some of this will depend on the humidity outside and the humidity inside your home.. I e different settings for the dessert and rain forest..but as a general rule you can be lower than 40% for the first 18 days and do better than if you are higher. if you remain too high the 1st 18 days some or all of the eggs will not lose enough water and the air sac will be small causing the chicks to drown before they can get out of the shell. if you are too low some or all may lose too much water and the chick will be so dry he gets stuck to the membrane and cannot zip around and get out of the shell there is a thread on here about dry hatching ...it is an interesting read but remember anyone can post on here with or without research and facts to back up what they say. let the buyer beware ..you will have to tinker with the settings for your home . my friend hatched some eggs for me last year her 1st hatch she hatched 35 of 35 eggs.. the next few hatches not that high but an acceptable 80% or so. she lives 40 miles from me and the humidity is a little different than at my house.. in my opinion it is safer to start with a little lower humidity and go up if your hatch isn't as good as you want. that is where I have had better results your may be different so have fun and experiment happy hatching
Good post.
I have an older model of the 1588. It has 5 different reservoirs in the tray in the bottom. If I don’t put any water in it, the humidity might read 15% or 35%, depending on the time of year, whether the air conditioner or heat is on or not, and the outside conditions. Filling one of the middle trays might give me 30% to 45%. That’s with it in the same position in the same room. Sometimes during the incubation phase I might have it empty, fill one reservoir, or fill two. During lockdown I usually fill two but occasionally three.
The instantaneous humidity during incubation isn’t all that important. The average humidity is what counts. As Ronniewayne said, it’s about how much moisture the egg loses during the entire incubation, not how much it is losing at any one point in time. It doesn’t hurt for it to be low for a while then high for a while as long as the average is about right.
Something else is that different humidities inside the incubator work best for different ones of us. The commercial hatcheries, where they might hatch 1,000,000 chicks a week using incubators that hold maybe 60,000 eggs each, find that if they move one of those incubators to a different place in the incubation room they have to tweak the settings to get the best hatches. You’d think that the conditions inside the incubator would be the same, but it’s not. For example, the temperature and moisture content of the air being drawn in affects how fast the eggs dry out. The good news in this is that there is a fairly wide range in humidity that works pretty well for us. You don’t have to be dead on exact to get a good hatch. But obviously you want to be as close as you reasonably can to your unique conditions.
For your first time, I suggest you try to keep the humidity at a certain level as well as you can during incubation. That’s not always real easy. Then open any unhatched eggs and try to determine what went wrong. There are a lot of things that can go wrong other than humidity, but humidity is important. If your humidity is bouncing all over the place how do you know what to adjust?
