The standard cooking time for eggs in a kettle of boiling water is approximately 6 to 12 minutes, depending on the desired level of doneness. Hard-boiled eggs typically require 10 to 12 minutes, while soft-boiled eggs take around 6 to 8 minutes. The duration is influenced by the size of the eggs and the temperature of the water when the eggs are added.

The reason for this range in cooking time lies in the different stages of egg cooking. When eggs are placed in boiling water, the heat causes the proteins in the egg white to coagulate and the yolk to set. The cooking time needed for each stage varies. For instance, a hard-boiled egg requires more time for the yolk to fully set and the egg white to become firm. According to the United States Department of Agriculture (USDA), a hard-boiled egg should be cooked for 10 to 12 minutes to ensure that the egg white is completely firm and the yolk is fully set. Conversely, a soft-boiled egg is cooked for a shorter period, allowing the yolk to remain runny and the egg white to be slightly firm. The American Egg Board recommends cooking soft-boiled eggs for 6 to 8 minutes for a perfectly runny yolk.

The temperature of the water also plays a crucial role in the cooking time. Water should be brought to a rolling boil before adding the eggs. If the water is not boiling when the eggs are added, the cooking time will be longer. This is because the eggs need to reach the boiling point before they start to cook. Additionally, the size of the eggs affects the cooking time. Larger eggs take longer to cook than smaller ones because they have more mass and volume to heat up.

In summary, the cooking time for eggs in a kettle of boiling water varies based on the desired level of doneness, the size of the eggs, and the initial temperature of the water. Hard-boiled eggs require 10 to 12 minutes, while soft-boiled eggs take 6 to 8 minutes. The United States Department of Agriculture and the American Egg Board provide guidelines for achieving the perfect hard-boiled or soft-boiled egg, ensuring that the eggs are cooked to the desired level of doneness.