Use three liang of salt dissolved in a small basin of water. Place the egg in the saltwater. An egg laid three days ago will sink to the water slightly off the bottom of the basin. If it was laid more than five days ago, it will float on the surface. Another method is to place the egg in clear water. An egg that is fresh will point downwards; if not, it is old.
How to tell if an egg is good or bad?
(1) The Appearance Method
The shell of a fresh egg has a layer of frosty powder and is not very smooth to the touch. A smooth, dull shell indicates an old egg.
(2) The Shake Method
Hold the egg and shake it. An egg that makes no sound is fresh. An egg that makes a sloshing sound is bad. The louder the sound, the worse the egg is.
(3) The Candling Method
Hold the egg gently and observe it against a light source. A good egg has a clear, translucent albumen with a small air chamber at one end. A bad egg appears grayish and has a larger air chamber.