Can you imagine a world where you effortlessly obtain process color consistency throughout a product line, regardless of the printing platform? This may sound like a pipe dream, but it is actually possible. The Flexo Quality Consortium (FQC) has been working on a project that will aid in making this color matching dream a reality. Using ISO Standard Datasets for Global Standard proofs, the same file can be effortlessly used across presses and processes. Testing has proven we can use standard proofs and curves to align files and expectations across the supply chain.
In short, the FQC team has collected data from numerous G7 aligned pressruns, executed all over the U.S. It then analyzed the data by press type, narrow web, wide web and corrugated to identify which Characterization Reference Print Condition (CRPC) best represents the color gamut for that segment of the industry. This CRPC can then be used as an industry wide aim to assure all printers and designers are on the same page.
The CRPCs are a set of seven reference print conditions to be used for communication of color expectations from design through printers. They were published by ANSI (American National Standards Institute) in 2013 as CGATS (Committee for Graphic Arts Technologies Standards) as the U.S. standard CGATS 21. In 2015, these datasets and methodology were approved by ISO as ISO 15339. Part 1 defines the process for usage, while Part 2 has the seven datasets. These datasets represent gamut sizes from coldest offset news through very wide gamut digital devices. They are all using G7 (ANSI CGATS TR015) methodology for common tonal appearance and common hue angles of the primary inks, per ISO 12647-6 Graphic Technology Flexographic Printing. Image 1 depicts the seven CRPCs.
This project has been completed in three phases. The first phase was the wide web segment, which was completed in 2007. This project identified CRPC 5 of CGATS 21-5 as the most accurate aim for wide web printers and designers. In 2009, the narrow web phase of the project was completed and identified CRPC 6 as the most accurate aim for narrow web. This project included surface and reverse print with UV and water based inks on film and paper products.
The FQC committee just completed the third phase of the project with postprint corrugated. This article will outline the project parameters, process and data analysis of the venture.
The third phase of the project was titled “Postprint Near Neutral Dataset Assessment and Gamut Alignment.” The mission statement was: Determine if postprint using near neutral calibration (NNC) can be used to recommend common aim characterization dataset for supply chain partners, i.e. brand owners, design, premedia and print.
In short, the committee assisted with printing multiple IT8 (TC2011) targets on at least 10 postprint pressruns with multiple substrates (coated and uncoated), using aligned hue angles for the inks per ISO 12647-6 (plus or minus 5 degrees). The data was mathematically aligned using NNC curves, if need be, and the resulting color gamut was analyzed and compared to CRPCs to identify the common aim point.
In order to print a desired common tonal appearance across various print methods, it is necessary to share common hue angles of the primary inks, per ISO 12647-6, and to communicate color expectations throughout the supply chain using an established CRPC for postprint corrugated.
One of the most critical components of this project was using inks that adhered to ISO 12647-6, plus or minus a hue angle of 5 degrees. This assured that all of the printers were essentially coloring with the same crayons.
There were a few datasets that did not adhere to the correct hue angles and they were digitally adjusted using Heidelberg Color Toolbox software. It is important to note that when the hue angles of the inks were aligned per ISO flexo standard, the color gamut increased by about 15 percent. This goes to show how important the proper hue angles are, and that not all process colors are equal.
The inks were not necessarily mono pigmented. For instance, you may have to introduce phthalo green to adjust the hue angle of cyan.
Once the correct inks were sourced the plates were made using the target seen in Image 2. It contains the IT8/7.4 2005 Random chart and standard process control elements.
Many printers around the U.S. participated in the project. Print samples were collected on coated and uncoated substrates. A total of 15 coated and 10 uncoated pressruns were printed and collected to assure a broad spectrum of data collection. A minimum of 12 printed sheets were collected for each pressrun, with one pulled every 10 sheets. The samples were then sent to Clemson University or Printron, who read in all of the print samples.
Image 3: Left, 14 dataset prints compared to CRPC datasets; right, 10 uncoated prints compared to CRPCs.