hard boiled eggs?

hi al you chicken keeping friends.

I have a quick question for you all.  Whilst eating a couple of hard boiled eggs for breakfast in a hotel recently I found that some shells come off very easily and have a membrane underneath that helps you to shell them and some come off in tiny pieces, even leaving large pits in the white of the egg?

Is there a reason for this?

Many thanks for those of you who can help as its not vital but made me wonder.


Thanks

Jools

As above, if you want to shell a lot of boiled eggs for pickling keep the eggs for 2 weeks before cooking and they peel cleanly.

And then 3 hens and then another 6................................................?