What Causes the Green Ring Around Boiled Egg Yolks?

That greenish-gray ring forms when eggs are overcooked or cooked at too high a temperature. It’s caused by a chemical reaction between the sulfur in the egg white and the iron in the yolk, creating ferrous sulfide. While harmless and safe to eat, it’s not very appealing to look at.

### Choose the Right Eggs

Eggs that are a week or two old are easier to peel than fresh eggs because the pH level changes, allowing the white to separate more easily from the shell.

### The Best Method to Boil Eggs

1. Place eggs in a single layer in a saucepan.
2. Cover them with cold water (about 1 inch above the eggs).
3. Bring the water to a full boil over high heat.
4. Once boiling, **turn off the heat**, cover the pot, and let the eggs sit in the hot water:

* **Large eggs**: 10–12 minutes
* **Medium eggs**: About 9 minutes
* **Extra-large eggs**: Up to 15 minutes
* For slightly soft yolks: 7 minutes