Forming of LWC Base Papers, 1997 Papermakers Conference Proceedings

The development of the formers on LWC base paper has gone from Fourdriniers to hybrid formers to gap formers during the last 20 years. In the late 1980’s it could be seen from newsprint machines that gap formers had excellent quality and runnability potential. So the use of gap former technology for LWC was an obvious choice. However LWC base paper had its own strict requirements for good basis weight profiles (no streaks), no holes in paper (cleanliness) and high internal bond strength (heatset-offset printing). It was also desirable that formation would be on a good level, there wouldn’t be pin holes in the base paper and base paper surfaces would be smooth and symmetrical for coating. Many pilot machine trials were conducted to develop a roll and blade gap former, SpeedFormer, to meet these requirements. Today there are eight SpeedFormer references running on LWC base paper and two more will be start up in the beginning of 1998. The hybrid former, SymFormer MB, is a good alternative for a small rebuild. The hybrid former technology can compete with gap formers, when the paper machine is slow (900- 1000 m/min) and narrow. However generally the quality and the runnability properties are better with a gap former than a hybrid former.