced onions with ease.
Their near-identical performance made us strongly suspect that how the metal is manufactured is more important than whether it’s carbon or stainless—a hunch that was confirmed by images of the metals’ grain structures taken at the Boston University Photonics Center. Both looked similarly fine and tight, indicating strong, durable blades.
Given our findings, we can’t justify buying a carbon-steel knife—especially since our favorite stainless-steel model is a bargain and requires no fussy upkeep. But if you are willing to pay a premium and care for carbon steel, our winner is a showstopper. Its razor-sharp blade, sloping ergonomic handle, and good looks make it both visually stunning and a pleasure to use. Our Best Buy is a shade less sharp than our winner, but still impressive.
Seven test kitchen staffers subjected eight chef ’s knives (with blades as close to 8 inches as possible), priced from $72.99 to $299.95, to a battery of kitchen tasks to assess sharpness, comfort, and overall performance. Manufacturers supplied Rockwell ratings (a measurement of the metal’s hardness in a unit called HRC) and blade angles. Scores from each test were averaged to get the overall rating; knives are listed in order of preference. Prices were paid online.
CUTTING: We minced parsley, diced onions, quartered butternut squash, and butchered whole chickens, carrying out each task 70 times per knife. Narrow, razor-sharp blades that cut swiftly and evenly rated highest.
COMFORT: Knives with smooth, nonangular handles of medium width and length rated highest. We also preferred blades with rounded top spines that didn’t dig into our fingers.
EDGE RETENTION: We sliced through paper before and after each round of cutting tests. Blades that kept their original sharpness rated highest.