It’s pretty important to keep in mind the physical make up of uncoated papers when planning your print project. By nature, uncoated papers are absorbent, so inks or anything that acts like an ink- varnishes and coatings – will react differently on an uncoated sheet than they would on a coated paper. Pressroom technology has become highly sophisticated and as such allows designers and production managers the ability to use more premium uncoated papers in new ways.
Well planned separations are critical for a successful uncoated printing job. Remember on an uncoated sheet, inks will soak into the paper more, halftone dots can spread and deform – this called dot gain. By opening up the separation, the dot size is decreased and the space surrounding the dot increases. This allows the press operator to run normal ink densities resulting in truer color fidelity, image brightness and detail. Opening the separations allows the use of finer line screens 175-200+.
Factors to consider when opening up separations:
• Paper surface
• Type of press – conventional or UV
• Blankets and plates
• Screen types – conventional or stochastic
• Original image – lots of shadows, bright colors
• Expectations – does the client want a sharp, crisp look or a softer feel
Make sure to consider the paper shade when reviewing color proofs. For warmer stocks like a natural white or cream, you may want to reduce yellow – especially in skin tones. On a sheet that is more blue white, you might want to reduce the cyan. Scanning is the best place to do these types of changes. If possible, ask the printer to proof on the actual paper stock so you know the exact effect the shade will have on the printed image.
Printing on an uncoated sheet should not pose any more challenges than a coated paper if the separations are properly prepared. These adjustments allow the press to carry more ink and increase color saturation, clarity, and contrast.
After a wet press sheet is approved, all inks should increase by 5-10 points based on densitometer readings – this will compensate for dryback.
When it comes to inks recommended for uncoated sheets, process inks or quick setting inks are recommended. Uncoated paper usually requires a bit more drying time than coated, so keep the stacks small – around 500-700 sheets – this will help prevent offsetting.
Depending on the image, you may want to add more fluorescent ink to the magenta and yellow process colors. They tend to increase the perceived reflected light on the surface, increasing brightness and clarity.
Hopefully these tips will help you the next time you have a print project that you’d like to use an uncoated paper for. They really do impact the overall feel of the piece, for more information or to see samples on uncoated papers, please contact our sample department.