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.Basically, an ink colour is ready-mixed to produce a particular colour, as in Pantone® 032 below.
So if you were producing a 2 colour card with, for instance, Black as the main colour for text then a 2nd Pantone® colour would be chosen from a colour swatch.
To produce this job would entail making 2 sheets of film which would then be used to make 2 printing plates for the press.
The more spot colours used, the more film and plates are needed, hence the increased costs.
To keep costs down it's possible to create tints of a spot colour without needing extra film or plates. The example (shown below) consists of Pantone® 032 at: 100% + 50% + 25%.
These 3 'shades' would all be on 1 piece of film & 1 plate.
100 % 50% 25%
WHAT IS A SPOT COLOUR?As with the paint example above, a spot colour is basically a pre-defined colour that can be reproduced at any time. There are many different colour references but the industry-standard formulas are provided by Pantone®.
WHY BOTHER WITH SPOT COLOURS IF I CAN ACHIEVE THE SAME RESULT WITH CMYK?