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Print and Colour. All you need to know about Spec's but...
Have you ever received a printed job and wondered why the colour of your logo or corporate theme was not quite what you where expecting?
It's all down to the paper! Well, you would expect a printer to blame something, woudn't you!
There are broadly speaking three types of paper. Uncoated, Gloss and Matt. Within this there are a multitude of variations too, but let's stick to the basics first. Speaking to the end user and not to a graphic designer, who will advise you of this.
Uncoated papers have no added layer on the surface and are completely natural; however, the surface may be sized with starch. Uncoated papers receive their smoothness by calendaring, and are generally more absorbent than coated papers and are available in many different textures, colors, weights and finishes.
Ink soaks into the paper, precise halftone dots spread and deform. This is called dot gain. By opening the separation, actual dot size is decreased and the space surrounding the dot is increased. These adjustments allow the press to carry more ink, increasing color saturation, clarity and contrast.
Coated papers, in contrast, have a smoother finish, aren’t very porous and may be calendered or super-calendered off the papermaking machine. Ink will, more or less, sit on a coated paper’s surface and take longer to dry—producing sharper, brighter imagines because the ink doesn’t bleed into the paper and blur the halftone screen.
Coated paper: Coating produces papers with excellent ink holdout, which is ideal for color reproduction—detail is not lost and fine text holds up well—making them a popular choice for products ranging from books and magazines to annual reports and advertising supplements. Coated papers are often called art papers and are commonly found in glossy art books and textbooks containing photographs or illustrations. They have exceptional runnability and printability, as well as a consistently high-quality surface, stiffness, bulk and opacity.
Matt, Silk, Velvet, Smooth are just some of the variations on the coating theme and finish. They all have a slightly different level of smoothness, in simple terms. The finish is applied by Calendaring. This is in practice running the paper through (either on of off machine in the paper making process) a very large, smooth and heavy mangle. The higher the preassure the greater the gloss/smoothness level achieved.
So how does this change the colour?
The sharper the dot the more accurate the detail and colour. So the most accurate both in terms of colour match and detail will be achived with the gloss paper combined with the smoothest and highest quality level of coating. Most typical caoted stocks are double coated and are perfectly adequate for the majority of applications. Triple coated papers and boards are the most expensive and provide the best possible reproduction. These would printed at 175 to 200 Lines per inch as a rule with 2450 dpi.
Uncoated stock should be run at 133 - 150 Lpi as this gives more space around the dot, lets the light reflect back from the paper through the ink better and keeps the 'brightness' level up. otherwise the paper becomes saturated with too much dot gain as mentioned at the start.
The Flat look you get with uncoated papers is as a result of the less sharp dot and lower reflection levels of the raw material. A set of expensive Pantone books will show you this first hand, but as an end user you have to rely on your designer and/or printer to forwarn you of any potential pitfalls.
So next time your designer or marketing department insists on using some rather nice, but very expensive uncoated exotica, make sure you see the appropriate proofs first.
The next lesson will be spot colour, RGB and conversion to CMYK. Yes. I know, you can't wait!