Why does a green ring appear around hard-boiled eggs?

Let the eggs sit in the hot water, covered, for about 10 to 12 minutes, depending on their size. This gentle cooking method allows the eggs to firm up without reaching the high temperatures that cause the green ring. Once time’s up, it’s all about stopping the cooking process.

Transfer the eggs immediately into a bowl of ice water or run them under very cold water for several minutes. This quick cooling prevents the iron and sulfur reaction from continuing and makes peeling much easier.