What incubator do you have, make and model? Forced air or still air? That might help us a bit.
Have you checked your hygrometer to make sure it is working right? Thermometers and hygrometers are notorious for not working right and messing up hatches. You may need new instruments.
Rebel’s Thermometer Calibration
http://cmfarm.us/ThermometerCalibration.html
Rebel’s Hygrometer Calibration
http://cmfarm.us/HygrometerCalibration.html
During the first week or so it doesn’t matter, but after that the eggs need an exchange of air. The egg shells are porous and the chick inside is breathing so it needs to get rid of the bad air and get new good oxygen-filled air. The later in the incubation the more those vents need to be open. That’s more important in a still air than a forced air but I’d still want at least one vent open. Lack of oxygen is one reason some eggs can go to full term or even hatch and then die. They suffocate. The more vents are open the more humidity escapes.
The temperature and humidity of the air going in has a big effect on the humidity of the air inside the incubator. What environment is the incubator in? Is it inside an air conditioned house where you are wringing the moisture out of the air? Maybe you are heating with wood and the air is extremely dry? The incubator should not be in the draft created by a vent and the temperature should be pretty stable around it.
Don’t believe them when they start putting numbers to what humidity you should have with certain water reservoirs filled. You have to determine that for yourself. Just moving the incubator from one side of the room to another can make a big difference. I can have a difference of 15% in the humidity inside mine depending in the time of year and the conditions of the air going in. That’s with the incubator in the same place, temperatures stable, and no draft from vents.
In most incubators the way you control humidity is the surface area of the water. If your instruments are working properly then you can try adding more reservoirs in there somewhere. Or put sponges or towels in there with a corner in a reservoir so it will wick moisture out and give more area for water to evaporate. That will drain that reservoir faster so watch out that it doesn’t go dry. That’s the main purpose of my hygrometer. When humidity starts to drop it’s time to add more water.
Something else to check. Is your lid on correctly? One time the cord to my turner was not in the channel for it and it was cracking the lid open. That came close to driving me nuts trying to figure out why the humidity was so low.
Good luck!
