Investigation of lint particle adhesion in offset printing using Weibull statistics

Abstract

Linting is one of the biggest concerns for the newspaper printing industry. In the offset printing process, lint particles from the paper are removed from the paper surface under the force of the tacky ink, adhere to the printing blanket and disrupt the transfer of ink, causing deterioration in image quality and affecting the pressroom productivity. This paper deals with the bond strength of the lint particles released from the paper substrate and printing blanket surface. The strength distribution of lint particles was characterised in order to study the dynamics of linting. The dynamics was modelled using a system with two first-order rate equations. Weibull statistics were used to describe the particle size distribution of the lint collected after the sheet-fed printing trials. In this investigation, the lint samples were collected by washing the lint from the printing blanket, filtering and performing image analysis to measure the particles. In order to analyse the data, the lint particle size was set as an independent variable. The number of small particles removed is as expected much higher than the number of larger particles. When the ink tack is increased and thus also the force working on the lint particles, then the relative increase in large particles is higher than the number of small particles. The removal rate of particles from the printing blanket is independent of particle size indicating that both the adhesion force between particles and blanket and the removal force due to ink tack is proportional to the particle area.