I have no educated idea really, but I'll throw an uneducated one out there... Ink the first pass in with black, as white reflects a good deal of the laser light on the second pass. I think Barry had a good idea with etching. Never tried to eat away an eggshell with vinegar, but it does make sense, as that's how coloring eggs for Easter works, I'm assuming.
I think they'll slice your brain up for examination upon your demise, Tweakie. It sure works in mysterious ways.