Printing in Color

by Jesse Smith

This is an introductory overview to the process of printing a color image.

The Pantone Matching System

The Pantone Matching System was developed by the Pantone Ink company, which prints convenient swatch books with numbers to identify various shades of colors, and the amounts of certain other inks that a printer would mix to achieve that color. The Pantone Matching System or PMS has become the industry standard for numerically referencing spot colors (a single solid or screened color). Many leading graphic design software programs also offer Pantone swatches to facilitate communication between designers and printers.

The Four Color Process

In printing, most full-color (e.g. photographic) image rendering is achieved by carefully blending fine dot screens of four prime colors: Cyan, Magenta, Yellow and blacK. (By contrast, computer screens display color in degrees of Red, Green and Blue; and therefore most digital camera images are RGB files by default.) Therefore, the printing of full-color images is usually referred to as a four-color process. The methodology of the process itself is discussed below.

Shorthand

Printers often refer to the items they produce in terms like 4/4 or 4/1. This is not a time signature; it indicates how many colors print on each side. 1/0 prints a single spot color on one side; the other side is blank. 4/0 prints a four-color process on one side; the other side is blank. 4/4 prints a four-color process on both sides; and 4/1 through 4/3 indicate a four color process on one side, with 1-3 spot colors on the reverse.

There are several methods of printing; and each one has its benefits and drawbacks.

Offset Printing

There are several types of what might be considered offset printing: they include everything from sheetfed lithography to rotary offset webfed. The essential concept of offset printing is that a plate is used to transfer ink from a pan to a rubber cylinder or drum, and from the drum to the printed matter; thus the image has been off set.

On jobs that only print in one or two colors, or for some jobs that use a lot of one specific color in addition to a process image, offset printing employs spot plates, which print a solid color in a particular spot. Additionally, offset printing can produce high-resolution prints in CMYK, using a plate for each of the prime colors of Cyan, Magenta, Yellow and blacK.

From a buyer's perspective, the biggest limitation to offset printing is the plate cost. For this reason, offset printing is typically more suited to longer runs; although recent advances in CTP (computer-to-plate) technology have helped to decrease plate costs for single-color jobs and shorter runs. (Previously, a printer would have to output films would would then be employed to make a printing plate; but new computer-to-plate machines essentially employs an advanced type of film as the plate itself, allowing printers to charge less for setup on most items.) One advantage is, most printers will keep plates on file for several years, thereby eliminating setup costs on exact repeat orders. Another advantage, and the reason that offset printing remains a mainstay of the printing industry, is that the offset process renders very high-quality images. Offset lithography is often recommended for art prints and other situations where very precise details are critical.

Digital Printing

Digital printing is great for shorter runs, of between just a few and up to perhaps a few thousand pieces, depending on the item and the press. The benefits are: no plates are required; variable data is possible; and a job may be run with little or no makeready (waste involved in setting up a job). The drawbacks are: the presses and the inks are very expensive; and the cost per item does not decrease substantially at higher quantities.

All color digital printing employs a four-color process, mixing Cyan, Magenta, Yellow and blacK (CMYK) to produce the color spectrum. As technology advances, this can be achieved through a variety of mechanisms.

Color laser printers use heat from a laser to fuse the different colors of toner (very fine particles of pigmented plastic or wax) to the printed stock.

Desktop inkjet printers use a print head with a very small nozzle to apply a thin film of very precisely mixed liquid ink. Some large-format commercial digital presses employ the same principle but on a larger scale. Other large-format presses use completely different types of nozzles. One type of nozzle, for example, will extrude a very fine mist of liquid ink particles which are then attracted to the printed matter in a specific pattern by a carefully controlled ion field.

Many types of digital printers, such as your desktop laserjet, only print in black. Thermal transfer printers use heat to transfer ink from a ribbon, while certain thermal printers (used in some fax machines, credit card machines and many corporate shipping departments) use heat to make a chemical change in specially treated paper.

Flexographic Printing

Web-fed flexography is most commonly used to print labels and other packaging materials. On a flexographic press, an anilox roller transfers ink to a flexible rubberized plate, which is wrapped around a cylinder; the plate prints directly to the web (a continuous roll-feed of printable materials, aka substrates) which is then typically either die-cut or sheeted. Flexo printing is well-suited for long runs and is often most economical at large quantities. Common packaging materials printed on flexographic presses include boxes, labels, and wrappers. Some flexographers print with solvent inks on plastic wrap materials, while others print with water-based inks on paper and synthetic substrates.

And many more

There are many additional methods of printing which this article does not discuss in detail. There are special presses used for foil stamping, and other special presses that use male-female clamshell plates for embossing. Screen printing in its various forms can extrude inks of extreme durability onto objects and printed materials, including CD's, T-shirts, outdoor decals, and mementos. Gravure presses maintain print consistency in process colors over very long runs of several million impressions by engraving the printable image directly onto a metal cylinder; gravure presses usually print with solvent inks, and are often used for major magazine publications as well as many types of wrappers and packaging. Also, when reading about the print industry, one often comes across the term "letterpress," which used to mean a printing press, often cranked by hand, that pressed letters of movable type directly onto a sheet of paper. Such methodology has become largely obsolete in the commercial world and in many print shops old letterpresses have been converted to fill various post-production finishing tasks such as scoring and sheeting. However there has been a major resurgence in the popularity of letterpress printing as an art form and many people around the world are enthusiastically procuring old letterpresses and settting them up in their basements to publish books and zines.

Conclusion

The reader, like the author, may often find themselves wondering, "which of these printing methods will cost less?" The answer clearly depends on the job and on the press. The one answer that's certain, is that everything always costs more than you think it's going to.

We hope you have enjoyed this introduction to the print industry. Please contact us if you have any questions or comments. Basementia also offers printing services for a number of common promotional items. Don't be afraid to ask for a quote if we haven't listed what you're looking for.

Good luck, and happy printing.