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FLEXO Magazine : July 2008
..-\.r \".... e ' What is I!: TEST? TEST is a joint effort between the FFTA and complying educational institutions to expand technical skills required by a continually advancing flexographic process, bringing state- of-the-art professional development solutions to the flexographic industry. . TEST Technical Tidbit: Each month TEST will feature a technical tidbit from one of our part- ners.lfyou have a question you would like to be put to TEST send it to: email@example.com Our question goes to our friends at Dunwoody College of Technology I am looking for some sort of tolerance or target regarding wet ink trap for flexo printing. The FIRST 3rd edition skirts this issue and doesn't address this. Also, please explain 188.8.131.52 Print Contrast states that a starting point for establishing print contrast is: Cyan >= 20% Magenta >= 20% Yellow >= 20% Black >= 15% Unlike the SWOP or GRACoLspecifications, FIRST does not supply numbers for wet ink trap- ping. UV print technology flash cures the inks immediately, making the point moot. For non- UV uses, FIRST recommends a rub test (MEK Rub Resistance, FIRST3-184.108.40.206.8). Because flexo is such a heavy user of Spot colors, process wet ink trap numbers often don't pertain. Print contrast does speak to the issue of 4/C process as it focuses on the amount of shadow detail reproducible in a printed 4/C photographic image. The FIRST 3 numbers of 20C, 20M, 20Y and 15K are a typo. FIRST2 properly orders them with the yellow at 15 and the black at 20. Our feeling at Dunwoody is that these numbers are terribly conservative and unreflective of current best practices, or even mediocre press control. We normally achieve Print Contrast numbers on a narrow web, water-based press on coated pressure sensitive label stock in the mid 30's for black, cyan and magenta and the high 20's for Yellow. In regard to balance, it is fine for the black print contrast number to be higher than the cyan and magenta and the yellow to be lower which reflects the reality of differing ink densities. For the sake of gray balance in the 3/4 tone and shadow ends and coherent shadow detail, we find it advisable to keep the magenta and cyan print contrast numbers close with the yellow 5-7 points below. Print Contrast, to review, is a number reflecting the amount of density difference between a 100% swatch of a single ink and the 70% tint of the same ink, run through a simple formula programmed into a densitometer. The higher the number the better. The higher the number, the more apparent shadow detail in a printed image. The Dunwoody College of Technology Graphics and Print- ing Technologies program is a two-year course offering three program tracks-Design, Prepress, and Press. Regardless of the track that students choose, all classes incorporate state- of-the-art equipment in conjunction with hands-on learning. Dunwoody received the Harper Flexo College of the Year award in 2002,2003, and 2006. Dunwoody College of Technology, an FFTA Educational partner since 1999. II. .. TEST About our TEST Partner: .... Founding Sponsors Ron&Katherine Harper HARPE
Flexo Sustainable Fall 2008