Is the egg float test accurate? What a floating egg really tells you

A bowl of water and one egg that will not sink

It's Saturday morning. You have eggs from the store and a carton from a neighbor's hens. You can't remember which are which, or how long some have been in the fridge.

So you do what your grandmother did. You fill a bowl with cold water and set the eggs in one by one. Most sink. One stands on end. One floats.

The floater goes toward the trash. Then you stop. Is it really bad? Or did you just throw away a good egg?

And if the sinkers are "good," does that mean they are safe?

Why the float test answers the wrong question

The float test is real. It just measures something other than what most people think.

Every egg has a small air cell inside. As the egg ages, that air cell grows. When the cell is big enough, the egg floats. FSIS explains that an egg floats when "its air cell has enlarged sufficiently to keep it buoyant."

So a floater is old. FSIS goes on: it "is of poor quality, but it may be perfectly safe to use."

The sinkers have the opposite problem. They pass the test, so they feel safe. But age and safety are two separate things. A fresh egg can still carry germs.

The check that actually works

Keep the bowl of water. Use it to sort fresh from old. Then add one step.

Crack each doubtful egg into a small, separate bowl before it goes into anything else. Look at it and smell it. FSIS says to "examine it for an off-odor or unusual appearance before deciding to use or discard it." If it smells bad or looks odd, throw it out. FSIS says a spoiled egg "will have an unpleasant odor when you break open the shell."

That handles spoilage. It does not handle Salmonella, and nothing at home can. FSIS says germs that cause illness "do not generally affect the taste, smell, or appearance of a food."

So the last step is in the pan. The FDA says to "cook eggs until yolks are firm." Cook every egg until the yolk and the white are both firm. The FSIS page on shell eggs has the full storage chart.

Clean, uncracked eggs can still carry germs

This one surprises many people. A perfect-looking egg, clean and whole, can have Salmonella inside.

Our grandparents believed the inside of an egg was sterile. Utah State University Extension describes the old belief: "It was thought that eggs were sterile inside the hen." Research proved otherwise. Salmonella enteritidis "can contaminate eggs as they are formed inside the hen's reproductive organs."

That is also why the old water-glass crock is retired. A coating on the outside can't stop a germ that is already inside. Utah State says plainly: "do not use water glassing for egg storage." Freeze extra eggs instead, mixed with a little salt or sugar.

Keeping store eggs the American way

US store eggs are washed. That is why they belong in the fridge from the store to the pan.

Keep them in their carton on a fridge shelf, not in the door, at 40°F or below. Use raw eggs in the shell within 3 to 5 weeks. Don't wash store eggs at home, and don't leave them out more than 2 hours. FSIS explains that a cold egg left out "can sweat, facilitating the movement of bacteria into the egg."

Backyard eggs from a small flock are a separate question. The book does not cover washing farm-fresh eggs and sends you to your county extension office for those.

Where the book covers eggs

This is the problem The Lost Kitchen Skills, Checked was written for. Nancy Whitaker checks 42 old kitchen skills against current guidance and gives each a badge.

Eggs: Keeping, Testing and Preserving has three cards. Store Eggs the American Way and The Float Test, Checked are both badged UPDATE IT. Freeze Extra Eggs Instead of Water-Glassing is one of the book's four RETIRED skills, with the freezing steps that replace it. A side-by-side table shows Grandma's way and today's way for storing, testing, keeping extras and washing.

The chapter's myth check tests three claims: that the float test shows safety, that clean eggs can't have Salmonella, and that washing store eggs makes them safer.

If you like checking the old habits, our page on cooling a big pot of stock looks at another one, the pot left on the stove overnight.