Originally Posted by groundpecker
From my personal hatching experience, high humidity only drowns chicks if the humidity is high the first 18 days. 3 days of high humidity during lockdown should not drown the chicks. Matter of fact, the last hatch i had 6 of 8 eggs to hatch and humidity was over 80% during lockdown. I would not worry about it, unless your humidity was high during the first 18 days.
Edited by Gypsy07 - 11/5/11 at 6:02am
Yup, this is exactly correct. I usually lockdown and hatch at 75-80%, and have occasionally had hatches get as high as 90% without any problems.
If your egg has lost the correct amount of moisture by day 18, it won't regain that moisture during lockdown. That just doesn't happen.
If your egg hasn't lost enough moisture, your chick will most likely still be alive. It physically can't drown until it tries to start breathing air, it doesn't start breathing air until it breaks through the membrane into the air cell, and this won't happen until lockdown. At this point, if there is too much moisture still in your egg, the chick will inhale the moisture and drown. Because the drowning happens during lockdown, people get confused and blame it on a too-high lockdown humidity, when actually the real culprit is a too-high humidity throughout the first 18 days of the incubation.
If you're having problems with figuring out humidity and moisture loss, get yourself a cheap digital kitchen scale and start weighing your eggs. Chicken eggs should lose 13% of their starting weight by day 18, and with a set of scales, you can ensure that this happens. No more humidity problems, as you can check on moisture loss throughout the incubation and adjust your humidity up or down as required to make sure that your eggs lose the correct amount of moisture. No more guessing. No more worrying. It really is that simple and I can thoroughly recommend it.