Quote: I'm sorry I can't explain the science very well, but the point behind lowering the temp is that at that high a humidity the oxygen level is decreased sufficiently to kill chicks. BY decreasing the temps little, the air can resaturate to a more normal level. Remeber at hatch time the chicks are making thier own heat. ONly those still developing need the warm heat to keep developing; otherwise hatched chicks are good under a heat lamp of 95 . . . . SO a hatching temp of 98.5 should be fine.
Sounds like you explained the science pretty well!
I have to admit I'm getting confused by the term hatcher vs incubator. I thought chicks/poults hatched in the incubator then went into the brooder. Did I miss a box? Or are you using the term hatcher to refer to the last few days of incubation when you raise the humidity and stop turning the eggs, which I've heard described as lockdown?
I am venturing into hatching for the first time, and the eggs are on day four of incubation. I have one broody (chicken) hen setting on her own five eggs, plus 11 eggs in the incubator from two other hens that will be separated in pedigree cages at lockdown. The incubator eggs were started about 18 hours after the broody eggs, and my original plan was to let everyone hatch, leg band everyone to keep track of parentage, then slip the incubator chicks under the broody hen on the first night. But now I have a second broody hen, so it looks like I'll be able to let her continue her brood over ceramic eggs, then distribute the chicks evenly after they're banded, assuming that there's enough viable eggs to justify having two broodies when they're candled. If not, I'll break the brood of the second broody early.
Some people do use a second incubator for lockdown. It frees up the main incubator for hatching more eggs right away.