Coated vs Uncoated paper in print
People often ask us about how coated and uncoated material each affect the look and feel of a finished document. I thought I’d try and explain some of the differences.
In the initial stages, most paper is made in a similar way, through drying, compressing and separating a dilute mixture of wood pulp, textile fibre, or recycled paper products. In industrial paper manufacture, the dried and separated material is treated and wound onto large rolls. The type and quality of the materials used in the manufacture, plus the manner of treatment during processing will determine the quality and feel of the finished paper.
The difference is the way that coated and uncoated paper is finished during manufacture
Coated papers are made by applying a fine layer of calcium carbonate, or china clay (or other material) to the surface of an uncoated sheet during manufacture. This coating process may be done once, twice, or three times, depending on how smooth a finished surface is required. The material will usually also be ‘calendared’, or milled smooth between hard rollers at the end of the process, to increase the sheet’s smoothness. Also, the material can be treated to provide different finishes – typically gloss, matt, or silk.
Adding coating to a sheet changes the nature of the paper in a number of ways. Because the coating is relatively denser than the substrate, the more coating there is on a sheet, the thinner it will be. So, for example, an uncoated 135gsm will be quite a stiff sheet of paper – thicker than the average corporate letterhead paper, but a 135gsm triple coated silk paper will thin by comparison, although both are the same weight. This is because more of the weight of the silk paper will be taken up by coating, which adds surface weight (but not thickness) to the sheet. For similar reasons, an uncoated sheet will often appear more opaque than a coated sheet of the same weight, since a disproportionately large part of the bulk of a coated sheet can be taken up by the coating materials themselves.
The more coating the smoother the paper
However, more coating added to a sheet generally means more smoothness, which generally means it will hold the detail and colour of fine screen litho printing much better. It will also enable a better colour range (shadow areas will usually appear darker in photos on coated materials) whereas on some uncoated papers imagery can look comparatively flat and lifeless. Unfortunately, for a printer, it is difficult to predict the results of four colour printing on uncoated papers without advance testing, as differences in how each brand is made can affect how each sheet will print. (This is far less the case with coated materials where the coating forms a fairly stable and predictable surface for the ink, no matter what is going on with the substrate.)
Different paper brands perform differently when printed
It is, of course, possible to make uncoated papers which give high-quality results for four colour printing – this material will generally be quite smooth and white itself, and the best ones can be quite expensive – often much more expensive than high quality coated material. The results of colour print on uncoated materials are often very pleasing – but it is a good idea to explore these issues with your printer before embarking on a major project.
So, in summary, coated papers will often give better colour reproduction than uncoated papers, but can feel much smoother and thinner. Uncoated papers will give a softer and more tactile quality but may raise questions about the colour reproduction.
Use our branded versus unbranded paper expertise to your benefit
With the detailed knowledge that we have acquired over several decades, we can help advise you about which kind of paper is going to be the right one for your print project.
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