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FLEXO Magazine : July 2007
4 2 F L E X O J U LY 2 0 0 7 w w w . f l e x o g r a p h y . o r g tEsting & analyses 4.+#9;Drying speed of the ink. (For example, participants in this study noted that UV inks can be directly correlated to press by anilox volume. Again, drying speed of the ink is critical. UV inks wet out well with the doctor-bladed hand proofer and drying rate isn’t a factor with UV inks. Though other substrates can be a factor, this study tested on film substrates.) Now that a benchmark for the deposit rate of the doctor-blad- ed hand proofer roll is determined, the compensation needed in volume for the next set of anilox rolls can be made. The follow-up testing should demonstrate an exact correlation to the press. Final Correlation The initial testing focused on determining the deposit rate when comparing proofer to press. This approach offered the data needed to fine-tune the doctor-bladed hand proofer anilox rolls so that they would match press-transferred volumes exactly. This follow up demonstrates that volume compensations can be made in any volume range, allowing an exact color match when proofed in the lab. This allows an ink technician to have matched proofer rolls at his disposal for proofing different volume ranges and cre- ating accurate color matches. This is how to set the anilox standard- ization as well as set the standard- ization for the proofer rolls. This correlation process dem- onstrates that as ink film gets thinner, the proofer volumes require a higher percentage of additional volume. This is partly due to the drying speed of ink. Inks dry much faster at lower volumes. The results charted in Table 1 demonstrate that there is a curve in volume compensation: There is a 10-percent volume increase needed for 200-360 line screens, a 15-percent volume increase for 400-600 line screens, and a 30-percent volume increase for 660-1,000 line counts. Once these compensations were cal- culated from the results of the initial study, a new set of proofer rolls with the adjusted volumes were produced for correlated ink matches. Once the compensated anilox volumes were applied to the doctor-bladed hand proofer, the proofer density readings cor- related with the press readings. All density readings were +.02 - .06. This proves that the doctor-bladed hand proofer is capable of transferring the amount of ink needed to get a correct color match. Based on the results of this testing, it is clear that the doc- tor-bladed hand proofer (with specific pre-determined proofer roll volumes) is a very efficient tool for the ink lab: When an ink match is needed, simply find the proper line count and volume to match the approved colors. The doctor-bladed hand proofer also saves time when hosting customers for color approvals at press-side. Most importantly, on a day-to-day basis, the ink technician has the proper tool for matching color and making inks “press ready.” This minimizes make-ready times for ink-matching. Printers are encouraged to try this comparison themselves. They will get the same positive results. I have tested a variety of solvent ink systems and they all differ from each other. Do your homework when standardizing your color matching process and the results will be positive. Use the same solvent blend that is used on press when making ink for press. Simulate the press environment as much as possible.
Golden Anniversary Commemorative Journal