Linting

Linting is a problem which has always concerned the papermaking and printing industry.  In the offset printing process, loose fibres and fines from the uncoated paper adhere to the blanket and disrupt the transfer of ink.  This reduces the print quality and is a major effect on the pressroom efficiency.

Linting is complex because it is a dynamic process that is influenced by both the printing press and paper variables.  The lint particles continuously move on and off the blanket, either transferring back to the paper or to the printing plate or into the ink and water systems – making it difficult to measure lint reproducibly. This is why the lint measured after any printing trial from the blanket is only part of the lint that has been removed from the surface of the paper.

Our research has been investigating the dynamics of lint migration during offset printing to measure the rate of lint transfer and to gain understanding how it relates to the paper properties and printing press variables.  This work was done using a high speed video camera combined with image analysis techniques.  Figure 1 below shows the captured image of lint build-up during a press run, while Figure 2 shows threshold results from dynamic and static images after performing image analysis.

Lintcam

Figure 1. An Example of lint build-up captured by the lint camera during a press run. (A) Dynamic images at the very beginning of run; (B) Dynamic images at 500 copies; (C) Dynamic images at 7000 copies.  Press speed was 8000 copies an hour.

lintcam2

Figure 2. Dynamic (top row) and static (bottom row) images of 45gsm newsprint after printing 7000 copies at tack 12.5 acquired by the lint camera. (A) Raw image of an analysed area; (B) Image after applying manual threshold to the dynamic and static images in (A). Note: static images were taken at the end of run, after the press is halted.

This research has been supported by the Australian Research Council through Linkage grants, Monash University and Norske Skog, which is the only Australian manufacturer of newsprint and related grades.

Selected Publications

Lestiani, R., Batchelor, W., and Banham, P. (2014). Effect of paper and printing press variables on the rates of adhesion failure in the linting of offset printingJournal of Adhesion Science & Technology28(19), 1935-1948.

Lestiani, R., Batchelor, W., and Banham, P. (2013). Investigation of the performance of a lint camera system in identifying lint using image analysisAppita Journal66(4), 299-305.

Batchelor, W. and Sudarno, A. (2010). Characterisation of lint particle removal in offset printing with weibull statisticsJournal of Adhesion Science & Technology, 24:619.

Batchelor, W.J., Sudarno, A., Gujjari, C., and Banham, P. (2009). Fundamental studies of linting in the offset printing of newsprint, Transactions 14th Fundamental Research Symposium, I'Anson, S.J., Ed., Fundamental Research Society, Oxford, p.1325.

Gujjari, C., Batchelor, W., Sudarno, A., and Banham, P. (2009). The relationship between tack and linting in the offset printing of newsprint gradesTAPPI J.8(8):4.

Sudarno, A., Batchelor, W., Banham, P., and Gujjari, C. (2007). Investigation of the effect of press and paper variables on linting during the offset printing of newsprintTAPPI J.6(9):25.

Voltaire, J., Batchelor, W., Fogden, A., Sudarno, A., and Banham, P. (2007). New technique for monitoring ink-water balance on an offset pressAppita J.60(2):120.