Quote: I have never had an egg dry out.
I live in Wisconsin and we have pretty high humidity. Right now my bator reads 35% without any water in it. If it drops below 20% I do drop a moist papertowel (wadded up) in one of the shot glasses. Chicks use the moisture inside to grow and develope. As they develope they loose moisture and the air cells grow larger. The dryer humidity get the egg ready to hatch for the first 18 days, the last days of moisture helps the chick break the egg and move. Too much moisture and you might have absorption issues, belly botton issues, leg issues, swollen bellys,.infections etc.all that moisture stuffed in an egg..if you think about it logically it is funny that more chicks do not have infection issues..dryer hatches just mimic the hen better if you live in a damper climate. It might not work for everyone. Each climate is different. For me, dry hatch works best.