How to Sharpen Kitchen Knives the Right Way

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Sharpening a chef's knife manually doesn't have to be a daunting task. We asked a guy who sharpens 100 knives a day to show us the way.

Vincent Lau's job is to restore and maintain the blades of hundreds of clients a week, many of who belong to New York City's culinary elite. When we met at Korin, a Japanese knife and kitchenware emporium in Tribeca where he does his work, he was just finishing up a set of 104 steak knives from Eleven Madison Park (considered by many critics to be one of the world's best restaurants). But he wasn't using some automatic, industrial sharpener. Lau favors the time-tested techniques of traditional whetstone sharpening — even if it's slower.

"Using a whetstone to sharpen knives isn't really comparable to using a machine or knife sharpening tool," Lau says. "Machines can't accommodate any type of knife with any level of defect or dullness. I can." We asked Lau, who "easily sharpens more than 100 knives a day," the steps he takes to revive a knife, and what you need to do it at home.

Whetstones are differentiated by grit numbers. The lower the grit number, the coarser the stone. "Lower numbers are coarser and should be used on the first sharpen. Higher numbers are typically only used to finish an already sharp knife," Lau says. A grit number below 600 is typically reserved for repairs or extremely dull knives, so Lau recommends starting with 1,000 for the initial sharpening.

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Finishing a knife is the process of eliminating the burr you create by removing metal from the previously dull knife (it also makes the knife more reflective and good-looking). Swap your lower-grit-number stone out for something higher. Lau recommends anything in the 4,000 to 8,000 range. If you don't feel like spending almost $200 on two whetstones, King makes a two-pack (1,000 grit and 6,000 grit) for $42.

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The first thing any would-be knife sharpener does before putting blade to stone is study the blade itself. Ask yourself, Where is the knife dull? Is it single or double-beveled? Carbon steel or stainless steel? "Don't just pick up a knife and go," Lau says. "Pay attention to what you’re doing. You’ll learn to adjust to variables with practice."

Soaking the stone before sharpening ensures the surface of the stone won't scratch or chip the blade further. According to Lau, it is a non-negotiable step in the knife sharpening process. "I’d soak them for at least 15 minutes or so before getting to work," he says. "Half an hour would be ideal."

"Keeping a consistent grip is the first step to not injuring yourself," Lau said. In your knife hand, Lau recommends putting your thumb on the spine of the blade, your index finger on the heel and keep three fingers wrapped around the handle. Your off-hand will be used as the sharpening force.

This is the most difficult step for beginners. "Every knife has a slightly different angle that the edge slopes down to, so you’ll have to learn how to feel for that," Lau says. To find the angle, lay the knife completely face down on the stone and put two fingers on its edge. With your fingers keeping the blade's edge on the stone, use your other hand to lift the knife until you’ve found the shallowest angle that allows the edge to be flush with the stone. "You’re trying to match the bevel's angle with the stone," Lau says. "This will take practice."

Beginners can use a stack of two to three pennies as a visual guide. Place the pennies on the sharpening stone and lay the spine of the knife on top of them. "In my lessons, that really helps people visualize what they need to do themselves," Lau says.

Once you’ve got the angle down, it's time to create a new edge. Lau recommends getting comfortable with the motion and pattern of sharpening before working on your first knife. In theory, the process is quite simple: keep the knife against the stone with two fingers and pull the blade towards you, then push it away.

Two things to think about in this up-and-down movement: The sharpening action is on the downstroke (pulling the blade toward you), so relieve pressure on the knife on the upstroke. And you need to sharpen the entire blade, so slide your fingers slightly down the blade with every downstroke; if you’re not applying pressure to a point on the blade, it's not sharpening.

Lau says to make sure the tip of the knife doesn't miss sharpening, too, as the optimal sharpening angle for the rest of the blade can create a gap between stone and tip. To counteract this, simply lift the elbow of your grip hand while sharpening the tip area — this will lower it onto the stone.

To prevent damaging a knife, Lau splashes his sharpening stone with water constantly before and after a round of sharpening. A sign you’re in good shape: grey sediment building up in the water on top of the stone after a few swipes of the blade. "That stuff is abrasive and helps you sharpen more efficiently," Lau says. "Don't wash it off."

Finishing a knife happens just like the initial sharpening, the only difference being the stone used and the pressure you apply to the blade. Lau says instead of pushing down on the blade across the stone, apply only the pressure of the weight of your hand. "Any more than [the weight of your hand] and you’ll run the risk of damaging your newly sharp knife," Lau says.

It may be cliché, but slicing through a sheet of paper is still the easiest way to check your work after sharpening. "If you carve through the paper without issues, it's sharp," Lau says. "Make sure you run the whole length of the knife, too, because if you left any chips or dull spots you’ll feel the drag while cutting."