The egg shell is actually a porous membrane, eggs sweat to soften this membrane, this make it easier for the embryo to brake free.

Diet or retention may affect this membrane, I am trying to understand how.
Meanwhile when my eggs start sweating I add water and keep hydration 100%, this seems to help them hatch.

A few times iv seen babies slit the membrane but die without hatching, this is not normal, I am trying to understand why and how we can avoid this.