Why eggs crack when boiling

Cracking is caused by trapped air expanding and by eggs knocking together. Four fixes that work, and one popular one that does not.

Every egg has an air pocket at the fat end. Heat it and the air expands, pressure builds, and the shell gives way at its weakest point. That is most cracks.

The rest come from eggs knocking against each other and against the base of the pan once the water is moving.

What actually works

Lower them in gently

Use a slotted spoon and put them on the bottom rather than dropping them. Most cracks happen in the first two seconds, from impact, not from heat.

Turn the boil down once they are in

You want the water moving but not violently. A hard rolling boil bounces eggs off each other and off the pan. Reduce it to a gentle boil after the eggs go in and the timing barely changes.

Do not crowd the pan

One layer, with room between them. Eggs stacked on top of each other crack the ones underneath.

Let very cold eggs sit for a few minutes

Thermal shock genuinely matters at the extremes. An egg at 4 °C going into water at 100 °C is a 96 degree jump. Ten minutes on the counter takes the edge off it. Fewer cracks, and the calculator has a room temperature setting so your timing stays right.

Pricking the shell

The advice is to pierce the fat end with a pin so the expanding air escapes. It does work, and it is what egg pricker gadgets are sold for.

It also puts a hole in the shell. If you go too deep you pierce the membrane and white leaks out, which is worse than the crack you were preventing. Most people who try it once go back to lowering eggs in carefully.

When one cracks anyway

Add a splash of vinegar to the water. It makes leaking white set faster, so you get a small tidy plume instead of a pan full of wisps. It will not repair the shell.

A cracked egg is still perfectly safe to eat. It just looks untidy and the white can be slightly watery where it escaped.

Other boiling times

Egg guides

Common questions