An article we featured in July about an experiment to determine the best color order for process-color screen printing drew an insightful response from master printer Michel Caza. Learn what he sees as the key factors for getting the most accurate and intense colors out of a four-color inkset.
By Michel Caza
You have many options for calculating the amount of compensation required, including using design software (e.g., Photoshop) or manipulating the curves in the RIP software that drives the imagesetter or CTS system. Also available are programs specifically designed for profiling and color compensation, including GretagMacbeth ProfileMaker 5, GMG Color Server, and others.
Line count: How high can you go?
Few graphics printers realize the full potential of the screen-printing process because they limit themselves to line counts of 85 lines/in. or less. The first four-color-process image I ever printed was a 133-line/in. graphic, which I produced 44 years ago. I believe all shops should strive for a minimum resolution that is comparable to the line rulings common in offset lithography. It’s essential to reach this level of detail in order to stay competitive with offset and emerging digital technologies.
Experience has convinced me that, with tight process control, any shop can routinely produce halftones of 150 lines/ in. Believe me, if you work with highline-count images day after day, they become no more difficult than working with 75-line/in. halftones.
Putting the pieces together
In producing the prints depicted in Figures 1-3, our primary goal was to reduce variables by controlling all the parameters of the job as closely as possible. We began by correcting the curves for our images based on an ICC profile generated with GretagMacbeth ProfileMaker 5.0. From the corrected file, we produced film positives on an Agfa imagesetter, with halftones at 150 lines/ in. and using elliptical dots. The screen fabric used was calendered Sefar yellow mesh with 450 threads/in. and a thread diameter of 27 microns. The mesh was stretched to 23 N/cm and coated with a single coat of Sericol Dirasol 902 emulsion on the substrate side with a Grafica GF-3040 EC automatic coating machine. We exposed the screen in a Grafica GF- 3040 EXCB/A angular contact frame.
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