The screen printing process brings many traps to people. Spelling, alignment, balance, word usage and pattern deformation are all factors that hinder the separation of color work. However, in the absence of standards, we may be unlikely to change the status quo that does not work. The production of the printing machine due to the failure of the color separation is a very high price. The most advantageous way is to reduce the failure rate, thereby increasing the effective printing production. Here we solve the five common problems in printing color separation, which is the increase in success rate and production efficiency.
Examine the top five color separation errors
The type of digital file used during color separation affects the type of error you will encounter. Design patterns composed of several colors may require a considerable separation process. Since most color separation problems are also related to background printing, these errors mostly occur in the case of dark clothing printing. In the case of light-colored garment printing, more basic errors often occur, and these errors are easier to predict. Your company may have different color separation errors than those listed in this article, but identifying and dealing with the problems mentioned below will undoubtedly increase the effective printing machine production time.
Fifth largest color separation error: a color is missing
The color separation work was completed, but when the clothing was printed, it was found that there was an image that had not been copied, and it was not visible on the positive picture, screen, and final print (Figure 1). Such problems are commonplace in vector graphics created by corelDRAW or Adobe Illustrator, and color separation is often done by editing the original file. If the original has many color blocks that must be converted to different colors to generate all positive film, then missing a color block or an error when selecting colors will become a problem.
Figure 1 The fifth largest color separation error: a color is missing
Solution: Use macros to help complete the color conversion and replacement in vector graphics. The macro quickly selects each image part of the same color. Some software such as Illustrator allows to select similar color parts in the pattern, which simplifies the color separation work. corelDRAW has a macro to find / replace colors, which can help to select all the color blocks; in addition, it also has a print preview function, which can check each positive image file in detail before outputting the film. Compare the design manuscript with the positive image file to find out any problems.
Fourth largest color separation error: insufficient background color on dark shirts
This problem is particularly tricky because it requires some foresight to discover it. The technique to solve this problem is to understand the ink used and to know how much background color is really needed to complete a bright print on a dark shirt, and the color tone of the shirt will not affect the overprint color or value. A common cause of insufficient background color on dark shirts is related to the method of creating the background color.
One way to create a background color for dark clothing is to turn the background around the original design pattern into black, and then create a duplicate image in Adobe Photoshop. Then convert the copied image to L * a * b color mode. The lightness (1ightness) channel is used to create the background color, as follows: copy the lightness channel, paste it into the original file, and then execute the reverse command. The resulting channel serves as a base background color. The problem at this time is that the highly saturated colors, such as the red or magenta of the fire truck, often get a medium gray / dark gray after coming out of the lightness channel. Using this method can only give the above colors 40% -50 % Background color (Figure 2). If the separation file is printed with such a light background, the final print will appear dull, lifeless, and may even change the color completely.
Figure 2 The fourth largest color separation error: the background color on the dark shirt is not enough
Solution: Gradually understand the ink used and what materials the ink must be printed on to produce bright, vivid colors. There is no shortcut to solve this problem. If it is required to print 100% white as the base color to create a bright red, then this part of the image must be enhanced in the base color. One of the best solutions is to use the color range tool in Photoshop to select the most saturated red in the image (or any color that needs to adjust the background color), and select a low blur in this tool to avoid adjusting the background color too much In the gradient color, only the brightest part of the image is adjusted. Once the selection is completed, turn to the background color channel, and then only increase the density of this image part in the background color through the curve menu to compensate for the color saturation. An additional advantage of this method is that it can find all areas in the image that contain such highly saturated colors, so that no omissions will occur. [next]
The third largest color separation error: poor color mixing in the gradient area
This error is usually caused by hasty. It may also be attributed to the use of the stylized solution in Photoshop. When Photoshop separates colors based on the original, the colors appear blocky rather than smoothly mixed. If it is the latter reason, the color taken out of the gradient color appears uneven in the final color separation file, and a lot of details are lost. The image composition includes a gradual color that is divided into 4 or 5 flat paint colors instead of smooth transition colors. Some designers call this effect multi-tone separation (posterization).
Solution: Depending on the source image, there are several ways to create a smooth blended shape in Photoshop. One of the best methods is to use a dual system.This method may sound complicated, but in fact it is surprisingly simple, and it can save a lot of time compared to the method of creating complex selections through paths or hand-drawing in shapes. This dual system uses a combination tool to avoid some selection restrictions in Photoshop.
First find a mixed color that must be separated. Then use the color range tool in the original file to select the most saturated part of this part of the color. Next, create a new channel through this selection. The resulting new channel may look dull and unusable, so use the curve tool on the selection to make it consistent in all highlight areas (you can also use the level tool). Then use the resulting mask as a selection by holding down the Ctrl key and clicking the mask in the channel menu. So you can use this selection as a complicated path to separate the subtle color selection from the color part that you want to process through the curve tool or the "Image> Mode> Duo" command. The key is to use a constituency to create a deterministic area, resulting in a better constituency. Using this method to create color separation files simplifies the entire process of having to create a detailed path in Photoshop.
The second largest color separation error: trapping problems or leaks on dark shirts
This is one of the most troublesome problems in the color separation process of screen printing. Dark clothing printing almost always uses trapping, and the surface color completely covers the background color. The background color of white must be thin, and the surface color must slightly overlap with it to prevent white from being revealed. Leakage does indeed make the pattern appear thin and poorly printed. When there is a problem of white leakage, the production department usually does not think that the responsibility is on its own. On the contrary, it can only mean that the design department has not considered that the white will expand slightly, and the surface color needs some space to solve the above background color expansion and overprint deviation. And other issues. When the printing machine vibrates or the frame is loose, light-colored clothing that does not need to be white can also cause trapping problems. As each color is printed on the garment, you will see the printed pattern deformed.
Solution: Perform an image test to understand how much trapping is required for different conditions and different clothing colors. This method will solve the problem of trapping. Once there is a problem, it should be carefully recorded so that the next time the similar job is processed, the design department will have a standard that can be based on so that the correct trapping process can be performed on the image. But the most maddening thing is that some images do not need to be trapped on some clothing such as hemp gray shirts, but they need to be trapped when printed on other colors of clothing. The problem of insufficient trapping volume will be more obvious on white shirts. Under these circumstances, establishing trapping standards will not only help solve the immediate problem, but also prepare for any problems that arise at some point in the future.
At present, there is no simple way to selectively create trapped areas in vector graphics. Background trapping usually involves creating an additional file and then adding a white outline to it based on the amount of trapping. Software such as corelDRAW and Illustrator have trapping features, but they cannot selectively create the necessary trapping areas. In screen printing, the ability to selectively create trapped areas is indeed needed to prevent some internal areas of the color from clumping together and to ensure that the external areas still cover the background color.
Trap in Photoshop is even simpler. Just copy the background channel, and then use the curve or magic wand tool to modify the channel, and only select the outer area (this is especially effective for some images with regular edges). Next, quickly shrink the selection, and then narrow the selection by trimming or removing the outer area.
The first major color separation error: there is no digital proofing of the finished document
This is the number one mistake in color separation. Digital proofing is the basis we use to discover all other errors. Taking the time to reconstruct a file with split channels in Photoshop will make other color separation errors in the top five more obvious. If you know how to reconstruct the color separation channel with ink color settings in Photoshop, your success rate will rise significantly.
Solution: Select the shirt color you plan to use, create an alpha channel, use this color as a barrier layer, and then create other color separation channels according to the desired printing order. If you have completed the above steps, but find that there are still some other problems, then you should slow down and understand what the problematic area looks like in the digital proofing. The potential problems in printing will already show up in digital proofing.
Although the problems you see in digital proofing may not be exactly the same as the problems that will occur when printing, you can almost always find a valuable clue. For example, the background color reveals a tiny line or the overprint color looks dull. These are all trapping or density issues. Gradient colors may be poorly mixed, or the colors may look uneven. According to experience, the final document will hardly be much more detailed than the digital proofing. If digital proofing looks pretty good in Photoshop, you really have a good start-it is possible that the printing will avoid handling the top five color separation errors mentioned above.
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