Homebrew PCBs

I've been following this thread with interest. Seems that direct 
printing of a PCB mask is something of the holy grail to us homebrew 
types.

One thought just occurred to me. Since they sell pens that you can use 
to draw your own layouts (i.e. Sharpie pens), how about finding out 
what ink is used in those and fill an ink cartridge with that?

I know this is obvious, but I've heard lots of other complex formula 
that don't seem to work and lead to clogging. The Sharpie ink seems 
based on a volatile solvent that dries very fast. The solvent may also 
help to resolve head clogging problems as it might be a self-cleaning 
solution. One problem I can see is that it may be so fluid that it 
would just drain out of the cart. But perhaps this could be resolved 
by altering the vent ports to allow less air in.

Hope somebody figures this out.
-Ted