How to... Test for Freshness

Egg shells are porous; designed to let in air so that the chick inside can breathe. The small air pocket between the egg membrane and the shell increases in size as the egg ages. This air pocket can provide a useful means of testing for freshness. To test, put the egg in a glass of water: if it lies horizontally on the bottom, it is fresh. If it floats vertically, this shows that the air pocket has grown and the egg may well be stale. When cracked, a fresh egg will have a rounded yolk sitting in a gelatinous white that has a thinner rim of white around its edge. A staler egg will have a flatter yolk and a runny white.