Does anyone know what kind of ink studios use for 
cels on the hand-inked areas (or for the lines in 
hanken mono cels)?  

I've just finished my first fancel/copy (below) 
and learned by screwing up a lot.  The ink I used 
(Koh-i-noor acetate drawing ink) makes beautiful 
lines, but they are very fragile and easily 
scratched.  The hand-inked lines on cels from the 
studios are much more scratch resistant (don't 
ask what I did to find that out).  Any 
suggestions for alternative inks (other than 
marking pens)?  Thanks!