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What is Spot Color?
In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run.
The process of offset printing in full color consist of Cyan, Magenta, Yellow and Black (CMYK). When the need to match a particular color (a background or specific color in a logo or company color) on a printed piece, the use of a spot color is utilized. The main reason that the spot color is utilized is to maintain the color fidelity or accuracy of the color throughout the print run.
Normally any or mostly any color can be created from the CMYK color model, but when large areas are being printed with the specific need of a special color, the control envelope on the printing process is limited, and sometimes a compromise on color is required. An example is an image that has a blue sky (Cyan and a hint of Magenta), and green grass (Cyan and Yellow) has the requirement of any of the base colors being used (Cyan, Magenta and Yellow in this case) for the special color - say Purple (almost equal amounts of Cyan and Magenta) , then the amount of the contributing color to the special color will be limited to either be the correct amount for the green grass, the blue sky or the Purple special color, all three demanding different degrees of Cyan.
The printer needs to have a special file created for the spot color in addition to the CMYK colors. This spot color will eventually be a plate that utilizes an extra printing unit on the press to print the color to the printed sheet.
There are several systems developed and in place for matching specific spot colors in the industry. In North America, the most common has been designed by Pantone Inc. The matching system developed by Pantone is called "Pantone Matching System" (PMS) and this system has approximately 1,000 different pre-defined colors that can be mixed from an array of base inks that are called "Pantone Colors" - these Pantone colors are the base inks that are sold by the company. A printer normally refers to the PMS number of the ink in the specification. Once the specification is established, the client and the printer refer to the color by its PMS number.
To print in the spot color, the printer will take the specified PMS number, refer to it in a Color Chart which identifies the Pantone Colors (Base colors) that will be required to mix the PMS numbered ink, and further the percentages to be mixed to achieve the desired color. Computerised scales are available to printers with high volumes or the requirement to be accurate. The color achieved by the compterised scales are achieved faster and with less waste. This offers efficiency to the printer who can thus offer cheap printing of business cards, flyers, post cards, brochures, catalogues, and books.
The PMS color mixed to achieve a color on coated paper will print with a different hue and density on offset stock, non white or off white stocks. This is the reason that the company that establishes these matching standards offer color swatch books in both offset and coated stocks. Printoutlet utilizes a computerized system to achieve the exact color that is required, thus reducing errors.
It is possible to mix two or more spot colors to create further colors with interesting effects. This practice is employed in the 2 color duotones (an image printed in 2 colors only) or tritones (an image printed in 3 colors only) - Although it is possible to use this process for 4 colors (quadtones), it is not used as often as the variety of interesting effects it offers as the special washes and mixing charges that go with the use of spot colors is prohibitive.
The use of the base Pantone colors is also possible in the printing process, and are employed extensively, such as Reflex Blue (a Dark Blue Color) - a Base Pantone Color that is used very often as a special spot color in a printed piece.
The proofing of spot colors is not conquered in the Digital process of todays printing technology, but since a spot color is defined as a specific number in a matching system, its reproduction is almost always assumed to follow a PMS Guide or color chart. Some analogue processes have offered a proofing process by means of an image on a laminated layer on clear acetate, but the yellowness of the acetate, especially when several layers are utilized, renders this process a guess at best for the representation on the proof.
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