How to chop onions without crying

I recently attended a dinner party where we decided to make some guacamole from scratch together. It was then that I found out that one of my friends didn't know how to chop vegetables. Eager to learn and pitch in, he took up chopping the tomatoes, while I volunteered to demonstrate how to dice the most notorious veggie on the chopping block: the onion.

The basics: How to dice an onion

You might wonder how much explanation is really required for this basic task, but there is actually a decent amount of technique to it (though for those of you who have been chopping veggies all your life, the following section might be more interesting). I first learned how to mince an onion by watching the masterful Jacques Pepin on PBS, and this technique was later reinforced by watching the meticulous folks at America's Test Kitchen (gotta love PBS cooking shows!). Here's how to do it:

1) I actually start first by chopping the onion in half from stem to root, even before I peel it. This makes it a lot easier to do the peeling step next.

2) With the onion cut in half, it's easy to see and get at the dry papery layers on the outside and peel those off. Then I go and give the onion, cutting board and knife a rinse at the sink cause this thing was in the ground, so who knows what's on it. Place your onion halves flat side down and it should look like the following:

3) Next chop off the stem end of the onion as shown, but leave the bottom of the bulb in tact. It will serve as a nice handle to grab on to the onion while you chop and also helps to hold the layers together better.

4) Then start making vertical cuts into the onion, a little over a 1/4" apart (varies depending on how finely you're trying to dice). Don't cut all the way to the bottom part of the bulb so that your onion stays in one piece.

5) Follow that up by making horizontal cuts a little over a 1/4" apart (perpendicular to your previous set of cuts). Once again, don't cut all the way across through the base of the bulb. This step tends to be a little trickier cause there's a lot more moving parts and you can't just count on gravity to do most of the work. Your life will be a lot easier if you have a nice sharp knife to work with (just make sure you don't cut towards your hands!).

6) By the end of step 5, you should have a grid of cuts in your onion. You finish off the dice by slicing off grids of onion cubes (see below) until all you have left is the nubby base of the onion that you took care to leave in tact.


Now, if you don't take any special precautions, somewhere along step #4, or even earlier if you have a particularly lachrymose onion, your eyes will probably start to feel the burn, which leads to the question:

Why do onions make us cry?

Onions absorb sulfur from the ground for nutrients. When you chop an onion and break open its' cells, that releases enzymes which react with sulfoxides in the onion and result in a gas called propanethiol S-oxide. This gas wafts up to our faces as we chop and when it reaches the liquid of our eyes, it produces a mild sulfuric acid. That of course isn't friendly stuff to the eyes, so our body starts working to flush it out by producing tears.

Though not all onions are real tear-jerkers though. Ones such as vidalias which are usually in less sulfuric soil tend to be less potent.

Now, how to do it without crying

There's a lot of tips out there for preventing the tears ranging from burning a candle next to your chopping board to cutting under water (if you can do everything I described above under water, I'll be impressed!). Here's the ones that I've found to work well:

A) Store your onion in the fridge before chopping. The cooler temperature slows the enzymatic processes that cause the sulfuric gases.

B) Use a very sharp knife. As described above, the gas is released when cells are broken. A dull knife not only slows your work and prolongs your exposure, but breaks more onion cells as you try to bludgeon your way through the thing.

C) This one is probably the most effective, but funniest looking - you don't even really need to do A and B if you do this. Wear goggles while you chop. The best way to prevent the burn in the eyes is to stop the gases from getting there in the first place. Ski goggles work pretty well cause they block enough fumes while being relatively comfy. You'll look a bit sillier but feel much better in the end.


Unfortunately, that day at the dinner party I was using an onion that was kept at room temperature (doh), and I was using a pretty dull knife (double doh - made me wish I carried around my own knife set like one of the pros on Top Chef). Being too self-conscious to put on a pair of goggles, I decided to tough it out. That didn't last very long. Chopping a gigantic sulfuric onion with a dull knife is a kind of culinary torture second only to accidentally rubbing your eyes after chopping a hot pepper. So, having just come from a swim, I caved and whipped out the swim goggles which not only gave me much relief, but provided lots of entertainment for my fellow diners.