Why Do Hard-Boiled Eggs Get a Green Ring Around the Yolk?

You whip up a batch of hard-boiled eggs, excited for your salad… only to discover an unappetizing green ring circling the yolk. It’s a common sight—but definitely not an appealing one. Even if you follow the cooking directions to the letter, this pesky problem can still crop up. So what causes it, and how can you prevent it without needing chef-level skills? Let’s break it down and learn how to make perfect hard-boiled eggs that look as good as they taste.

The Science Behind the Green Ring

That greenish ring isn’t a sign your eggs have gone bad or that you’ve ruined your recipe. Instead, it’s a harmless chemical reaction between the iron in the yolk and the sulfur in the egg white. When eggs are overcooked, these elements combine to create iron sulfide, which is safe to eat—but not so pretty to look at. Thankfully, avoiding this reaction is simple with just a few tweaks to your cooking method.

How to Cook Perfect Hard-Boiled Eggs

Start with cold water.
Place your eggs in a single layer in a saucepan. Add enough cold water to cover them by 3 to 5 centimeters.

Heat gently.
Bring the water to a boil over medium heat. As soon as it reaches a rolling boil, turn off the heat.

Let them sit.
Cover the pan with a lid and allow the eggs to sit in the hot water for 9 to 12 minutes. If you prefer a softer yolk, 9 minutes is plenty. For fully set yolks, leave them for up to 12 minutes.

Cool quickly.
While the eggs are resting, prepare a bowl of ice water (or very cold water if you don’t have ice). Transfer the eggs straight into the cold water once their resting time is up. Rapid cooling stops further cooking, helps prevent the green ring—and makes peeling a breeze.

Peel under water.
After cooling for about 5 minutes, gently crack and peel the eggs under running cold water. This helps remove stubborn shell pieces and keeps the egg whites smooth.