gEDA-user: A great tip for DIY PCBs using inkjet printers and transparencies

[Paul Surgeon <surgpub@telkomsa.net>]

I was battling to make PCBs using the photo etching technique with an inkjet 
printer and transparencies until I ran across this little gem of info.
http://astro.umsystem.edu/atm/ARCHIVES/JAN02/msg00287.html

The common problem when trying to make positive plates with inkjet printers 
and transparencies is that the black is never dark enough to block all the UV 
(I've been trying for 2 days without success).
Also stacking the positive plates gives fuzzy edges because of the thickness 
of the transparencies.

The trick is to use GREEN as the mask and not black because most inkjet photo  
cartridges are dye-based and contain Photo Yellow which is a natural UV 
filter plus Photo Cyan which contains a UV inhibitor!
Pure green is half yellow and half cyan when printing in photo mode and it 
creates a good UV mask even though it is easier to see through than black.
Just make sure you have a decent photo cartridge and use photographic mode 
when printing so that the photo colors get used.

The author of the article above used a Canon inkjet printer but today I tried 
it out on my HP Deskjet 5550 with a HP 57 tri-color cartridge and I made 
perfect 5 mil tracks!

Just want to share this info because I know a lot of people throw the inkjet 
and transparency technique out of the window because they don't know this 
trick.

Regards
Paul Surgeon