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Originally Posted by
Apriljc 
Hi there. A couple questions for you.
I read that a day or two before the chicks break the membrane, the membrane draws down and anywhere from a day to three days after the membrane is broken, the chick pips and emerges. My question is, does this all begin around day 18 so that they emerge around day 21? Or does the process START around day 21? Will I see these changes when I do my final candling on day 18?
Keep in mind that we are speaking in generalities here because depending on a number of variables the timetable can run a little fast or slow. At about day eighteen the chick begins to position itself to begin the hatching process. It will internally pip meaning it breaks into the air cell then may likely rest a bit before it begins to work on breaking through the shell itself. The average chick in average conditions will typically fully hatch on the twenty first day.
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And, I assume they naturally position themselves to break the membrane. Does having the airspace turned toward the bottom of the egg or toward the top at lock-down, matter?
Yes, having the airspace properly positioned matters. Sometimes a chick will pip the wrong end of the shell. Sometimes the will successfully hatch anyway, sometimes they won't. Usually though they know to position themselves towards the fat end of the egg where the air cell should be and those are the ones with the greatest chance of successfully hatching.
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Lastly, does high humidity need to occur before they break the inner membrane or is it okay to wait till they pip? I ask because it was suggested to me to delay increasing humidity since the air spaces aren't very big. I'm having a hard time getting the humidity down in the incubator to encourage some evaporation because the weather has been so hot and humid lately.
Today is day 16. ( I candled this morning and the air spaces are a tiny bit bigger than my pencil line from two days ago).
That's a tough one. Ideally you would want to bump the humidity the last three days to soften the shell membranes to make it easier for the chicks to hatch. But if you've been running high the entire time I believe I would not increase it at this stage as you are already at risk of having some drown in the shell or at least hatching very sticky.
Do you know exactly what your humidity is right now and are you using a calibrated hygrometer or wet/dry thermometer?
