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FLEXO Magazine : July 2008
TECHNOLOGIES & TECHNIQUES However, enter mottling. (Again mottling is the white speckles you see in the solid print areas.) It varies from roll of paper to roll of paper depending upon the smoothness of the paper and the formation of the fibers. We have associated it to the Sheffield numbers, the NUl (non-uniformity index) and other paper speci- fications that measure formation and smoothness. As those num- bers increase so does mottling. The ink is not covering all of the paper fibers due to lack of smoothness or bad formation of fibers, so white speckles show in the solid areas. There is a natural phenomenon that occurs with press opera- tors. When they see something wrong with print quality, they want to fix it. That's a good thing. Something you like to see with all your operators. Nevertheless there are times when you don't want them to do that. When our press operators see mottling they want to eliminate it. They have found in years past that all you have to do is give it more impression, it goes away. That pushes the plate into the paper covering those white voids and filling them in with ink. Mottling is gone. But as a result of the extra impression the high- light dots layover and we have harsh breaks and increased dot gain in all tonal ranges. It creates funny looking halftones with shadows and hard lines where you do not want them. Overimpression, as mentioned above, increases dot gain. That added dot gain causes shifts in tones for all colors. Therefore, with colors it would give the photo people a false color gamut. That would make the photo toners chase the press with toning, think- ing they added too much magenta or too much cyan and so on. The press operators ask, "Would you rather we have mottling?" No, but I explain it is not their job to fix mottling; it is the job of the paper makers. If I show the paper makers a newspaper with well printed solids and blacks, but harsh breaks, they are not go- ing to buy into the fact that they are at fault. Printing the best photo halftone quality is the job of the press operators. Making the best paper for newspaper is the mills' job. NO MORE COVER-UPS As I have said to our operators, over and over, covering up mot- tling by over impression is like turning up the volume on your car radio when you hear a squeak in your engine. The squeak seems to go away. In reality, the problem is still there; you have only masked it and it is causing other problems. Look at the photos of the various impression settings and see how the highlight dot shape changes with impression. It goes from round to egg shaped. Now, when I see harsh breaks, I look at the highlight dots. If they are lying over, most likely the im- pression is at fault. If they are still round dots it is most likely the way it was toned by the photo toner. Lesson learned: For the best print quality, understand the cause, work with your vendors as a partner, fix what you can and get them to fix what they can. . ABOUT THE AUTHOR: Frank Anthony is vice president of op- erations at the Chattanooga Times Free Press, Chattanooga, TN. He is a past member of FT A's Board of Directors and its Foundation's Board of Trustees, as well as a past chairman of the Board. Anthony has also served as a past president and secretary/treasurer for the Newspaper and Publication Flexo Users Group (NPFUG). Currently he acts as council leader for FTA's Newspaper Leadership Council. GRAPHIC COMMUNICATION INSTITUTE AT CAL POLY SAN LUIS OBISPO, CALIFORNIA GRCI WORKSHOPS Hands-on Graphic Arts Training for the Prinj Flexo FI RST 4.0 Walking the Process August 14 - 15, 2008 Do you need to produce high-quality repeatable flexographic printing? Experience the launch of FIRST 4.0 at the FTA/GrCI Flexo FIRST 4.0 workshop. FIRST (Flexographic Image Reproduction Specifications & Tolerances), is the newly-updated comprehensive set of procedures and specifications developed by the Flexographic Technical Association. Over a two-day period, participants will learn from the best in the industry* how to implement FIRST 4.0 in design, proofing, workflow, process ink QC, digital platemaking, flexographic printing, and process control using Cal Poly's "learn by doing" model of education. Flexographers who use FIRST 4.0 meet customer expectations by producing predictable, repeatable, high-quality results pressrun to pressrun. $499 Program Fee for 2-day workshop includes FI RST 4.0, dinner and lunches Register Online go to: www.grci.calpoly.edujworkshopsj flexoFIRST.html and follow links to secure page Contact GrCI For More Information call B05.756.2645 or firstname.lastname@example.org Come walk the process at Flexo FI RST 4-0! *Flexo FI RST 4.0 presenters include Malcolm Keif, Brian Lawler, Richard Black, Bill Whitfield, Mark Mazur, Jean Jackson, Carl Cecil, and Joe Tuccitto.
Flexo Sustainable Fall 2008