I'm living in the dark ages and I don't have a hygrometer "yet". I'm going to look for one tomorrow at our feed store but I have a feeling I'll have to go to Springfield or order online. I have a styrofoam incubator, still air. I kept the temp at 100 on the bottom. I filled the main ring with water for the entire time then added 2 soppy wet wash cloths the last couple of days. I did help them after they had been pipped more than 8 hours. I chipped the shell off all the way around exposing the white membrane and kept it damp and laid the egg on the damp cloth. After a few hours, they were still active and cheeping and I carefully snipped the membrane, no bleeding so I used clean tweezers and took a couple of strips of the membrane off. I did this before they were worn out from trying to get out so they were very quick to kick their way out and were up and running all over pretty quickly. They are very robust chicks and I attribute that to good breeding (Jerry's Serama's) plus the hens and rooster had excellent nutrition. I provided the usual ration of all they can eat laying mash with greens on the side, finely crushed oyster shell calcium with parakeet grit and gravel free choice and usually I added some wild bird seed that had millet and shelled sunflower seeds in it ....plus whole flax seeds and occasionally they got crushed probiotic capsules like you get at any pharmacy for people. I had wormed them with piperzine before I started saving eggs too. I think if you prepare the hens and rooster with excellent nutrition, the ones that do hatch will be stronger, healthier chicks
Mine wasn't a really big hatch but I'm really pleased with the ones that did. I'll have my first hatch from a little hen brooding them in about 17 days so we'll see how much difference that makes.