Thanks for your suggestion, that makes total sense. I'll give it a go next.
Regards
Matt
>>>>>>>>>>>>>>>>>>>>>>>
---In Homebrew_PCBs@yahoogroups.com, <boman33@...> wrote :
At the edge of your board outside the final area place a small piece of aluminum foil. That way you have a spot without any exposure at all. Similarly cut a small notch in your artwork or have one side smaller than the PCB. That way you get an area with 100% exposure without any loss through the artwork. Those two areas will work as a process reference and they have 100% contrast. If they are good, then the issues are with the artwork.
Bertho