There are several ways to stop tears flowing when chopping onions-
1. Freeze the onions for about fifteen minutes before you slice them. The cold will keep the eye-watering fumes at a minimum.
2. Light a candle next to your work area before you begin slicing your onions. The gasses that make your eyes water will burn off before they reach you.
3. Push a small slice of bread onto the point of your knife and carefully work it down toward the handle. Now when you cut your onion, the bread will absorb the fumes that bring tears to your eyes.
4. Try slicing the onion under running water into a colander in your sink. The running water will actually absorb the odor and make for a less tearful day. (This one's a little trickier than the others—be extra careful when handling your knife under the water!)