Four of my quail eggs arrived with hairline cracks covering half their surface, and I was able to repair them using candle wax; all four hatched! I can't say how well this works for larger eggs, or for larger cracks, but I wanted to share for anyone facing similar issues. All I did was melt a drop of wax off a birthday candle and "coax" it across the shell surface using a lighter. The flame never gets hot enough, or is out long enough, to heat the egg contents. More than keeping bacteria out, I believe this allowed the eggs to keep moisture in. The four of them had larger air cells than the rest, but not dramatically so. Here's pics of one of the repaired eggs, and the chick that came out of it.