paint a white protective coating on back of glass tile?

Question

I draw some picture at the back of a glass tile and want to find some way to paint it white and protect it, but I find using roller do not look good, using spray can will mess up the edge of the glass tile, is there any better way to do this. I have a lot to do therefore I need a better solution. the tile is 4x4" x 1/4" high.
Thanks.

but I have to this thousand times, tape will take forever, I want to find more industrial solution to solve this problem.
I do think of idea like cd printing, use silk screen to do it, if someone has any suggestion are very welcome.

Answer 1

Spraying is still your best bet. Use some blue masking tape (painters' tape) on the edge. Rub the tape with your thumbnail to make sure to get a clean edge.