So I felt the need to post this here. A little backstory, my 2 sisters are allergic to CHICKEN eggs but not duck eggs. They'd been ordering fresh duck eggs for about 2 years and receiving floaters sometimes and I had told them the trick of if it sinks is good, if sinks but stands underwater is ok fully cooked by it floats toss it bc its rotten.
For years this is what I preached, until pre pandemic I had the genius idea that "rather than pay $40 x duck egg delivery let's buy ducks instead , I purchased and raised Golden 400s 9 hens and 1 drake, and they were consistently laying eggs on the daily, sooo many eggs. And to my surprise I too had a few floaters, I was baffled. So I figured maybe it was the drakes fault bc maybe he was fertilizing then and making them go bad, so I got rid of him and kept only females, months passed and I was STILL getting floaters
so that's when I started wondering what was going on....
Turns out the only thing the float test tells you, is how FRESH the egg is... the air pocket as with all eggs increased over time as the egg ages, but it's no clear indication that the egg itself is rotten or not..and this makes sense... I've had even sinkers that are stinkers in both chicken and duck eggs, and during the winter my ducks don't lay as much, same as hens, sooo that said, nothing can tell you if an egg is spoiled besides checking the smell, color, with your physical nose and eyes.
I had my sister break open a bunch of the floaters duck eggs and all looked beautiful and smelled fresh and clean... sooo.. yeah weird.
Regardless I'd still recommend cooking floaters 100% of the way through to err on the side of caution... oh and I also found this article to back up my theory/ findings
https://www.healthline.com/nutrition/tell-if-eggs-are-bad
For years this is what I preached, until pre pandemic I had the genius idea that "rather than pay $40 x duck egg delivery let's buy ducks instead , I purchased and raised Golden 400s 9 hens and 1 drake, and they were consistently laying eggs on the daily, sooo many eggs. And to my surprise I too had a few floaters, I was baffled. So I figured maybe it was the drakes fault bc maybe he was fertilizing then and making them go bad, so I got rid of him and kept only females, months passed and I was STILL getting floaters

Turns out the only thing the float test tells you, is how FRESH the egg is... the air pocket as with all eggs increased over time as the egg ages, but it's no clear indication that the egg itself is rotten or not..and this makes sense... I've had even sinkers that are stinkers in both chicken and duck eggs, and during the winter my ducks don't lay as much, same as hens, sooo that said, nothing can tell you if an egg is spoiled besides checking the smell, color, with your physical nose and eyes.
I had my sister break open a bunch of the floaters duck eggs and all looked beautiful and smelled fresh and clean... sooo.. yeah weird.
Regardless I'd still recommend cooking floaters 100% of the way through to err on the side of caution... oh and I also found this article to back up my theory/ findings
https://www.healthline.com/nutrition/tell-if-eggs-are-bad