Martha Stewart's Trick To Prevent Onion Tears Brings On The Heat (Literally)

Everyone has their own trick for preventing onion tears — including Martha Stewart, who shared her simple solution to avoid weeping while chopping alliums back when syndicated TV shows were the thing, and she had one. Stewart's onion-chopping advice recently resurfaced on TikTok, and it couldn't be more simple. 

Stewart advised, "Slice onions as close to an open flame as you possibly can," adding that this technique allowed her to chop 20 or 30 pounds of onions in one sitting back when she was catering and never caused her to shed a tear. As Martha chose to open her own catering company after a career as a stock broker, and obviously wasn't put off chopping onions as part of that job, all evidence suggests that cutting onions near a flame can prevent tears, even though cold onions are apparently less irritating.

In the video, Stewart gives this advice while chopping onions near a relatively low flame from a gas burner. So it would seem that the flame technique doesn't need to be at inferno level to work. In fact, if you have a candle lying around, it might work. Of course, if you're slicing 20 to 30 pounds of onions, you may need more than one tealight; hopefully, there's a multi-pack in a cupboard somewhere.

In order to understand why Martha Stewart's onion hack works, we have to understand why onions makes us cry. The science actually pretty complicated: The cells of onion flesh contain enzymes in a sealed vacuole (which is like a little pouch). When the vacuole is pierced, the enzymes mix with other chemicals inside the onion cells, and together, they create a sulphine (a molecular compound that contains sulphur) which is released into the air and irritates our eyes. Is that enough chemistry for you? I'll move on to physics, then.

As those irritating molecules are light, they're easily removed by air flow. So if you chop onions outside on a windy day and the wind is blowing away from you, you're probably good. Open windows might also help, as might a fan. But fire consumes oxygen, so it pulls in any air (and accompanying molecules) and eliminates the sulphine.

With a gas burner or a candle, you need to be near the flame for it to work, which might be why some kitchen workers apparently like to chop onions with a match between their teeth. I personally wouldn't do that, but hey, I don't have to chop as many onions as Martha Stewart did in the '90s, let alone slice and dice as many as a prep cook in a popular restaurant.

Martha Stewart has tricks for everything from saving money on olive oil to the perfect tool to separate eggs. And she's developed some of them by listening to other people's great ideas. You'll find some of them on her website, where she has collected a bunch of tear-free onion chopping advice that align well with the science we just learned.

Martha suggests soaking your onion in cold water before cooking, microwaving your onions, and chilling them. All of these options slow down, minimize, or neutralize the enzymes, so they're less likely to cause anyone but the most sensitive weep. Other experts like to chop onions submerged in water, although this seems dangerous if your knife skills rank below expert. It should work if you can do it, though, as the molecules that make you cry won't make it out of the water. If you have a good vegetable peeler, it might be a safer option when submerged — using a peeler on onions is great for thin, even slices. 

The final solid piece of advice (and to my mind, most important) from both Stewart and others is to cut well and minimally with a very sharp knife. A sharp knife will cut the onion with greater precision and cause those compounds to mix less well; a smooth cutting action should also spray less liquid into the air. However, if your knives (and knife skills) aren't on par with Martha Stewart's, her open flame method — or a fan or open window — might still keep your eyes from tearing.