Well, today i tried making my own pcbs - for the first time and I messed up 
I’m using copper clad boards sprayed with Positiv20. I know the artwork has to be mirrored, but does it also have to be a negative image (so the tracks are transparent) I cant work it out…i did it like this:
Printed out the the mirrored artwork so the tracks, drill holes etc are black (positive image correct?) on a transparacy, placed this on a lightbox with ink side up, and then placed the photoresist side of the board on top of that, then exposed as normal…
I then developed the boards and I could see the tracks turn dark in colour (this is the resist right?), they came out nice n sharp, I then washed with water and put the boards in the tray with fC - this is where it went wrong…and i got in panic…
The resist/black areas (tracks, drill holes etc) should turn to what? copper right? and the uncoated areas get dissolved, or does the resist stay on during etchin, then once all the uncoated copper gets dissolved you remove the board and scrubb the photoresist off with wirewool leaving the copper tracks behind…?
If anyone can give me some pointers using the positiv20 and how the artwork should be printed (positive/negative) it’d be appreciated… I’ve got a load of walkthroughs and pages bookmark, and also read the guide on the site but as u’ve read it aint it home for me 
Cheers
Dan