Another post just reminded me that I had said I would post the results of my little air cell experiment on this last hatch, so here it is. My hypothesis: If I could see where the air cell was, I would be able to predict where the duckling would pip. What I did: At each candling, I drew a penciled circle around the edge of the air cell, which resulted in a growing set of concentric circles. At lockdown, I placed the eggs in an egg carton so that the air cells were facing the viewing window, and waited & recorded. Results: I was surprised at just how thoroughly uniform the results were. Every single one of 9 eggs that hatched pipped in the same location relative to the air cell. When looking at the eggs, the pip was located at the far left edge of the air cell, approximately halfway between top and bottom. Surprise: I also noticed that zipping took place roughly along the outer edge of the air cell, moving right, and tended to stop at the far right edge--at which point the baby began to push. Notes: I would love to see this experiment repeated in other incubators, and with other breeds and species. I also intend to continue to experiment in the same fashion, and from now on intend to make a point to place eggs so that the far left portion of the air cell is visible from the window--I had a couple eggs this time that had most of the air cell visible, but not the far left where the pip would be expected, and it was very frustrating not knowing if they had pipped. Unfortunately, both ended up being eggs that never pipped at all, but I would have liked to have been monitoring them the whole time.