Why do the eggs grow to day 18 and then not hatch?

[BullChick]

Concentrating on humidity (a dirty incubator, and faulty parents are also possibilities), I have questions!

Did you calibrate your equipment before each hatch?
Are you rotating the position of the eggs in the incubator?
Are the eggs old?
Are you shorter than 5’8”?
Are you laughing at the last question?
Is the room unstable? Hot then cold, or humid then dry (storms coming through can hurt hatch rates)?

 

[BullChick]

Old eggs are more like two weeks, not one.
Dirty hands can introduce bacteria.

There will always be two sides to a problem. I’m unfamiliar with the mentioned study.

 

[rjohns39]

I've had my best success with the set em and forget em approach. I typically use 99.8* and 40% humidity until lock down and then bump it up to 65%. I can't set eggs until after 4/15 as room temps fluctuate too much.

 

[NomoreCSIncubating]

The got over heated in the egg and stopped! Some chicks can stand some heat but not all..

One thing to remember a hen can never over heat an egg so they are designed to hatch at a certain temp to hot and it is unhealthy for them.

 

[NomoreCSIncubating]

Some of the air cells look small.
View attachment 1752607

The size of the aircell has nothing to do with the ability of how an egg hatches out and since chicks grow at different rates the air cell will never be a consistent size.

There is only one reason for a large loss on the last 3 days and that is it got to hot inside the egg.

 

[BullChick]

Or they couldn’t breathe.