Homebrew PCBs

Mine(900) has a painted white square at the front, and next to it a
notch cut out, I dont know if its looking for a reflection from white
and then no reflection from the notch, or if its no reflection on
black, reflection on white, then a sensor under the notch.

I have tried on pcb (shaped like a cd...) but its not good, very
uneven and lots of beading, but I have not got new ink yet, still
waiting for the cis system