By: Elizabeth Gooding, President at Inkjet Insight and Co-Author of “The Designer’s Guide to Inkjet”
Different companies have different needs and expectations when evaluating paper for use in their inkjet environment. At a minimum, a paper has to be compatible with the device, but the quality expectations will vary along with the relative importance of specific quality measures. It’s important to measure and also to prioritize the measurements that matter to you and your customers. Is it more important to deliver on gamut, show-through, small text clarity, edge clarity or to avoid mottle and coalescence? Or are they all important? The answers to these questions on print quality priorities generally vary by market segment. For example:
- Transactional print mostly focuses on show through and small text clarity, but when corporate color matching is required, gamut comes into play.
- Gamut, mottle, coalescence, and text clarity are always important measures for direct mail quality.
- Many commercial segments have a higher standard for all areas of print quality than transaction and most direct mail.
- Those working in packaging and labels may be looking at media types beyond paper and need strong performance in text clarity, gamut (hitting those brand colors) and edge clarity.
Earlier this year, Inkjet Insight surveyed inkjet users on their evaluation priorities. Regardless of application focus, all respondents said that small text clarity and color gamut were important or very important. Optical density and show-through were also important, or very important, to 93 percent of respondents. You can view the executive summary of the research here.
What does it mean to measure print quality?
First off, there is the matter of compatibility. Gianluigi Rankin, director of global product management at Memjet, recently wrote about how media choices for inkjet are expanding through the evolution of ink, primers and coatings and the media itself. More options mean more testing, possibly with and without precoating or primer. There are too many options and interconnected cost/quality variables to select paper without measured testing.
While inkjet does not have a defined quality standard for testing, experience has shown that there is a minimum achievable range of performance needed on the papers used in each market. So where do you start?
Inkjet manufacturers typically provide lists of “qualified” papers that have been deemed compatible with a particular device. To qualify for this list, a paper must successfully print a standardized test pattern with a defined ink volume at rated production speed. A test typically runs for at least 2000 lineal feet and must be dry at the end of the run with no visual wrinkles. This test process is about ink, machine, and paper compatibility. The key here is not to mess up the inside of the press with roller contamination and web breaks from wet output. This first step is pretty basic.
Once the printed output has passed this first step, it is checked for color to color bleed, coalescence, and mottle. If the output is visually unappealing, the paper is normally rejected unless color saturation, mottle and coalescence can be minimized by adjusting settings.
This may be all that is done for a paper to be “qualified.” This tells you that the paper will run, but not the quality you can expect. Often an OEM is also performing a measured print quality analysis on listed papers, but this information is not normally shared with the OEM’s customers. Customers are clamoring for more media and the fastest way to expand the approved media list is to run it through the minimum of testing for compatibility and then let the customer decide if it meets their standards.
USE MEASURABLE IMAGES FOR PRINT QUALITY TESTING
Qualified does not mean quality!
Without measurement data, it’s hard to know if your print expectations, better or worse, align with those of the person qualifying the paper. The OEM may be supporting customers in many market segments; what is acceptable to one may not be acceptable to another. This subjective approach can lead to surprises and disappointment if a “qualified paper” does not meet the customer’s print quality expectations. It can also lead to papers being eliminated from the qualified list that might be fine for mono applications or transaction printing or workbooks and less quality sensitive publications.
Without an agreed upon standard for inkjet quality, it’s hard for OEMs to qualify papers in an objectively meaningful way. Many categorize paper as 1-4 or with a star ranking. These categories or rankings bundle all of the aspects of print quality into a single, averaged measure. But as noted earlier, everyone has different priorities on the measures that matter.
That’s a problem if two papers with the same ranking produce very different results. One might have scored high on text clarity and low on gamut – or vice versa. A paper that was not suitable for full color inkjet might be great for mono applications like books or forms. Even with the top “score” how do you know if this paper is right for your environment? You don’t. This can be very frustrating to inkjet users with limited time and budget to qualify papers. According to research cited earlier from Inkjet Insight, only 28 percent of survey respondents were satisfied with the paper qualification data supplied by their OEM.
You are the decider on what quality means
Without an industry standard for print quality, and an absence of quality data from OEMs and mills, you need to determine which quality measures are most important to you and your customers and conduct the necessary testing. Keep in mind that these priorities may vary by customer or type of work. Here are the key items to test and measure:
- Optical density
- Chroma – CMYKRGB
- Show through
- Color gamut
- Color to color bleed
- Small text clarity
- Edge clarity
At Inkjet Insight, we call these Key Performance Indicators (KPIs) for print quality. We have evaluated and profiled 100’s of papers and other substrates for customers serving different application segments. This creates a valuable reference point for testing to enable evaluation within a target range on ISO measurements.
If you expect beautiful precision from your inkjet press, you need to be precise in your paper evaluation process. Machine, ink, primer and precoat all perform differently based on the media to which they are applied. Let the data guide you to quality.
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About the Author: Elizabeth has a rare ability to see design related issues from many perspectives. She has managed creative teams on complex design projects, selected outsourcers for major brands and helped print organizations to retool operations, focus their market positioning and educate sales teams to accelerate growth. At Inkjet Insight.com, Elizabeth works with a team of top analysts to translate those experiences into tools, data and content to help print organizations evaluate the potential of inkjet, optimize their operations, work effectively with designers and grow pages profitably. She is also founding member of the Inkjet Summit advisory board and a curious consultant constantly seeking innovative ways to help designers and printers hone their craft and drive new pages onto inkjet presses.