marking eggs

has anyone come across a good way of marking eggs i tryed uesin markers and sharpys but im scared im scared of messing up the egg and offen it harly leaves a mark theres menny eggs goin black in my incubator to im thinkin ive rolled them after candling and there bunk now.. but i donno cuz ive already had hatchlings.... think its just luck ?

I use a fine tipped sharpie or permanent marker and have never had a problem. The ink does not bleed or cause the egg any harm.