...but this is what works for me. This is my second consecutive 90% hatch after dismal failures in prior attempts, so this thread is my attempt to "pay it forward". These are three dozen Cuckoo Marans eggs from a local organic farm/vineyard/winery. Yes, I used a Sharpie. I weigh all eggs on Days 1, 10 and 18. The goal is to achieve a weight loss of ~12% on Day 18. It's my belief that there is no "magic number" for humidity (until Days 18+). Humidity is merely a tool used to manipulate weight loss and the ideal humidity for you will be something for you to figure out based on how much weight your eggs are losing, not based on what somebody on the interweb tells you. For me, in my 'bator, in my climate and at my altitude, I aim for the following: Days 1-17: 35-40%, drop to 25% for a few hours before adding water. Days 18+: 58% and I allow it to rise as it may when the peeps start hatching. This increased humidity on Days 18+ is essential in keeping the membraned slick and pliable, otherwise the peeps will be shrink-wrapped and they will die. Ventilation: as much as possible while still maintaining humidity. Day 18: Out of the turners and into the cartons. These silly little styrobators don't hold enough water for my climate, thus the extra dishes and sponges. In the holding cell... Marek's vaccine... In the brooder... A cute little feather-legged poulet... Final result: 27 of 30 hatched. There were 6 duds which I left in there because they were not stinky, but I ain't counting those against my hatch rate.