By Ron Ellis
Ask any printer who has forsaken the route of transforming their company in an “integrated communications solution provider” and instead has made the strategic decision to focus squarely on exceptional high-end color printing, and they’ll tell you color fidelity is as important as any other aspect of their operation. And despite all the technological advances over the last 10 to 20 years, inks remain the lifeblood of the making color stand out paper.
As a result, many printers have worked to calibrate their production processes to meet the standards set by GRACoL (General Requirements for Applications in Commercial Offset Lithography) or SWOP (Specifications for Web Offset Publications).
During the course of a calibration to GRACoL or SWOP, a critical part of the process involves an evaluation of the inks. During this evaluation, the ink solids and traps are compared to LAB color values specified in the ISO 2846-1 standard. This test is the first step in the calibration, and if the ink fails, the rest of the calibration is halted until the ink issues can be resolved.
Inks can be deceiving, because even though most inks are based on CMYK, they perform very differently. Part of this is based on color and pigments, but part is also based on other needs such as dry time, printing process, and other more mechanical needs.
Without a standard, all inks live in their own isolated world (Even with a standard such as ISO 2846-1, they seem to live in their own world). Most inks may be CMYK inks, but they all have different behaviors and tendencies, and most exhibit different visual behaviors. Most inks currently are not purchased because they meet a standard, and indeed most inks on the market were not designed to meet a specific standard. Standards are important. Once you have a standard to compare inks to, it becomes easier to evaluate one ink against another on a common playing field.
It during these comparisons that it becomes evident how much variation exists among printing inks. While ink is a large variable in printing, it would not be fair to say that ink is the largest variable in printing. The interaction of ink with paper, fountain solution, and other mechanical issues are also large variables, and the difference in dot gain between one paper and another can be substantial and there is no ‘easy’ way to qualify paper.
The ISO 2846-1:2006 standard is based on SWOP, and although this document was first released in 1997, it has been revised many times since to give us the current document. It is an important document because it provides us with several things we need to know about ink to print correctly. The first is that the ink is the correct color.
This means that when we lay down ink, we are actually getting a standard color from this ink. These values are measured using LAB measurements (which can be measured with a spectrophotometer or spectrodensitometer). The second important metric that this standard provides is the overprint values, again in LAB.
By checking these overprint values, we can be assured that the inks are trapping/overprinting correctly. These are both important characteristics of an ink. By starting off with an ink that meets the ISO 2846-1:2006 specifications, we can be more confident about being able to print to standards such as GRACoL or SWOP.
It seems like a simple question but when ask ink companies this question, the results can be unsettling. The response does not build confidence, but many ink companies are not used to being asked these questions. Often if you ask to be passed to the ink lab there is a staff member there who will know which of their inks are ISO 2846-1:2006 compliant. They may be able to discuss with you the results that have had with these inks.
Compliance means the ink has been tested in an independent laboratory and found to meet the specifications of ISO 2846-1:2006. Though developing an ink standard may seem basic, the history of printing involves the craft aspect of the industry, and nailing everything down to standards is a slow process.
Ink standards are important because they give us a starting point and a recommended ink set when we are trying to achieve good reproduction. Prior to standards, the choice of ink sets was often based on word of mouth, or an opinion from a trusted source.
While an opinion from a respected individual can be invaluable, color reproduction itself is often hard to quantify and describe, and for this reason ink standards are valuable. Knowing that an ink meets a specific standard allows us to know that we are not starting off on a wild goose chase. At this point there are enough ISO 2846-1:2006 compliant inks available from manufacturers that we can meet many of the other needs in addition to the colorimetric needs that have led us to ink standards in the first place.
Just because an ink is ISO 2846-1:2006 compliant doesn’t mean it will naturally work with a standard such as GRACoL 7 or SWOP 11, although it does demonstrate that the ink does contain properties that indicate it would have a good chance at being a successful ink when tested with these standards. Both GRACoL 7 and SWOP 11 reference ISO 2846-1:2006 specifications and the GRACoL 7 documentation supplies the LAB values used in ISO 2846-1:2006. So to be compliant with GRACoL 7 and SWOP the ink solids and overprints need to pass the ISO 2846-1:2006 specification. These tests are easy enough to perform with a good densitometer, spectrophotometer and an understanding of density and LAB values. The end results however are dependent upon more than ink, and relate to the paper, chemistry and other mechanical issues.
Standards are important because they help us create a predictable manufacturing process. They also help us perform quality control checks and make sure the product the ink vendor has provided us is consistent and isn’t changing. With standards we can perform checks on the product being delivered to us as well as the products we deliver.
As print buyers and customers demand more consistent results, these standards help them define which vendors can provide the services they are looking for. More importantly they also help us be able to provide these services for our customers. While some may look at standards as a drag, or an extra expense to be avoided, they can also be used as a tool to reach new customers and provide exceptional service.
About the author: Ron Ellis is a prepress consultant specializing in workflow training and integration. He worked in the commercial printing industry for 18 years and brings a strong background to all aspects of prepress. He has consulted on numerous CTP installations and he provides color management, integration, training, workflow development, and troubleshooting solutions to the graphic arts community. He can be contacted at 603-498-4553 or through his web site at www.ronellisconsulting.com.