Putting them in water is a time-tested way to check if an egg is good or bad – if it sinks, it's good; if it floats it's bad. It's just not a reliable method.

We had a floater recently and it was fine.

Floating is an indication that the egg is fairly old. A very fresh should sit on the bottom of a pan of water. As it gets older, it begins to stand on its pointy end, and eventually an egg may float to the surface.

When the egg is laid, it may very well not even have an air pocket inside the large end of the shell – that is, the shell may fit perfectly. Over time, moisture and carbon dioxide are lost from the white and exit through the pores of the shell, to be replaced by air coming into the shell. As the air pocket gets bigger, the egg becomes more buoyant.

Break a questionable egg into a dish, and smell it and look at it before you decide whether to use it or toss it. A spoiled egg – raw or cooked – will have an unpleasant odor and you will know right away whether it's good or bad.

Now that we have taken away the only method you had for determining if an egg is bad, you'll understand why some cooks break eggs separately into a dish before adding them to the other ingredients of a recipe. That way they only have to throw out one bad egg and not the entire mixture. The incidence of bad eggs is so rare, however, that most people get cocky and ignore that practice.