This article presents an overview of a technique that involves the use of an inkjet printer to generate a series of continuous-tone progressive separations that will serve as visual guides on press.
By Joe Raymond
The second color in the print sequence is the channel with the next highest percent coverage that is not black. This might be yellow, cyan, or magenta. The third color in the print sequence is the cyan, magenta, or yellow channel not yet printed. Black is the fourth, the last color printed.
For the color key, monochrome prints of all four printing films are made individually and layered to produce the progressive image. Operators often stack these films together in the order intended to screen print. As the print progresses on the screen press, the colored overlays are laid onto the screen-printed imaged to determine if they are on the right color path and to forecast what adjustments might be needed to keep them on track for the next successive prints (Figure 2).
The printer should adjust the strength or density of the solid patches of CMYK on press so that they’re visually close to those of the pleasing progressive. Then the printer should modify the press adjustments to produce the best tonality in the pleasing progressive (ignore the colors, control the tone). If these two steps are accomplished at press, the resulting screen print will be remarkably close to the CMYK color target printed on the inkjet before making the pleasing progressive.
How it’s done
Make the pleasing progressive print for the first pass. If you selected magenta as the first color printed, then it’ll be the only monochrome print you’ll need to produce. Go back to the Channels menu and select the other three channels (C, Y, and K). While they are selected, open the Edit menu. Select the Fill menu and fill the selected channels with white at 100%. The only color information left will be in the magenta channel. Your image will now print from your inkjet with magenta ink in the pixels from the magenta channel only.
The second pass progressive is made the same way. Open your original image and highlight the two channels that will not be printed in the second pass. One will be black, and the other will be either yellow or cyan. While they are highlighted, open the Edit menu, select Fill, and fill the selected channels with 100% white. Now print the result. You will have magenta and your second pass process ink printed combining two of the four total channels.
Now produce the third pass progressive by selecting black only and filling that channel with white. The printed result is the third progressive resulting from the combination of CMY inks without K printing.
The CMYK image was printed initially, so you already have the fourth (black) pass. You will probably find that your density for black will need to be lower than that of the inkjet print. This is because the inks printed on the screen press will be less transparent, making the print darker than the progressive with each successive pass. If the cyan, magenta, and yellow are balanced, the neutrals will be darker requiring less black in the black ink.
Now you can give your press operator a pleasing progressive print based on the image set for reproduction, a pre-determined print order based on coverage, and a gray-balanced printing sequence to follow visually at press. The printer only needs to make ink and press adjustments to come as close as possible to the tonal ranges and values found in the progressives. Go to press with the pleasing progressive and a set
of screen films for the same image. Print the image while paying attention to the starting density of the inks. Get as close as possible to those of the inkjet solids, and control the tonality and the neutral grays closely.
The next step
This article discussed how to build the foundation for the pleasing progressive. It’s up to you to refine this technique to create a high level of color accuracy between the inkjet prints you produce and the results you achieve on the screen presses you use in production. In time, you’ll find that mastery of the pleasing progressive allows you to easily and inexpensively get more from your screen-printing operation.
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Joe Raymond’s experience in the screen-printing industry spans more than 25 years. He has worked in printing, sales, technical support, and management.
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