Egg shell mosaic

Occasionally my son forgets that I am keeping all the shells to craft with and simply cracks them.  I have been experimenting with egg shell mosaic and this is my first attempt. I used drawing inks but i don't think that the colours are strong enough.  I plan to try again but will use my alcohol inks next time.  I would love to have some white egg shells to play with but I get so few of them and they are just too beautiful to crack and look stunning sitting unadorned in a red glass bowl.