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.
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.
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.
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.
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.
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.
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.
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