thanks so much for advice people gave me. turns out all 3 eggs were duds. btw today is day #23. after taking advice from you guys and a breeder on the phone, i candled all 3 eggs once more. again the air sac was still high, there was a darkish shape but not huge. i pipped a little hole in the shell at the air sac end, to see if there was any sign of movement/life inside. all 3 eggs just had...well, egg. the darkish shadow was the yolk. :| i'm really disappointed because it's been a long 23 days. however the breeder i spoke to had speculated that the darkish shape might have been a chick that died early, the the air sac still high, and so i feared that i might have killed the chicks with a poorly calibrated incubator. so i'm pretty happy that i didn't kill any chickies, and also i feel glad to know where i stand. i have 3 silkie eggs which the breeder (different breeder) assured me are fertilised, so after calibrating the incubator i'm going to leap right into my next 21 day agony of waiting.