Burnie69 is spot on.. Once day 18 comes I up the Humidity, if it ever dropped below 55-60 the chicks died in shell.
Day 18 "lockdown" is the main/harder bit of hatching for me, temperature aside.. I strictly sit on my hands and don't open the bator till hatch day as it will let humidity escape and I'll end up with chicks stuck or unable to pip/zip.
But I'm lucky I've just had two successful broody hatches in the hedge lol.
But will be doing ayam cemanis in next week or so, there too dear to wreck by bad incubating skills