What is a black mask file and when do I need one?

A black mask file is an extra file that tells the printer exactly where to apply a special effect such as Raised Spot UV or Metallic Foil. Because these effects run as a separate pass, the mask, not your color artwork, guides where the finish lands. You need one whenever your order includes a spot finish or foil on select areas.

• Paint the effect areas in 100% black (K) and leave everything else white or transparent.
• Keep the mask shapes solid, with no gradients or tints, so the coverage is unambiguous.
• Build the mask in a vector program such as Adobe Illustrator for clean, precise edges.
• Supply it on its own layer or page, sized and positioned to line up with the print file so the effect registers with your design.
• Name the file clearly, for example front-foil or spot-uv, so it is not mistaken for a print layer.
• The black areas mark where the effect lands. The rest of the piece is untouched.
• Because these effects run on separate machines, a shift of up to 1/16 inch can occur, so keep fine detail away from tight registration.