A Holistic Approach to White Ink Laydown

The tools that we use to measure the uniformity, the mottle or graininess, are the BetaFlex Pro or the QEA PIAS-II meter. You can compute the Cyrel EASY BRITE Index using either of these devices and their measurements.

‏DuPont Desai Taylor Rickard Staggs Figure 3
Figure 3: Cross-section schematic showing how mottle and graininess is related to ink film thickness and poor white appearance

Figure 3 shows a cross-sectional schematic of the prints in Figure 1 and Figure 2 to better explain the visual quality differences. The EASY BRITE Index can be used as a holistic measure of white ink quality, rather than just looking at a uni-dimensional measure, such as opacity alone.

The index is a dimensionless measure that takes opacity and divides it by the measure of uniformity—either mottle or graininess. The higher the mottle or graininess measurements, the less uniform is the sample, and the worse is the quality of the white. The higher the opacity, the better the quality of the white. A simple mathematical calculation, using the following equation, results in an index that becomes directional: the higher the index, the better the quality of the white. (Note, the index is relative to the instrument used to measure uniformity and comparisons should only be made with the same instrument and its measurements.)

EASY BRITE Index = Opacity/(Measure of Uniformity)

We used a QEA PIAS-II meter to measure graininess and a Techkon SpecroDens to measure the opacity of the prints in Figure 1 and Figure 2. They both have opacities of 52 percent. But the graininess measurements are 0.9 and 5.9 respectively. The index values according to the formula are thus 52/0.9 = 58 for Figure 1, and 52/5.9 = 8.8 for Figure 2, clearly denoting the better result in Figure 1. This is not possible with opacity alone.

DuPont Desai Taylor Rickard Staggs Figure 4
Figure 4: Unmagnified view of laminated print sample evaluated for the EASY BRITE Index

A second example is shown in Figure 4. The EASY BRITE Index was calculated for both the screened portion and the unscreened portion. Figure 5 and Figure 7 show the corresponding QEA PIAS-II measurement result screens; graininess is read on the black channel as indicated by the red box. Since the sample was laminated, bubbles can be seen in the magnification, but that is part of the lamination process and they are present on both the screened and unscreened portions.

DuPont Desai Taylor Rickard Staggs Figure 5
Figure 5: QEA meter measurement of graininess – unscreened area

The opacity of the unscreened portion was 48 percent. The graininess measured 2.7. The EASY BRITE Index is 48/2.7 = 18. The opacity of the screened portion was 51 percent. The graininess measured 1.5 units. Following the formula gives us an index of 51/1.5 or 34. The EASY BRITE Index of the portion screened with the EASY BRITE screens is higher, indicating a better quality.

DuPont Desai Taylor Rickard Staggs Figure 6
Figure 6: 50x magnification of the unscreened area showing the imperfections in the ink laydown

Figure 6 and Figure 8 are the magnified photographs of the same area that was used to measure the graininess. You can see that the ink laydown on the sample that was printed using the EASY BRITE screens is much smoother, showing the validity of the directionality component of the index—higher is better.

Screens Cut Costs

Not only does using the right type of screen improve the overall uniformity of the print as quantified by the index, application allows you to use a thinner film of ink. This is analogous to using a very thick nap roller while painting a room. You need to use multiple passes to get the right ink laydown.

DuPont Desai Taylor Rickard Staggs Figure 7
Figure 7: QEA meter measurement of graininess—screened with EASY BRITE Screens

An alternate would be to use a roller with a better surface pattern to deliver less paint in one pass, but have it better distributed on the wall. You would be able to finish your room using less paint and in a faster time.

DuPont Desai Taylor Rickard Staggs Figure 8
Figure 8: 50x magnification of the screened area showing improvement in the ink laydown

This is exactly what the right type of screening will do for your print. Not only will you see cost savings by using less ink, but you can run your press faster and see improvements in overall quality of your print job.

About the Authors

headshot Shyamal Desai
Shyamal Desai is the DuPont Image Solutions technical marketing manager for the Americas. He has been with the DuPont Cyrel business for 17 years, and has had various roles in supply chain, product management and marketing. He has a bachelor’s degree in chemical engineering from Texas A&M University and a master’s in business administration from Rutgers Business School.
headshot Brad Taylor
Brad Taylor is a technical laureate for DuPont Imaging Solutions in Wilmington, DE. He has worked for DuPont for more than 30 years in various assignments in electronic imaging and imaging technology. He got his start in flexography as the technical team leader for the Cyrel digital photopolymer plate development in 1995 and has continued to focus on new digital photopolymer product development and project management. Brad has a Ph.D. in electrical and computer engineering from Carnegie Mellon University. Brad is a recipient of the 2020 Pedersen Award which recognizes and promotes technical and scientific excellence across DuPont
headshot Scott Rickard
Scott Rickard is a staff associate investigator at DuPont Image Solutions, working in the Tech Apps R&D team testing and developing new plate formulations and technologies in the flexographic industry. After studying and earning his B.S. in graphic communications and M.S. in packaging science from Clemson University, Scott started at DuPont as a technical service specialist in 2015 before transitioning to his current role in 2018.
headshot Douglas Staggs
Douglas Staggs is the technical sales account manager for the US West Coast and also segment leader for wide web applications at DuPont Cyrel Solutions. He has worked in the packaging industry for 35+ years in various management, technical and leadership roles specializing in prepress color management, pressroom improvement, efficiencies and production. Prior to DuPont, he worked as VP of business development and marketing at Trisoft Graphics and as packaging specialist at Pitman (AGFA).