Material Composition
The specific blend of virgin fibres and recycled content supplemented by chemical additives creates the functional profile for a particular grade of paper or board. High furnish quality indicates a high proportion of long, intact fibres and a low level of contaminants or fillers. This attribute directly influences the mechanical properties of the finished sheet, including its tensile strength and fold endurance.
Refining Impact
Mechanical processing in the refiner adjusts the length and fibrillation of the fibres to meet the needs of the end product. Over-refining can damage the furnish quality by shortening the fibres too much and creating excessive fines. These fine particles clog the forming wire and slow down the drainage of water on the paper machine.
A balanced refining process ensures that the internal bonds remain strong while maintaining the necessary bulk of the paper. Careful monitoring of the freeness value allows the mill to maintain consistency throughout the production run despite variations in the incoming pulp.
Recycled Content
Incorporating secondary fibres introduces shorter, weaker elements into the mix. Each cycle of recycling degrades the furnish quality as the fibres become brittle and lose their ability to form strong hydrogen bonds. Manufacturers often add chemical strengthening agents to compensate for the loss of natural fibre integrity in high-recycled grades.
