The green ring around a hard-boiled egg yolk is caused by a chemical reaction between iron in the yolk and sulfur in the white. This happens when eggs are cooked at too high a temperature or for too long, creating a harmless but unsightly discoloration. Understanding this simple science allows you to adjust your cooking method to avoid the ring.
By gently boiling eggs and cooling them quickly in ice water, you halt the reaction before it begins. This careful approach results in bright yellow yolks, free from greenish-gray rings. Mastering this technique transforms your eggs from frustrating to flawless, making every meal visually appealing and delicious.