I am not exactly sure on how accurate my hydrometer is with my humidity either. It is a few years old maybe 4-5. It came with my incubator and I haven't ever calibrated it either. Who knows it might be right or wrong. I might borrow one from someone to see if it is right. During the spring the...
This technique is actually called "Dry Incubation" not dry hatch. meaning little to no water is added while incubation and then on day 18 the humidity is increased in order for the chicks to hatch. It is as simple as what ever the humidity is when there in the room you are incubating is no water...
I have my hatcher around 30% humidity and chicks hatch fine. During hatching I do not open the door for at least 2 days or until all of the chicks are hatched.
Nate
I use Dry Incubation and it works great! I don't have to worry about having a certain humidity in my incubator it stays around 16-18% and then in my hatcher I have the humidity around 25-27%. I haven't had hardly any problems with the chicks hatching!
Nate