Spot colours - or 'specials' as they're often called in the industry - are one of the last dark arts left in printing. The process of creating and managing spot colours for vector and raster images is shrouded in mystery, thanks to their inability to be cheaply hard-proofed, but with a bit of confidence - and Adobe Acrobat Professional - the process is actually very straightforward.
Spot inks can either knock out the background (which punches a hole through the CMYK inks ensuring the spot colour is crisp and vivid) or overprint the background (meaning that they sit on top of the CMYK inks and the colours blend). Previewing the different effects of knocking out and overprinting inks was virtually impossible until Adobe revamped how spot inks and additional channels were handled in Photoshop, InDesign and Acrobat.
