Fibre Characterization
Standardized laboratory microscopy and chemical staining identify and quantify the botanical origins and pulping methods used to manufacture paper products. A pulp furnish assay determines the exact volumetric and gravimetric ratios of softwood, hardwood, non-wood and secondary recovered fibres within a paperboard sheet. Laboratory analysts prepare diluted fibre suspensions on microscope slides and apply selective chemical stains, such as Graff C stain, Herzberg stain or Selleger stain.
Under polarized and transmitted light microscopy, chemical dyes react with residual lignin and hemicellulose, producing distinct colour shifts that differentiate mechanical, semichemical, unbleached chemical and bleached chemical pulps across diverse plant species.
Morphological Analysis
Microscopic examination relies on anatomical features such as fibre length, wall thickness, lumen width and cell wall pitting to identify tree species. Softwood fibres display prominent bordered pits and cross-field pitting, whereas hardwood furnishes reveal thin libriform fibres accompanied by broad vessel elements that indicate specific deciduous families. Analysts count individual fibres along predefined grid paths in accordance with standard test protocols such as TAPPI T401 or ISO 9184.
Weight factors multiply the counted fibre frequencies to convert numerical proportions into accurate dry weight percentages, compensating for mass differences between thick-walled summerwood tracheids and delicate hardwood cells. Chemical analysis measures ash content, alpha-cellulose purity and lignin content to complement the optical microscopic findings.
Procurement Validation
Commercial board buyers use furnish profiling to verify contractual fibre claims, confirm recycled content declarations and avoid illegal timber species. The testing detects the presence of unbleached mechanical fibres in cartons specified as solid bleached sulphate, revealing grade adulteration or recycled fibre substitution. Pulp furnish analysis cannot trace the geographic growth forest of a tree, which requires stable isotope or DNA testing methods.
Board converters rely on furnish data to optimize scoring, folding and tearing properties, because the ratio of long softwood fibres to short hardwood fibres directly governs sheet stiffness and tear resistance on packaging packaging lines.
