When creating that perfect printed piece, weeks or months of research, writing, revision, and design may pass before final files are ready to send to a printer. With as much effort that has been put into this project, you’re going to be searching for a commercial printer that can make your dream become a reality. There are two main printing methods today: offset and digital printing. We are here to define both forms of printing below and provide more context about how they are best utilized.
What Is Offset Printing?
Offset printing, sometimes referred to as offset lithography, is the standard process for producing high volume printing. While new methods exist, offset printing still remains king for commercial and specialty printing, such as packaging. Ideal uses for offset would include mass-produced direct mail pieces, catalogs, books, booklets, publications, newsletter, calendars, brochures, pocket folders, postcards, and much more.
The Offset Printing Process
A difference in offset printing when compared to digital printing is the use of plates in the printing process. The process begins with preflighting the files, which refers to the process of confirming digital files are correctly formatted to the desired specifications. It is during this prepress process that files are checked for adequate bleeds, image resolutions, etc.
After the proofing phase is completed, digital files are automatically separated by their colors and each color is laser exposed onto a coated aluminum plate. Plates for larger presses are typically forty inches wide. In the case of a process color (CMYK) job, four plates are required. Once plates are made, they are sent to the pressroom where they will be loaded onto plate cylinders on a press.
For ease of explanation in the simplest possible terms, the offset process relies on the principal that oil and water don’t mix. In this case, ink represents oil and fountain solution represents water with additives.
Ink, which is semi solid, is loaded into an ink fountain and then distributed in measured amounts through a series of rollers ending with the form rollers that apply ink to the plate. It should be noted that fountain settings, which can be adjusted in small increments across the width of the plate, are critical and set according to the ink coverage. More ink will be required for solid image areas on the plate and less ink where the images are lighter.
Fountain solution (water with additives) starts with its own fountain and is distributed to the plate through its own set of rollers.
After a plate has been loaded onto the plate cylinder, it revolves under the dampening rollers to be slightly moistened with dampening solution which keeps the bare aluminum (non-image area) from receiving ink. Rotation continues under the ink rollers which applies ink to the hardened image area of the plate but is repelled by the dampened aluminum. It should be noted that the application of fountain solution and ink happens almost simultaneously at up to four rotations per second, depending on how fast the pressman is running the press.
There are three cylinders in each printing unit: a plate cylinder, a blanket cylinder, and the impression cylinder. All three cylinders are steel. A super-smooth hard rubber blanket is attached to the blanket cylinder.
Once the plate receives ink as described above, the inked image is transferred to the blanket. Paper or other substrates are fed into the printing unit and ink from the blanket is transferred to the paper. The impression cylinder applies controlled pressure to the back of the paper as it receives ink from the blanket cylinder.
The paper then continues its journey through additional print units {on multi-color presses) and ultimately drops into the delivery unit of the press where it is jogged and stacked.
Benefits of Offset Printing
While digital printing may be offered as an alternative for smaller print runs, offset printing is the only way to go for higher volume jobs.
Offset printing also offers many inline coating options that can create different gloss or matte finishes on printed materials. For instance, UV coating will give your materials a high gloss finish while aqueous coating offers a lower gloss. Coatings can add a more elegant look and are great for making your finished product stand out. You also have the option to add coatings to certain areas of your product to make an important point or promo stand out from the rest of the page.
What Is Digital Printing?
Digital printing skips some of the steps related to offset and instead prints directly to desired materials. Digital printing occurs after electronic files that have been proofed are formatted into print-ready PDF files. Instead of relying on plates, digital jobs use powdered dry ink to produce accurate colors. It should be noted that digital presses are not the same as machines typically found in copy shops. True digital presses produce high quality that is comparable to offset.
The Digital Printing Process
The digital printing process often starts with the operator calibrating the press for any fine adjustments for print quality. The operator then reviews the digital artwork and make adjustments within the electronic design manager, rather than the press itself. The files are separated by colors within the files. The press uses powdered dry ink in the four CMYK colors.
At the center of each print unit is a finely polished coated metal drum. A laser writes the image for each color separation as a pattern of electrostatic charge onto the surface of the drum. These tiny points of electrostatic charge lift powdered dry ink from each color tray and hold it on the surface of the drum. As the paper passes around the drum, the powdered dry ink adheres to the paper with each of the colors being deposited in turn. The sheet then passes through a heated chamber which melts the powdered dry ink and fuses it onto the paper surface.
Benefits of Digital Printing
Digital printing is great for producing small batches of printed materials as it generally provides a quicker turnaround than offset printing with lower front-end costs.
Another popular use for the digital process is variable data printing (VDP). Every sheet through the press can be personalized in multiple fields by using data from a spread sheet. When used for direct mail, VDP dramatically increases response rates.
Printing with Premier Print Group
At Premier Print Group, we have almost 50 years of experience creating high-quality printed materials. By choosing to partner with our team, you can be assured of receiving superior quality and customer service. Contact us today to get started!
