Homebrew PCBs

Haveing just taken a shot at John for being condecending to a new 
idea, I should admit that I also think his Scratch and Etch idea is 
totally brilliant.

Has anyone ever just gone and tried this? I have done it with a 
simple plotter, a scribe in place of a pen, and a sheet of glass 
painted black. It works like a dream. My goal was to make a digital 
sun dial, not to etch PCBs, but I can't see why it wouldn't produce 
finer results than any other method.

The only trick is finding a paint that drys quickly to a hard (not 
brittle or tacky) finish so that it is completely and cleanly 
removed by the scribe. Also, the plotter may need to be a nice big 
one like my tough old HP (God rest its soul) because the scribe is 
going to drag more than a pen... probably.