lithographic printing

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Lauren Rowles, GMN
By Lauren Rowles | Dec 20, 2018
GMN's holiday calendar 2019

As part of our yearly tradition, GMN has produced another custom calendar for the upcoming year. Apart from the functional value offered in helping to track the months and days of the year, these calendars also serve as a fun way to show off some of GMN’s decorative capabilities. In collaboration with our Seattle, WA Division, this year’s calendars were created at GMN’s Monroe, NC Division.

This year, we decided to make some exciting modifications to our calendar design, while still maintaining some of the same design elements as in previous years.

On the top strip of the calendar, there is an overlap spin pattern. This finish has been included on some calendars in years past, however, this year we enhanced the spin finish by taking the spin and dragging it along the metal surface, creating a dynamic look that reflects light in an interesting way. While this capability may seem common, the challenge that was posed by this application was achieving the drag spin at an angle and selectively. In order to contain the drag spin finish to only the top area, the process required laying down a resist layer over the desired area before the drag spin was applied. This resist layer protects the bright and other areas of the metal on which we didn’t want the spin to be applied. However, the resist ink can be difficult to work with at times, as it needs to be strong enough to withstand the drag spin, but gentle enough so that it can be removed after the spin is applied.

In addition, to complement and enrich the movement of the drag spin finish, a carbon fiber design was printed on the background of the calendar. Achieving the right balance of color was critical for printing this pattern because the color needed to have enough contrast to be visible but also be light enough to allow for the aluminum material to show through. Lithographic printing was used to print the months of the year onto the metal and create the halftone gradient pattern that is featured. Lastly, the GMN and logo and the year were embossed to add extra dimension and value to the calendar overall.

The entire GMN team is proud of the final product and is excited for it to take us into the new year!

Debbie-Anderson-GMN
By Debbie Anderson | Jul 27, 2018
Example of lithographic printing at GMN

Lithographic printing, an offset printing technique, is based on the basic principle that oil and water do not mix. It is a process in which ink is transferred from a photographic plate to a rubber blanket, which then presses the image onto the printing surface. Allowing for extremely tight tolerances and consistently high-quality images, GMN’s sheet-fed lithographic process is frequently utilized for printing graphic overlays and labels.

While lithographic printing is often performed on standard substrates such as paper and vinyl, GMN walks the unbeaten path by predominantly using materials including polycarbonate, polyester, and aluminum. Lithographic printing at GMN utilizes UV-cured inks. GMN also offers custom color matching services to help customers achieve their exact specifications and uphold brand consistency. To formulate a custom color, the different colored inks are meticulously weighed, poured over a flat glass surface in carefully measured proportions, and mixed together using a putty knife. With projects requiring custom color matches, a small sample sheet is first tested on a machine called the orange proofer. This counter-top machine is simply a condensed version of the actual printing press, that allows GMN to test the color and make necessary alterations before the final production run.

The first step in lithographic printing is creating the artwork on a photographic plate through a chemical process. Similar to the process of developing photographs, lithographic printing also requires the creation of a “negative” and a “positive” image. First, a thin aluminum plate is coated with a hydrophobic material so that it attracts oil (ink) and repels water. The plate is then selectively exposed to light, thereby curing the hydrophobic coating only in areas comprising the artwork. Finally, the coating from the remaining areas is chemically stripped off and the plate is ready for use.

The lithographic printing press consists of a series of rollers laid next to each other. The foremost roller transfers water, placed in a tray beneath it, to the photographic plate. The ink is manually applied to the second roller with a putty knife, which then wets out to the entire cylindrical surface as the roller spins and transfers the ink to the plate. The photographic plate, carrying the artwork, is wrapped around the next roller in the series. Given the immiscibility of ink and water, the ink adheres only to the artwork on the photographic plate, while the water adheres only to the remaining background.

On the other side of the photographic plate are two other rollers called the blanket roller and the impression roller respectively. The blanket roller simply acts as a medium to transfer the artwork from the plate to the substrate. When printing, a stack of printing sheets is placed on the top tray of the machine. A gripper grabs one sheet at a time and wraps it around the impression roller. The artwork on the photographic plate is imprinted on the rubber blanket roller, which in turn transfers it to the substrate on the impression roller. Then, the ink is cured by exposing the printed sheet to UV light. The process is repeated for every unique color in the image.

Ideal for high-volume manufacturing, a lithographic printer can run from 3,000 to 6,000 impressions per hour, with the largest sheet size being 18”x24”. It can produce detailed and intricate artworks with half-tones, gradients, or a four-color process (a four-color process uses a CMYK color module to create four separate dotted patterns, which when printed on top of each other, yield the required color). However, lithographic printing comes with its own limitations. It can only accommodate substrates with thickness ranging from 0.003” to 0.020”. The printing system is not compatible with metallic or conductive inks. Also, the ink used is very transparent, and typically requires extra layers of printing for opacity.

As multiple factors go into consideration before selecting a suitable printing technique, GMN works closely with each customer to understand the project needs and requirements to determine the best printing solution for every unique application. To learn more about our other printing technologies, visit our blog on GMN’s printing capabilities.