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Bangladesh Textile Today - A Comprehensive Publication for the Textile & Apparel Industry
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Advantages & disadvantages of CMYK screen printing

Print is the major concern for a merchandiser. A merchandiser having sound knowledge in print technique always gets advantage. He can easily find the way of solution if any difficulties arise regarding print issue. Possibly, even likely no one would stand before a merchandiser to say that this print is not workable for some particular fabric or the color is not achievable because of print technique, if he really understands deeply in print. For any print problem this is merchandiser who has to come forward to endeavour solution. Innovative idea & problem solving method would help in this. So knowledge in print technique, knowing advantages & disadvantages of print methods is really important. This article discusses on print technique CMYK in practical point of view.   *This is just sharing of authors ideas based on the experience on job. And this is not important that everyone will be accepting all of the views & way of working. What is CMYK   CMYK is the abbreviation for Cyan-Magenta-Yellow-Black .This is also called process print. A process print is reducing color to minimize cost. Suppose a print has seven color so this seven can be minimized into four that means Cyan-Magenta-Yellow-Black .Using this four color we can get the same color effect / tone as the seven color way. Design experts decide what color can be merged with other color to minimize the screen & then they create design file Photoshop. This is really an amazing idea in print technique. As the CMYK print is reducing color so this has some practical difficulties when it is being applied.    The "K" in CMYK also stands for key because in four-color printing, cyan, magenta, and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. Some sources suggest that the "K" in CMYK comes from the last letter in "black" and was chosen because B already means blue Halftoning. In printing, a key plate is the plate which prints the detail in an image. When printing color images by combining multiple colors of inks, the colored inks usually do not contain much image detail. The key plate, which is usually impressed using black ink, provides the lines and/or contrast of the image. However, in two-color images where neither color was black, the key plate might have been printed in the darker of the two colors. But To save money on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta and yellow.   The CMYK model works by partially or entirely masking colors on a lighter, usually white, background.   Difference between CMYK & RGB print:   RGB – (Red, green, and blue) is color created by mixing together light of two or more different colors.  Here white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. RGB can only be viewed with natural or produced light, such as in the computer monitor, and not on a printed page where as CMYK is stand for printing process. During design file graphic designers convert the file into CMYK because in designing stage designer works in RGB form for creating design.     Halftoning   To understand CMYK one must know Halftoning. This is the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size, in shape or in spacing, thus generating a gradient like effect. Tiny dots of each primary color are printed in a pattern small enough that human beings perceive a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter as and less saturated than the color of pure magenta ink.   Cyan and yellow produce green; cyan and magenta produce a purplish blue, yellow and magenta produce red & all three of them resulting in black.     This close-up of printed halftone rasters show that magenta on top of yellow appears as orange/red, and cyan on top of yellow appears as green.   CMYK in the screen print   CMYK is once used only for paper printing but later the technique is extended to all kinds of print because of its low cost & easy process. As the garment is the major ground for displaying print so naturally this technique is being used now on dress in a large scale.      Step no 1 is showing, on a black color ground a white layer of print is given to make the ground visible. Because as mentioned earlier CMYK is possible to do white / lighter ground only.   Step 2 a yellow color ink is put as a part of  Y – Yellow process . Step 3 after putting yellow ink how the ground is looking. Step 4 a Cyan (Blue) color ink is put as a part of  C – Cyan process . Step 5 after putting Cyan ink how the ground is looking. Step 6 a Magenta (Pink) color ink is put as a part of  M – Magenta process . Step 7 after putting Magenta ink how the ground is looking Step 8 a Black color ink is put as a part of  B – Black process . Black is to give details on print line that gets more visibility. Step 9 after putting Magenta ink how the ground is looking & this is the final output of all CMYK process.   Advantages of CMYK technique: 1) Less color process / screen for print. 2) More productivity. 3) Cost minimizing. 4) Good hand feel because of using less color on ground. 5) CMYK color can be used for different item of print because of common color way.   Disadvantages of CMYK technique: Using CMYK technique for screen on garment has lots of difficulties & disadvantages. If one is not experienced yet with CMYK on garment this article will help to work over it & those are experienced already they can put up new ideas that readers may get better solution.  However discussions here are based on practical experience.   1) Shade Variation: The most challenging for CMYK on screen print is ‘shade variation’. This is very common for CMYK technique - making print color /shade variation although in case of same ink, same operator & in the same day production. The shade variation may be one or two even some time ten shades can be appeared. Definitely no customer will accept this variation for his order which he is going to sell in store & the store will be full of different shade in one style. This will make his customer (end user) confused which color he can purchase. So, most of the time buyer will be reluctant to accept the variation. This is very important issue for screen print to inform buyer what is practical & which is not avoidable. In the CMYK technique shade variation is totally unavoidable but what we can do? We can minimize the variation & make buyer feel little less scared.       Extent of variation:   Above two pictures show black & white body print & the variation. In the first & second images three different colors in particular area are seen. If one body having excessive presence of red ink on the other body will have excessive of green color & in some other body yellow is dominating on the print. This is totally unacceptable & not to ship.     Why variation happens:   Print experts explained this as below:   a) The main reason of variation is screen. In the screen print factory use different type of mash/net. Some are in big dot/ hole & some are small. In big dot color passes more when ink is applied on garment & print looks bulky & not clean .On the other hand small dotted screen can produce smoother & fine print because through the small dot color/ink passes less . However for a detail print where a big no of image if require to display suppose a scene of village or city, factory usually use fine mash/ small doted net. Fine mash cannot pass color much than that of big mash. So this is very common that after one or two stroke of print on garment the hole of the mash get blocked by ink & the blocked. Factory washes the screen/mash in every 5-6 stroke to clean the blocked area. After that the blocking issue is totally uncertain & not possible to control fully.     b) The second reason can be identified as operator’s hand pressure on screen. In the CMYK, Yellow & Magenta produce Red but still red has lots of tone - lighter, darker, yellowish etc. It depends on the percentage of mixing color of Yellow & Magenta in liquid form. When operator put ink on the garment some time he press more on the screen with his rubber handle & color pass more . Or if he presses less on the screen color pass less. So in practical an operator cannot keep same pressure as previous stroke on the screen & garment gets variation in different tone of print.     c) Most of the cases factory produce garment print in different temperature or timing . Suppose in day time ,if the sky is clean & very sunny day, print color on garment gets dry quickly in compare to if the sky is cloudy or in moisturized weather or in night time . When the dry process gets little longer the tone might be little changed.   d) If the color mixing is not done properly the variation may happen during production & same liquidity of ink is necessary for all four colors. Mixing of old color in the new ink may be responsible for the variation.        e) Some time factory tries to use bad quality ink or mix good or bad quality to minimize cost. This is not wise to use bad ink for CMYK. It was seen bad quality ink is mostly responsible for the print variation.   Possible solutions:   a) Washing the screen properly in every 3-4 stroke of print on the garment. This will slow down the production but is good solution.   b) To put same pressure on the print screen this is good to use automatic machine. This will help to pass same portions of ink for each garment .Off course using automatic machine for the CMYK is really costly & in some way complicated also. However this may be a possible solution.   c) Different operator has different energy level so if you use different operators to print done on garment this may cause color variation. So try to use fewer operators & obviously use most efficient one.   d) Keep close eye on production what output is coming from bulk. Try to compare today’s production with yesterday or evening production with the morning one so that you can find the key point of color variation.   e) Proper mixing of color ink is important.   f) Dry the print in same temperature.   g) At the end if variation could not be avoided please inform buyer immediately with giving the reason behind the variation of print so that they can find a solution how to accept it. Usually customer ask to pack separately at least not to display same print in different tone in same shop.   h) Inform your customer beforehand during the order confirmation that what problem may happen in CMYK. This will help you & your customer not to be surprised at eleventh hour.   

 

August 2014
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