Miroslav Hoc

Abstract
In newspaper production dusting or linting is one of the most troublesome problems associated with the surface of paper. During offset printing dust and fibre particles leave the paper surface and adhere to the printing blanket. These lint particles will eventually cause deterioration in the printed image, and the printing cylinder must be cleaned. This cleaning process takes time, costs money and will create health hazards, so printers are keen on reducing lint build-up. Linting is a phenomenon caused by the interaction between printing press and paper. The mechanism of linting is generally described as a combined effect of the ink film splitting forces and the inter-fibre bonding energy in the paper surface.

A dynamic On-Line Linting Measurement System (OLM) has been developed. The build-up of lint on the blanket is measured dynamically during the ongoing printing. The OLM test printing emulates a commercial printing, this although it is carried out in the laboratory. The OLM-technology is a way of carrying out dynamic linting studies even with a small amount of test material, while at the same time retaining the effect of the variables of the printing process on the lint transport. Measurement of lint circulation by the OLM-technology makes it possible to judge whether the build-up of lint on the rubber blanket is caused by the paper or is due to the printing conditions. Both the paper-maker and the printer have obtained an extraordinary tool for studying the reasons for the build-up of lint.

Keywords: Linting, Newsprint, Test methods, Paper properties, Offset printing
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Christine Canet, Michel Martineau, Valériane Vigne

Abstract
Lint is a secular and critical problem for printers. Even if numerous methods exist to predict paper tendency to create lint, none of them permits to defi ne its impact on print quality. Even if all papers tend to create lint, not all forms of lint are equally problematic for offset printers. This paper describes main results of an applied project conducted at the Institute aiming to develop a methodology predicting the lint impact on print quality and its severity for printers.

Keywords: Printing, Offset, Lithography, Quality control, Paper, Lint, Image analysis
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Erik Bohlin, Ludovic Coppel, Caisa Andersson, Per Edström

Abstract
Polyester films were coated with a coating colour based on a ground calcium carbonate with narrow particle size distribution. Four different coat weights were produced. The coated sheets were calendered and the samples were exposed to up to twenty nips in the calender at a line load of 300 kN/m at 50°C. The brightness and the thickness were measured after each calendering nip. Reflectometry was used to measure the refractive index and the microroughness of the samples. Calendering lead to a decrease of the Kubelka-Munk scattering coefficient and an increase of the absorption coefficient of the coated transparent films. Taking into account non-uniform surface reflection at the boundaries between media of different refractive indices, a large part of the reflectance decrease due to calendering could be attributed to an increase of the effective refractive index at the coating surface and a decrease of the surface microroughness.

Keywords: Coating, Calendering, Gloss, Brightness, Refractive index
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