What is an Egg Float Test?

An egg float test will help you determine the remaining air inside an egg.  Eggs of uncertain age can be tested to see if they are still fresh.  Remember, not every egg that floats is bad, but it is no longer fresh.

What is an Egg Float Test?
By Pierre Mouchette | Bits-n-Pieces

An egg float test is a simple way to check the age of an egg.  All eggs have an air cell, and as the egg ages, the air cell becomes bigger.  When an egg reaches the right age, and the air cell is large enough, the egg becomes buoyant.  Air in the compartment acts as a life preserver and keeps the egg afloat.  It is important to remember that the egg float test is a method to check the age of an egg.  
Old eggs are still usable, but the use-by date on eggs is essential to monitor and act upon.  If you have completed an egg float test and think an egg is old, you could still crack it open and check for a rotten egg odor.  If it smells bad, it is bad.  It is worth noting that the smell of a rotten egg is powerful.  If you discover an egg that floats and wish to test it, go outdoors to crack it open so you can easily discard it without letting the odor escape in your home.
If you raise chickens, you may have noticed that fresh eggs are delicious, both scrambled and fried but are hard to peel when boiled.  There are several techniques to make it easier to peel a fresh egg.  For example, do not boil, but steam the eggs for 20 to 25 minutes. Stabilizing the egg white and also letting the egg age can help.
 
How to do the egg float test?
Use a bowl of cool water that is egg deep plus a few inches.  Carefully place the egg in the water.  If it floats, it is old enough that it can be suspect.  If it bobs to the surface quickly, remove it from your home.  Do not break the shell. 
Newly laid eggs have an exterior coating that protects their contents.  Even if your egg does not float, you have shortened its shelf-life by getting it wet and washing away the protective layer.  Some people advocate spinning the egg to check for freshness.  This technique is less reliable than the egg float test and increases the risk of cracking.
 
Which End is Up?
The air pocket in an egg will often flip to one end or the other when you put it in the water for the egg float test.  If your egg floats the long way, it is older and should be used immediately.  It is probably a good candidate for boiling or steaming.
Eggs can still be good even if they have sat out in the elements for a time.  While it is essential to use the guidance of "use by dates” labeled on your food, unfertilized eggs laid by a chicken on the free-range grounds can sit for days before they are picked up and can still be viable.  Do not be afraid to gather them and test them for freshness.
 
Risks of Eating Old Eggs
The egg float test can be used on store-bought and farm-fresh eggs.  Use the test if eggs from the store are close to the use-by date stamped on the carton.  If they float, they are old and could be spoiled.  Before purchasing eggs at your local grocery store, eye the carton for breaks.  A cracked egg can become a breeding ground for a range of bacteria.  
Salmonella contamination (salmonellosis) is a common bacterial disease that affects the intestinal tract and is the most common cause of eating undercooked or old eggs.  You are likely to suffer fever, diarrhea, and vomiting from it.  If it is severe, you may suffer organ failure and death.  Not all eggs contain salmonella, but anybody who eats undercooked eggs is at risk.
 
If your eggs are within the use-by date, but you notice:

• odor
• slime
• powder film (mold)
• breaks in the shell

 
Get rid of them.  It is always safest to toss the container and buy another dozen.  Carefully inspect all eggs in the carton when you purchase them.  Also, examine the lower part of the carton for moisture.  Cracked eggs leak and contaminate the container!