And now it has worked again! From the eggs I put in the water, I kept 3 under the hen and 2 have hatched. The final egg I gave up on and decided to let the hen move on to caring for babies and to be free from sitting. (3.5 weeks)
That egg I brought in and candled. There is an air space, looks to me like 18 days. So I felt silly but I put it in a bowl of water. Water was moving so I walked away for a few seconds and came back when it was still. There, see, it is dead. Completely still, floating egg..... then very noticable jerk. then another. Then I dried it off and ran to the basement. My husband asked what I was doing with the heat mat, light bulb, bin and lamp. I said "it is alive! I am going to incubate it!" He said uhhh.... why not just use the incubator?
Right! So there it is in the incubator with the other eggs but I put it in a little dish to keep it separate.
I am sure that a live chick could not move in the water for whatever reason, so there is no guarantee that one that you think is dead, is dead, but certainly, without a doubt when you see movement and jerks, you can atleast be certain that one is alive when it is alive.