Quote: First three weeks I dry incubate = add just enough water to keep humidity 30-40%. It fluctuates. THe key is to follow the air cell development = matches diagrams on days 7, 14, 21 and 26.
If at lockdown the aircell is the correct size, then I bump up the humidity to 80%, and temp needs to decrease a degree. THis is Porter's method.
But as I have said, I have many chicks/poults hatch while still in the incubator at the lower humidity.
In general I think that the higher humidity helps keep the membrane moist while a poult is slow to zip. To keep that membrane from getting too dry. On the other hand I have seen it be too wet and it became rubbery and the chick still couldn't get the lid off. IDK? THis is why I help. I can always cull later if there was a physical anomoly.