4 minutes for slightly set yolk and set white. 5 minutes for a medium cooked firmer yolk and white. 6 minutes for hard boiled with lightly soft yolk. 8 minutes for firmly hard boiled.
As an egg ages, this air cell grows larger as the yolk and white further contract. Therefore, an older egg is less dense and more likely to float in boiling water. Store-bought eggs can last several weeks beyond their sell-by date or expiration date. To reduce the chances of eggs going bad, keep them refrigerated.
If your egg has broken into the boiling water, you should find strings formed from the leaked egg white into the water or clumps of the white on the egg shell. But, don't worry, the egg is still safe to eat as long as you hard boil them.
Bacteria can enter eggs through cracks in the shell. Never purchase cracked eggs. However, if eggs crack on the way home from the store, break them into a clean container, cover tightly, keep refrigerated, and use within two days. If eggs crack during hard cooking, they are safe.
However, since the inner membrane clings tightly to the shell of a fresh egg, it's near-impossible to have anything but ugly results when you try to hard-boil them.
Most of the time it's the result of extreme temperature changes ie fridge to boiling water or worse boiling water + salt (higher temperature). Take eggs from fridge and warm them under hot tap. Submerge eggs at least 1 inch below in non salted boiling water.
You might have heard that you should drop your eggs into room temperature or cold water and then bring the water to a boil. This is a myth. In our tests, bringing the water to a boil first and then lowering the eggs into the bath made for easy peeling and more accurate timing.
Just a teaspoon of salt can efficiently prevent the eggs from cracking during the boiling process. Fill a pot with water, put on the heat and mix 1 tsp salt in it. When it comes to a boil, gently drop the eggs into the pot and boil them for 10 minutes to get the perfectly cooked yolk.
The ice bath will cool the eggs quickly and stop the cooking process. The ice water will also cause the egg to contract and pull away from the shell, which will make it easier to peel. Let the eggs sit in the ice bath for at least 5 minutes.
Add salt and vinegar to the water.
The salt permeates the shell a little bit, and the vinegar helps to break down the shells, making them easier to peel.
The vinegar in the water makes the eggs easier to peel. Here's why: The vinegar's acid not only dissolves some of the calcium carbonate in the shell, it also helps the whites set faster. Running the hard-boiled eggs under cold running water as you're peeling, meanwhile, helps the shell separate from the membrane.
Starting eggs in cold water greatly increases the chances of shell-sticking. Even with two-week-old eggs, starting cold resulted in eggs that had just over a 50% success rate for clean peeling. Eggs started in boiling water or steam came out well above 90%.
Tips for Perfect Hard Boiled Eggs:
Don't cover with the lid or you won't be able to see when the water starts boiling. Set a timer as soon as the water is at a boil (keep watch for the start of the boil so you aren't guessing at your timings).
An ice bath stops the eggs from continuing to cook
And as anyone who's ever overcooked an egg (which is probably everyone) knows, it doesn't take long to go from perfectly set egg whites and beautifully yellow yolks to rubbery egg whites and a chalky green-tinged yolk with a rotten egg smell.
Why are fresh eggs so hard to peel? The fresher the eggs, the harder they are to peel. This is because the egg white or “albumen” in a fresh egg has a relatively low pH level, making it acidic. When cooked, these fresh egg whites bond strongly to the inner shell's membrane.
If you boil an egg for five or 10 minutes, it becomes firm and cooked. If you boil it for hours, it becomes rubbery and overcooked.
Apparently super fresh eggs are difficult to peel because the pH of the white is more acidic which causes it to adhere to the shell membrane more tightly. Two solutions here – use older eggs or add a little bicarb soda to the cooking water to increase the pH.
Boil for 6 – 7 minutes over medium-high heat for perfect hard-boiled eggs. Using a slotted spoon, transfer them to a large bowl of ice water and let them cool for a few minutes. Or you can place them under cool running water to stop the cooking.
However, if you cook one egg in a pot of boiling water for 20 minutes, the increased time will cause the moisture in the egg to expel. The egg white will clump together tightly, and the yolk will develop a greenish film over a chalky center. As a result, you'll have a bouncy and tasteless hard-boiled egg.