Hard-boiled eggs are a convenient and nutritious addition to meals, but many home cooks are puzzled when their yolks develop an unappetizing green-gray ring. This discoloration, though harmless, is the result of a chemical reaction between the iron in the yolk and sulfur in the white, which occurs when eggs are overcooked. While it doesn’t affect safety, it certainly affects the egg’s visual appeal. Luckily, avoiding this is simple with a few precise steps. Start by placing eggs in a pot of cold water, covering them by 3 to 5 centimeters. Heat the water gradually over medium heat and, once it reaches a full boil, immediately remove the pot from heat. Cover and let the eggs sit in the hot water for 9–12 minutes depending on size.

To stop the cooking process and prevent the green ring, transfer the eggs immediately into a bowl of ice water for about 5 minutes. This shock cools them quickly and also makes peeling much easier. Peeling under running cold water can further ease the process. For optimal results, use eggs that are 5 to 7 days old, as fresher eggs tend to be harder to peel. A pinch of salt or splash of vinegar in the boiling water can help reduce cracking. Once cooked, store eggs in their shells in the fridge for up to a week, and peeled ones for 2 to 3 days. The real secret lies in proper timing and immediate cooling—no fancy skills needed, just a bit of precision.