infertile sign for egg hatching?

[onie13]

what is the bad sign of the egg for hatching or infertile? you have any picture for the infertile sign of eggs? i have the fertile picture for the 21 days chicken egg.. tnk for advance for help

 

[sonjab314]

Here is a helpful link https://www.backyardchickens.com/t/...g-candling-pics-progression-though-incubation