offset printing press

Printing on uncoated paper is a whole different game than printing on coated paper. Because of the properties of the surface of the paper, uncoated paper absorbs ink much more readily than its coated alternative does. This poses its own unique set of challenges, but also comes with a number of benefits. Here are some tips for overcoming these challenges and getting the best possible result from printing on uncoated paper.

Separations
Colour separations need to be highly accurate for printing on uncoated paper. Halftone dots have a greater spread on uncoated paper because the ink soaks into it more. This is known as dot gain. Opening the separation helps you to achieve truer colour fidelity, and a brighter more detailed image as the size of the dot decreases and the space around it increases. How you do this will vary between areas of shadows and highlights, and different adjustments should also be made based on the colour of the paper.

Printing
Making the above adjustments should allow the press to carry more ink, so colour saturation, clarity and contrast will be greatly improved on uncoated paper. Ink colours for a wet press sheet should be increased by approximately five points to compensate for dryback. For both wet and dry press sheets, you should take density readings for reference further down the printing process or for the occurrence of re-runs.

Inks
It is recommended to use quick setting inks or process inks for uncoated paper, especially if back-up time is limited, because uncoated paper needs more drying time than coated does. Because of this, stacks should also be kept small to avoid offsetting. Between 500 and 700 sheets is recommended for uncoated printing. Adding fluorescent ink to the yellow and magenta process colours may also be beneficial. This can help to increase the brightness and clarity of the final product.

Paper
If you are using good quality uncoated paper, then it should be primed to balance ink holdout and ink receptivity. There is a variety of different qualities available on the market, so it is important to pay close attention to the manufacturer and grade of uncoated paper you are looking for when you buy. This can have a big effect on the quality of your printing.

Source: Paper Specs

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