Ink Passage
Void geometry quantification establishes the spatial arrangement of voids inside porous fiber matrices during converting operations. Pore throat distribution dictates liquid penetration dynamics across paperboard surfaces, controlling how fast aqueous coatings migrate inward under nip pressure. Mill engineers measure capillary constriction dimensions to predict varnish holdout during high speed offset runs.
Substrate permeability relies entirely on these interconnected pathways rather than total void volume alone. Narrow void dimensions restrict binder migration, keeping pigment particles on the surface for maximum gloss development.
Void Geometry
Capillary constriction analysis evaluates the geometric sizing of interconnecting pathways within cellulose networks. Porosity measurement protocols rely on mercury intrusion porosimetry to map constriction radii across dried board cross sections. Coating absorption rate depends upon the smallest constriction encountered along fluid migration routes.
Pressurized liquid transport through paperboard follows Hagen Poiseuille equations adapted for irregular geometries. Wide constriction profiles lead to excessive adhesive penetration during lamination, causing bond failure and surface starvation.
Permeability Limits
Fluid penetration thresholds define the maximum capillary pressure a dried paperboard coating can withstand before breakthrough occurs. Surface sizing formulations alter constriction frequency by depositing synthetic latex polymers across sheet faces. Converting lines adjust calender nip pressure to compress void networks when packaging specifications demand low air permeability.
High constriction uniformity prevents random ink absorption variations across offset press runs. Final print density depends directly on restrictive void dimensions halting solvent transport beneath the ink film.
