Coudray discusses the influences that ink values, software, and other variables have on the creation of effective simulated-process separations.
As with the first type, there are compromises. In the second case, the compromise comes in the form of increased press control. Dot gain is just as much a factor as with any halftone-based printing method. Additionally, color choice for the selected inks is very important. This is one of the main reasons why simulated process almost always relies on the use of some color-mixing system, typically Pantone, to designate the ink colors as accurately as possible.
Why your choice of ink is so important
Ink selection has much more of a bearing on your success than you might imagine. With the exception of dot gain it’s the most influential factor in final color reproduction. You’ll have an easier time diagnosing separation problems when you understand how the ink works in conjunction with the separation. The root issue is whether the inks you use are capable of delivering the color reproduction based on how you created the separations.
The goal of any separation is to reproduce the broadest range of tone and color with the fewest ink colors/printheads as possible. Traditional four-color process is the lowest common denominator for reasonable to excellent full-color reproduction. It works because ink transparency is fundamental to four-color-process printing. This transparency allows for excellent physical and optical mixing of the halftone dots. The problem is controlling the thickness of the ink layer. Variation in thickness changes the color, which means print pressures and platen height are absolutely critical in order to maintain consistency.
Other printing processes, such as inkjet, toner, traditional offset, and flexography, involve very thin ink films—often just 2-3 microns; however, screen printing deposits anywhere from six to 20 times the thickness of the other processes. This dramatically greater ink thickness is the cause of huge color variations and is a limiting factor for the screen-printing process. This sensitivity to ink-film thickness is one of the reasons simulated-process printing evolved.
Transparency, translucency, and opacity
On the one extreme we have perfect ink transparency in the form of four-color process; on the other, the very limited color mixing of 100%-opaque inks that require many, many printheads. Achieving perfect transparency or opacity is not possible, but you can design and control a wide range of translucent colors through simulated process—the perfect compromise between the extremes.
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