Fiber Coarseness

Measurement Technique

Optical analysis instruments measure this value by scanning dilute pulp suspensions to count individual fibers and calculate their total length. The dry weight of the scanned fiber sample is then divided by the aggregate length to yield a value usually expressed in milligrams per hundred meters. Modern laboratory systems use polarized light and image analysis to differentiate fibers from vessel elements and debris.

Accurate determination of fiber coarseness allows mills to optimize their refining energy because the property directly affects how fibers conform to each other in the wet web. Low values indicate flexible fibers that bond easily, whereas high values correspond to stiff fibers that create a bulky, porous sheet.

Product Performance

Paperboard converting operations rely on specific fiber characteristics to maintain sheet stiffness and printability. A furnish with high fiber coarseness provides high bending resistance, which is desirable for heavy folding cartons. However, this same high value can lead to a rougher sheet surface that requires extra coating to achieve a high quality print finish.

Sourcing decisions must weigh the need for structural strength against the demands of the printing process.