Homebrew PCBs

Sharpest tracks for me were with lith film (Ilford)-- I use this for 
unsharp masks for BW negatives so I always have some on hand.  I do 
almost all my stuff now using Avery Clear Full Sheet Labels (when I 
am in a hurry) or Xerox mylar film.  With the avery labels I usually 
use 20 mils as the smallest trace width -- going to 10 mils I find is 
chancy.