The air cell extends most of the length of the egg. ... The essence of the float test is that newly laid eggs will lay flat on the bottom of a glass of water and very old eggs will float to the top. I would like to emphasize that the float test does NOT reveal whether an egg is spoiled, rotten, contaminated or bad.

Does a fertile egg float or sink?

If eggs sink to the bottom of a bowl of cold water and lie flat on their sides, they are very fresh. If they are less fresh but still good to eat, they will stand on one end at the bottom. If they float to the surface, they are no longer fresh enough to eat.

Do fertilized eggs float in water?

Gently place the egg in the water. If it floats, it's old enough that it may be suspect. ... Candling eggs is the best way to determine if an egg has been fertilized. Don't rely on the float test and crack open a fertilized egg.