I've read that if the membrane is white they will have trouble. It was pipped for, probably, 18 hours. Once I could really feel the membrane it was incrediably tough. I've read this can happen with shipped eggs, which this was. I could see that the chick wasn't making progress and was not willing to watch it die (as I did last month with a pipped egg). I pulled on the membrane after softening it -still quite thick- and the chick made it out shortly after, seems fine. I'm glad I helped, big chick!