i have made and bought many incubators over the years and had many successful hatches and a few not so successful. Re humidity levels, in a still air incubator in some areas of the country, particularly the more humid areas you can get away running dry or almost dry till last 3 days. The last three days it is critical that humidity remains high, typically 70% or above. I read here where one person had staggered hatch dates in same incubator. My strongest recommendation is to have a seperate hatcher set up for several reasons.
#1 hatching is messy and with high humidity, moving all that air around in a incubator with other eggs in earlier stages of develpoment can potentially spread bacterior from already hatched chicks which could contaminate those earlier stage eggs.
#2 its not at all good to be raising the humidity to lockdown levels while you have earlier stage developing eggs, you might well set them up to drown.
#3 Opening and closing the bator to remove hatched chicks in staggered batches will effectively remove the humidity level that you worked so hard to acheive so the hatching chicks don't dry out and get stuck.
We call it lockdown because it should be just that, don't open the bator under any but emergency circumstances durring the entire hatch.
A side note for all who wan't to raise humidity and are having trouble doing that............ Take a new clean synthetic sponge like you would use to wash a car, lay it flat on its side and cut "v" notches across its surface to a depth of about 2/3 of the sponge depth and open about 1/2" to 3/4"wide at the notch top, (you can cut several on the same sponge side by side) each notch increases the sponge surface area and will put more moisture into the air.
I recommend placing this sponge in a container that is stable (not likely to tip) and that is not more than 1/2 inch larger than the sponge.you can cut the sponge to fit a container easier than finding a perfect sized container.
Fill the container with incubator temperature water and place it directly under or in front of the fan in the case of a fan style bator.
The stability is necessary so chicks that hatch don't spill it.
The fairly tight fit of the sponge is so chicks can't get into it and drown.
You can experiment with diffrent #'s of notches to adjust for higher or lower humidity. Of course its best to experiment and know how this all works before setting eggs.
You really don't need to add more sponges, just more surface area to the sponge you have.Try to place sponge where it gets fan assist in evaporation, and where you can refill the dish thru a tube without opening the bator.
Remember to always use water approx the temp of the bator air otherwise you risk chilling or overheating the bator air. Its a good thing to note that evaporation process cools air so watch and adjust temp if necessary,
One last comment, chicks that have made it part way chipping around the egg and stop for more than a day but are still alive often are stuck because they are dried to the interior of the egg. What i am about to suggest is an extreme but it has worked for me several times. if you can see the chicks beak, carefully pick the hole in its beak area open a bit more. the chick breathes thru its mouth and nose, so if your sure its an issue of dry stuck chick, you can carefully add moisture using an eye dropper in the form of bator temp water into the egg being careful not to drown the chick.
If you add enough moisture you may be able to rewet the chicks stuck feathers and free it. if you think you have wet the feathers enough to free the chick, carefully turn the egg and evacuate the majority of the water and place the chick back into a high humidity hatcher and pray. I only recommend the above proceedure in extreme cases where you don't want to lose an expensive chick...NOTE sometimes it works, sometimes it does not, i just wanted to give you another possible tool in your arsenal to combat hatch failure. I hope i have been a help to some of you. happy hatching.....Tom
