Colour Theory - Spot Colour

SPOT COLOUR

In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run.

The widely spread offset-printing process is composed of four spot colors: Cyan, Magenta, Yellow, and Key (black) commonly referred to as CMYK. More advanced processes involve the use of six spot colors (hexachromatic process), which add Orange and Green to the process (termed CMYKOG). The two additional spot colors are added to compensate for the ineffective reproduction of faint tints using CMYK colors only. However, offset technicians around the world use the term spot color to mean any color generated by a non-standard offset ink; such as metallic, fluorescent, spot varnish, or custom hand-mixed inks.

When making a multi-color print with a spot color process, every spot color needs its own lithographic film. All the areas of the same spot color are printed using the same film, hence, using the same lithographic plate. The dot gain, hence the screen angle and line frequency, of a spot color vary according to its intended purpose. Spot lamination and UV coatings are sometimes referred to as 'spot colors', as they share the characteristics of requiring a separate lithographic film and print run.

Computer methods

There are various methods to incorporate rather sophisticated patterns of spot colors in the final prepress artwork. Software applications such as Adobe InDesign, Adobe Illustrator, CorelDRAW, QuarkXPress and Scribus may generate spot colors as additional channels. Adobe Photoshop can also be used to generate soft edges (widely known as feathered edges) of spot colors. The dissolve effect provided by Adobe Photoshop layer patterns can be generated for any spot color.

Optimizing usage

Generally the cost and potential for problems for a print job increase as one adds more spot colors, due to the increased cost and complexity of added process inks and films, and requiring more runs per finished print. However, because of the complicated process, spot colours are effective at preventing forgeries of money, passports, bonds and other important documents. Money printing for example, uses secret formulae of spot colors, some of which can be seen by the naked eye and some that can only be seen by using special lights or applying certain chemicals.

4C vs. Spot

Spot colors are premixed inks that the printer lays down (Pantone is most commonly used) vs inks that are mixed on the fly during press operation.  Due to this Spot colors have less color variance.  Spot color also have a larger gamut then CMYK and can achieve some colors not possible with CMYK like vibrant oranges.  If budget allows consider setting your print job up as 5 or 6 color, CMYK for general color in photographs and one or two Spot colors for a nice color that will be used throughout the piece or in a very important spot.  When impressive metallic colors are needed, spot metallics are the only way to go.

it is important to use “swatches” when designing if exact color matching is important. Swatches provide a designer and client with a printed example of what a color will look like on paper. A selected swatch color can then be chosen in Photoshop (or a similar program) to insure the desired results. Even though the on-screen color won’t exactly match the swatch, you know what your final color will look like. You can also get a “proof” from a printer, which is an example of your printed piece provided before the entire job is run.