How to Chop an Onion Without Crying, According to Experts

I’ve tried all the old tricks to keep my tears at bay when cutting onions: sunglasses, swimming goggles, sticking out my tongue, running the sink faucet, and slicing them straight out of the fridge. But nothing seemed to really stop the sobfest until I invested in new, sharper knives. 

This is no coincidence. A sharp knife allows you to slice through 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 end up crushing more of the onion, which releases more tear-inducing compounds. “A sharp knife makes precise cuts, which keeps the onion’s juices contained and minimizes irritation,” says Liu. 

Why a sharp knife reduces tears

A razor sharp blade “will be minimally invasive on bruising the cell walls of the onions, which release the sulfuric acid [that causes tears],” says Boston-based chef and restaurateur Jason Santos. Additionally, “a sharp knife reduces the amount of time spent cutting,” says Chelcea Dressler-Crowley, vice president of Messermeister. This means less time exposed to the onion gas and juices, and therefore a reduced likelihood of tears. 

Home chefs should invest in at least one quality chef knife for their kitchen. Santos says that the brand isn’t as important as the chef’s preferences. For example, he points to HexClad because the blades are ultra-thin. “You can control your cuts with more precision, which will give you a more consistent product,” he says. 

Regardless of the brand, the knife should always be razor sharp. In addition to preventing tears, it’s simply safer. 

“There is nothing more dangerous in a kitchen than a dull knife, and I think you realize that fast and early on in your career,” says Santos. When you use a sharp knife, you’re able to exert less force, and thereby reduce the chance of slipping and cutting yourself, adds Liu. 

There are a couple handy ways to test how sharp your knife is. The first is the paper test, says Dressler-Crowley. “Slowly pull the knife down the length of the paper until you cut through it,” she says. “If your cut is jagged and uneven, your knife is not sharp. If your knife makes a clean cut all the way down, then your knife is properly sharpened.” 

Liu points to the tomato test as a practical way to test knife sharpness in the kitchen. “Try cutting through a ripe tomato,” he says. “A sharp knife will glide through the skin effortlessly, while a dull one will struggle.”

How often to sharpen your knife

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