How to cut onions without crying

I tried all the old tricks to keep my tears at bay when chopping onions: sunglasses, swimming goggles, sticking out my tongue, leaving the faucet running, and slicing onions straight from the fridge. But nothing seemed to really stop the crying until I invested in new, sharper knives.

That’s no coincidence. A sharp knife allows you to cut an onion “cleanly and efficiently,” according to Henry Liu, founder and CEO of Cangshan Cutlery. Liu explains that when you use a dull knife, you crush more of the onion, which releases more tear-inducing chemicals. “A sharp knife makes precise cuts, which locks in the onion’s juice and minimizes irritation,” Liu says.

Why a sharp knife reduces tears

A razor-sharp blade “does minimal damage to the onion’s cell walls, which release the sulfuric acid (which causes tears),” says Boston-based chef and restaurant owner Jason Santos. Plus, “a sharp knife reduces the amount of time you spend cutting,” says Chelcea Dressler-Crowley, vice president of Messermeister. That means you spend less time dealing with onion gas and juice, and are therefore less likely to get tears.

Home cooks should invest in at least one quality chef’s knife for their kitchen. Santos says the brand is not as important as the cook’s preference. He points to HexClad, for example, because the blades are ultra-thin. “You can control your cuts more precisely, which gives you a more consistent product,” he says.

Regardless of the brand, the knife should always be razor sharp. This not only prevents cracks, it is also simply safer.

“There’s nothing more dangerous in the kitchen than a dull knife, and I think you realize that early in your career,” says Santos. Using a sharp knife requires less force, reducing the risk of slipping and cutting yourself, adds Liu.

There are a few practical ways to test how sharp your knife is. The first is the paper test, says Dressler-Crowley. “Slowly drag the knife along the length of the paper until you’ve cut through it,” she says. “If your cut is jagged and uneven, your knife is not sharp. If your knife makes a clean cut through the entire length, it is properly sharpened.”

Liu cites the tomato test as a practical way to test the sharpness of a knife in the kitchen. “Try cutting a ripe tomato,” he says. “A sharp knife will glide effortlessly through the skin, while a blunt one will be difficult to reach.”

How often you should sharpen your knife

There are two ways to maintain the sharpness of your knives: honing and sharpening. “Think of honing as blade maintenance and alignment,” says Liu. Honing actually restores the edge of the blade. Regular sharpening depends on how often a home cook uses their knives, but in general, you should have your knives professionally sharpened at least once a year, and do regular honing in between, says Liu. “Regular honing with a whetstone before each use helps maintain the edge between sharpenings.”