This Is the Best Way to Cut Onions Without Crying, New Research Reveals

Home cooks have shared countless tricks to stop themselves from crying while cutting onions, from chilling them in the fridge beforehand to using a fan to blow away the vapors to wearing a pair of goggles to protect their eyes. But researchers at Cornell University may have just determined the best, scientifically proven way to stop the tears from flowing.

According to a physics paper published on arXiv, an open-access archive for scholarly articles, using a sharp knife while making slow, controlled cuts seems to be the best way to minimize tears when chopping onions.

When onions are cut, they release a compound known as syn-propanethial-S-oxide that triggers the nerves responsible for producing tears. So a team of physicists decided to study how the compound gets released, visualizing and quantifying droplet ejection during onion cutting.

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To do this, researchers coated onions in black spray paint to make it easier to see and track what was happening as the onions were cut. They then set up a high-speed camera and started chopping.

Using a custom guillotine, researchers experimented with cutting speeds ranging from 1.3 and 6.5 feet per second and blade thicknesses between 5 and 200 millimeters. They found that the thinner, sharper blades, which moved more slowly and with less energy, produced fewer droplets. On the other hand, thicker, duller blades caused an explosion of high-speed particles that could head straight into your eye.

Because the duller blades bent the onion’s skin before cutting, there was a build-up of pressure that resulted in a more powerful release of juice. Duller blades produced as many as 40 times more particles than the sharper blades, and faster cutting speeds produced up to four times as many droplets as slower speeds.

The researchers also experimented with onions refrigerated for 12 hours, finding that the chilled onions released a "noticeably larger volume" of droplets compared to room-temperature onions, debunking that common belief.