What an Eggshell Tells You

Lower the egg into a glass of cold water and watch how it settles. What you are measuring is how much air has worked in through the pores since it was laid — in other words, its age.

Floating does not mean rotten. A well-kept egg ages, floats and is still perfectly edible. And the reverse: salmonella contamination does not produce enough gas to lift an egg, so a dangerous egg can sink without giving anything away.

The popular shorthand — "it floats, it is off" — makes people throw out good eggs and trust bad ones. For a test, that is the worst possible combination.

Lying flat on the bottom: very fresh, a few days old. This is the one you want to poach.

Tilted, blunt end up: a couple of weeks. Fine for anything.

Standing on end on the bottom: old, but usually still good. The best candidate for hard-boiling.

Floating: quite old. Do not bin it: crack it into a separate bowl and smell it.

There is only one way to find out whether an egg has gone bad: open it. A rotten egg announces itself with an unmistakable sulphurous smell that leaves no room for doubt.

That is why you crack it into a separate bowl before it joins anything else. A single bad egg ruins the dozen, the cake and the afternoon, and once it is in there is no way back.

An egg comes with a natural coating that seals the pores, the cuticle or bloom. Washing it off with water lets surface bacteria in where they could not get before.

This is where countries part ways. In the UK and the EU, washing eggs for retail sale is prohibited, and eggs are sold and kept at room temperature. In the United States eggs are washed as a matter of regulation, and precisely because of that refrigeration is required. Both systems are coherent; they just start from opposite ends.

If an egg arrives dirty, clean it dry: a paper towel, a cloth, or gently rubbing it. That is exactly the egg that most needs to keep its cuticle.

And if washing is unavoidable, the water must be warmer than the egg — so the contents expand and push outward rather than drawing inward — and use it straight away rather than returning it to storage.

It depends on whether they were washed, which is why the answer changes with where you live. In the UK and Europe, with the cuticle intact, eggs keep well on the worktop. In the United States, where they arrive washed, they must stay refrigerated.

⚠️ Either way it is a one-way decision. An egg that has been chilled and comes back to room temperature sweats on the outside, and that film of water carries bacteria inward through the pores. Once it goes in the fridge, it stays there.

And because of the same porosity: do not store them next to anything strongly scented. An egg takes up garlic, onion and fish through the shell, and that smell turns up later in the omelette.

On a flat surface, not on the rim of a bowl. The rim drives shell splinters and whatever is on the outside into the egg; a short tap on the worktop opens a clean crack.

And always into a separate container, for the reason above: cracking straight over the mixture is the habit that ruins everything one day.

One drop of yolk and the whites will not whip. Yolk is fat, and fat stops the white proteins from forming the network that traps air.

So separate each white into a small bowl and only then add it to the rest. If the fourth one goes wrong you lose one white, not four.

And avoid plastic bowls: they hold a film of grease that washing up does not remove, and that film is enough to ruin the whole thing. Metal or glass, thoroughly dry.

Age matters here too: the white of a fresh egg is thick and whips to a firmer foam, while an older white is looser, rises faster and collapses sooner.