Juha Saari, Roger Bollström, Ken Mueller, Martti Toivakka

Abstract
The multi phase ink setting mechanism gives new insight into lithographic sheet fed offset ink modifi cations. The ink setting in sheet fed offset is by absorption and oxidation and the inks have a relatively high tack. Because of the wide variations in sheet-fed offset ink formulations the ink to paper interactions are extreme. The problems related to ink setting is mainly set-off (slow setting), mottling (ink setting variations), ink tack build up and surface strength problems (fast setting) and other print quality defects that can be caused by paper variations, print variations, slow/fast ink setting, dusting, base paper and coating structure, etc. The trend for more porous coatings with better whiteness, printed colour gamut, and light scattering properties will require ink modifi cation to control the ink setting phenomena. It is assumed that by changing the resins, solvents etc. of the printing ink, it is possible to adjust the ink setting in such way that the printing result is good for papers with different coating porosity volumes and porosity size distributions.

Keywords: Ink setting, Sheet-fed offset, Multiple-phase mechanism, Coated paper, Porosity
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Verónica Marchante, Francisco Martínez-Verdú, Elena Marchante, Juan Antonio Maciá, Elisabeth Chorro, Esther Perales, Vicente de Garcia, Jesus Inarejos, Susana Otero

Abstract
Nanopigments are a new type of pigment. They are hybrid materials consisting of organic dyes and layered silicate nanoparticles. Nanopigments are already applied to make polymeric coatings and they had shown improvement in mechanical, thermal and stability properties of the substrate and dyes (Batenburg and Fischer, 2001).

In this work, nanopigments had been synthesized to be applied in the manufacture of offset printing inks. Therefore, four different nanopigments are pursuit: cyan (C), magenta (M), yellow (Y), and black (K), in order to obtain primary colour for a four-colour-process system.

Keywords: Colorimetry, Nanopigments, Offset printing inks.
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Nina Deng, Frédéric Parent, Tony Manfred, Joe Aspler, Jean Hamel

Abstract
In the first report of this series, we characterized the draw variation of newsprint webs in a number of North American newspaper pressrooms using the technique of laser Doppler velocimetry. We showed that there is a good correlation between web break rates and pressroom draw variation. In this report, we have extended the draw variation study to commercial pressrooms, including heatset offset, coldset directory offset, and gravure printing. A wide range of draw variations was seen, likely related to the wide range of press operating and maintenance conditions. Also, as is the case with daily newspaper pressrooms, the contribution of paper is small. For a given draw variation, the web break rate in a heatset offset pressroom is significantly higher than that in newsprint pressrooms. This may be due to the fact that heatset offset presses are more complex. Case studies demonstrated that the draw variation can be reduced through improved press maintenance and operation.

Keywords: Runnability, Web Breaks, Tension, Offset printing, Gravure Printing
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