Printwear

February '13

For the Business of Apparel Decorating

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Getting the Press In Spec N What's this color management? Color management is a methodology used to translate tone and color from the original image to fit the tone and color capabilities of a specific garment and a consistent system of screens, inks and press. Color management systems for four-color process printing essentially focus on a proofing device that is calibrated to output a series of neutral grays with C+M+Y from highlights to shadows. Next, the press is characterized and calibrated to produce the same neutrals throughout the tonal range. Then, once on press, the operator simply ensures neutrality and nearly all the colors which are within the printable gamut will translate faithfully from original to reproduction. Simulated process requires far more experimentation per image because simulated process is not color manageable in its current state. There is no such thing as a ready-for-use sim-process ink set which is calibrated to the separation software. And, it is likely the sim-process proof that accompanies the files or films has little affiliation with the tone and color of the reproduction. Read between the lines There is a silly and singular barometer for quality process color—the line count. If you're new to the game, I suggest starting with a 45 lines-per-inch count (LPI). When everyone and everything in your system supports 45 LPI five times in a row, bump the line count to 55 LPI. Increase from there as systems prove you can and if it is good for the bank account. As you do so, keep comparative logs that track setup time, time-to-color and cycle rate, stoppage (times and durations) and scrap rate. This log will serve to show the sales team comparative quality and price. Is it really proof? The name "proof " implies some level of evidence that a given set of files or films have qualified to translate the original image into a quality reproduction from your system. For the proof to have any value to the press operator at all, the proofed image should be surrounded by color bars, tone scales and gray scales. Also be 100 percent certain that these images (the color bars, etc.) were separated along with the live image, as opposed to cut and pasted from a different set of screens onto the new mesh. A printable image is one that we can trust to be measurably consistent. We can trust images once they are verified on the proof and the color bars on the files or films are consistent with the proof images. If they are, the files and films are worthy of the screen room. (Note here: if the screen department tries to tape off or block out the color bars, and tone and gray scales, stop them—they are the roadmap to effective and efficient color.) Better or worse: the screen department Beginning with the screen department, the best advice for production is "process control must precede color control." All separations and color management systems assume the process is consistent. There is no way to "fix" files or a set of films with coatings or exposures. Instead, ow that we understand how repeatability and consistency in production leads to proper color management and quality prints, let's look at how to make sure the press is consistent. The platen surfaces must be flat and the press must be calibrated to be parallel. All of the carriages (in the print position) must be on the same plane, parallel and equidistant to all the blades and meshes, which must be parallel and equidistant from all the platens. The off-contact gap should be at a minimum to convert static tension into suitable printing tension and to allow the image to "pre-form" on the underside of the mesh. The maximum gap should be less than would cause dimensional error and below the elastic limit of the mesh. (Tip: If you get to press at 25 N/cm2, use 3/16" as a reference point.) Set the flood-bar at about 0.0015" gap so the printing blade can't run short of ink. Run the flood at 80 percent of maximum speed to reduce the lag of first and last flooded ink. The edge of the printing blade should be no more than 50°. For the highest density, a beveled edge is best. To print the most consistent dots on all parts of the screen, use a bi-axial or hinged blade that runs at 80 percent of maximum stroke speed. Set this blade between 0º and 5º with minimum pressure to compress the garment and clear the mesh—seek balance between the pressure and the printing tension. Balance would result in zero blade-buckling and zero platen-deflection irrespective of the press. pw 2013 February Printwear PW_FEB13b.indd 59 | 59 1/21/13 11:22 AM

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