Quote:
I just went back and checked out that thread.
Have a look at Jamie's post, #255, in the middle of the page:
https://www.backyardchickens.com/forum/viewtopic.php?id=113681&p=26
That's exactly how I've been doing it, with the exception of during days 1-18, I'll push the envelope a bit further on each end, depending on how the weight loss is going. For the hatching phase, I keep it at 58-60% RH. It will rise a little as peeps start hatching and I've had it go to like 62.
My understanding is that the big danger of peeps drowning comes from the eggs not having lost enough weight during the setting phase, so when the peep pips into the air cell, it drowns in the excess fluid.
I have not read anything about the Marans egg shells and membranes being thicker and needing higher humidity for the hatch, but I do believe that they are perhaps not as porous (they're clogged with that "Marans paint"?) as other shells and thus need more "persuasion" during the setting phase to ensure adequate weight loss. Case in point, my last hatch was 7 BC Marans and 9 Olive Eggers...the Marans had only lost like 9+% while the OEs had lost 12+% on average. These eggs all came from the same breeder at the same time. Although the Marans eggs had fallen short of the target of 12-14% weight loss, everybody hatched. And they hatched with gusto, a day early.
I think it's important to make a distinction between the two different phases...setting and hatching. During the setting phase, the goal is to achieve that weight loss, thereby ensuring that the air cells are large enough. Then, during the hatching phase, the goal is simply to keep the membranes soft and pliable by boosting humidity. That's how it works in my head at least.
Clear as mud?