Inks and Separations
Traditional printing methods require artwork to be translated to printing plates, one plate for each ink that will be used to produce the final images/type. While separations have long been the responsibility of the print shop, modern graphics software has given the designer the ability to greatly control separations.
While design work may not be directly performed by many of our clients, a basic understanding of inks and separations can help you with some of your print planning, and maybe even spark some ideas.
Overview
Traditional presses and in most cases, modern digital print machines both rely on a fundamental principle of applying single inks in succession to a sheet of paper so that the inks may at times combine visually to create particular effects. The variation in whether the ink is applied as a solid (100%) shape, or in tiny dots of varying size, is what allows us to print the countless elements that could make up a printed page: text, artwork, images, etc.
Standard Inks
The most commonly used library of inks is the Pantone Colour Matching System (PMS), which is a sort of recipe book for printers to create specific ink
Looking at the application of a single ink to the page (in this case, a dark blue) we find a couple standard variations in style:
Even though they appear different, each style demonstrates the use of a single
Next, we can add a second ink (a medium red) and vary the ways these two interact:
In the first three, the shapes may touch but are still discreet. But the fourth style, duotone, has the inks interacting and appearing to make a third
Process Colour
Recreating
There are also “Hexachrome” presses, which add orange and green inks to CMYK (yes, making CMYKOG). This broadens the gamut of colours that can be effectively reproduced but requires a specialty press. Another method that improves printing results is adding two lighter inks, cyan and magenta (CcMmYK) to the gamut. This is found in some retail printers designed for high-quality photographic output.
Example
Here is our original image of an attractive bird:
But what if we’re only printing with two inks, such as black and a corporate blue? Well, we can make a duotone image that uses the blue ink to accentuate the bird photo.
This is a brief demonstration of how print technology is quite flexible and that in planning a print job, there are options to consider in choosing what inks to use
Separtion
The method of creating printing plates for each ink that will be used is aptly called separation. Using our process colour printed bird photo from above, the CMYK separations would look something like this:
Each printing plate (four in total) would have the necessary dots so that these inks, when printed over top each other, will produce an image that appears like the original.
The grayscale (black only) image would just have one plate while the duotone image would have two. There are also tritone images, quadtone images, and so forth.
RGB Colours
There is a fundamental physical difference between printing inks, as described above, and the
With ink, you typically start with a white page and add inks to make colours. With light, you start with an absence of light (black) and add light through the spectrum to white. So, for example, an image that is RGB may appear the same as one that is CMYK, but before it can be separated for ink plates, it must be converted to CMYK.
This creates challenges for the modern, digital design process. There has to be some compromise between the degree to which ink printing is able to render colour and how much ‘predictability’ there is for the designer using a computer to “get what she sees” — for the final printed piece to resemble how it looked on screen. It is a challenge both ways, though, since a computer screen cannot display such print effects as metallic inks, foiling, embossing, etc.
Needless to say, this is a complicated arrangement that provides no end of study. For the purpose of this article, it is simplest to advise that not all screen colours can be printed exactly and that the planning of inks and separations on a computer requires some conceptualization of what will happen at press time.
Digital Printing
A digital printer will still typically use either one ink/toner (such as with a black laser printer) or four (CMYK for most
Summary
The computer has been smartly integrated with print technology but will always provide certain challenges due to some of the fundamental differences between the two. Planning a print job on a computer, so that the eventual separation of
