The reason for using different pulp grades is to achieve maximum stiffness for minimum weight. Fibre is the most expensive component of pulp cost, so a lot of effort is made to minimise fibre consumption.

Pulp grades produced and used in board production at Imatra:

• bleached birch pulp used for the top layer to give good printability, smoothness, and opacity without compromising strength properties
• bleached pine pulp used for the top and middle layers of packaging boards to give strength and stiffness
• unbleached pine pulp used for middle and back layers of packaging boards for liquid cartons to give strength
• spruce-CTMP (chemi-thermomechanical pulp) used for the middle layer of liquid packaging boards to give bulk and stiffness