Folding Board
Smoothness versus Bulk
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Every board producer knows how important is to get the highest bulk possible for its folding board. This is because the strength depends very much on this property, but smoothness, which determines the quality of the printing surface, is just as important as bulk. In most cases the solution is a compromise between smoothness and bulk. Smoothness is obtained in the process by a hard nip calender. While the calender gives the smoothness required, it often reduces the bulk. Another very important factor for achieving good smoothness is the moisture level of the board when it enters the calender. This moisture level is another factor that can reduce the thickness in the calender nip. |
Consequently, the question is: How can we improve the smoothness without losing thickness? Or: How can we improve the smoothness and at the same time reduce the pressure of the calender to get better thickness? The answer to these questions is to get the correct moisture on the surface of the board you want to treat. It is well known that increasing the moisture content of fiber material lowers the glass transition temperature of the wood polymers. This allows the calender to develop a smoother surface. Page 1 of 3 |
