Next stage was to etch the board (remove the unwanted copper). Ferric Chloride is probably the most widely used chemical for DIY purposes but it is dark brown and will stain ANYTHING it comes into contact with. I used a virtually clear etchant produced by the manufacturer of my boards. It took about 25 min to eat away all the unwanted areas with the chemical at 45 deg centigrade. It was then rinsed and the remaining film, which was protecting the tracks, was removed with some Acetone soaked Kitchen Roll. It's important not to touch the bare copper as the grease in your fingers will damage it, hold the board by the edges.