Simulated Color Separation in Screen Printing: A Step-by-Step Guide

The simulated color separation process allows obtaining better visuals on supports of all kinds of complex images and even photography. This is a process that has evolved a lot since the 1990s. At first, it was complicated to get good, long-term results on t-shirts and the ink could not print on dark surfaces. More tones, interaction with the background, and much more precise colors than with a simple color process are now possible to be made with a standard screen printing process. Well mastered, the simulated process gives tools to reproduce any image on any color background… This technique is an art and those who have the talent and patience to develop it see a vast range of opportunities open before them.

But what is the color separation process?

It’s a process of breaking down the colors into more basic ones. In very simple words – red and white give a pink color, and red and yellow give an orange color. All colors are just mixtures of several other ones. Seems simple, but what if we print on a transparent or black surface? Then in 99% of cases, an underbase of high-opacity ink (usually white) is printed on the garment and flash-cured before the other colors are printed, unless we want to achieve a so-called “vintage effect” often referred to as “soft-hand”. It comes in handy when a pale, grainy color texture is what we really expect. But then, what if there is a gradient or shading on pictures that we want to print? What if there are tiny holes on the surface we print on, as every piece of cloth? Those are the questions to be responded to by color separators. Their responsibility is to split the colors of a graphic just the way that it results in the best quality printing for the money that the client offers, propose a technique of printing suiting their needs and requirements. Color separation service is sometimes provided by the printer her/himself. However bigger printing companies often hire an expert at the craft to improve the quality of production.

Colour separation in photoshop is probably the most popular way of splitting colors nowadays. Photoshop is one of the most complex tools where one can work on the image, so most color separation takes place using these Adobe products. The separated design must be exported to the RIP raster image processor, where the gradients are given screen ruling, raster angle, and raster dot shape. Each color prepared in this way is printed separately on a transparent foil and then a screen is exposed to it, previously coated with a photosensitive emulsion. Thereafter, the exposed screen is rinsed with water. Where the emulsion does not collect light, because of a black covering area on the foil, it is rinsed out by opening the mesh screen through which the ink then passes.

There are different types of color separations

The CMYK process was a concept designed for printing machines such as we all have in our homes and offices, just larger in terms of volume of prints one can do sufficiently. This process involves the use of only four colors: Cyan, Magenta, Yellow, and blacK, hence the abbreviation CMYK. It’s the way one can produce almost any color on fabric whether it’s printed through a screen or by a digital printer. But it turns out that “almost” is not enough… Colors separated in a CMYK process often appear pale and limit a printer to only white or at least bright-color fabrics.

However, there is one more alternative. Spot color printing itself, usually recognized as a one-color technique, solved two problems known to CMYK printers pretty well. Instead of separating the colors and applying them layer by layer on a garment, one can just blend different colors or use PMS colors before application. With this, index color separation is used to get rid of halftones and replace them with purposely random dots (bitmap) therefore dismantling raster angles. This color separation technique erases unwanted shades and blurs on the edges. That makes for a clean and sharp print. This is why this particular technique is the most popular for recreating simple vector images, text geometric shapes, and very small details.

The simulated color separation process also uses spot colors. What distinguishes them is the additional possibility to use more than four colors and to apply halftones. It is very helpful for example when the print is meant to be applied on a dark garment, or if the print is very detailed, or when the colors on the original graphic are difficult to transfer with the simple CMYK palette. All this makes for vivid, opaque colors and faithful reproduction of the initial image. However, it demands specific professional knowledge to achieve the desired results. Choose the type of color separation that matches your needs.

A typical color separation process involves setting the raster angles depending on what kind of color is used. With a simulated process, all angles are set the same way. There is another disadvantage associated with incorrect sets of angle values, as the colors will look dimmer due to overlapping. That’s why for fabric printing services it is crucial to have professional color separation.

Raster frequency might be another trap for an inexperienced color separator. Technically, the higher the frequency, described in lines per inch (lpi), is, the more detailed the print should be. But also, higher raster frequencies raise the probability of a print error, considering limited mesh thickness with screen prints, and printing machine’s quality. Possible errors are, for example, disappearance or inaccuracy of high-resolution halftones, the appearance of smudges, uneven coverage, or hardness to distinguish the difference between colors of overlapping dark segments on the picture due to excessive amount of ink used by a printer.

Lastly,

It’s worth mentioning that digital or automatic color separation is not the same as the simulated color separation process. Digital color separation refers to all separation processes made using computer tools. Some color separators tend to call this process manual if they are using bare Photoshop facilities and selecting areas by hand. Automatic color separation is yet another thing. It’s a process that relays the selection and extracting of color layers to the software’s algorithm.

Fabric printing services, such as ours, offer all kinds of color separation for individual and business clients. Screen printing is also the only technique providing satisfying effects with complex images on a garment or uneven fabric.

 

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