Mercury Intrusion Porosimetry ISO 15901 Dynamic Surface Absorption Inspection Protocols
ISO 15901-1 porosimetry paired with dynamic sorption testing qualifies coating pore structures to prevent back-trap mottle and ink setting failures on press.
Pore Diameter Distribution
Internal Structure
The network of air spaces within a paper sheet determines its permeability and liquid absorption behavior. A characterization of pore diameter distribution shows the range of different void sizes throughout the fibrous web. This property controls how coatings and adhesives are distributed when applied to the substrate.
Ink Interaction
Print quality on coated boards is highly dependent on how the liquid and pigment fractions of ink separate. A narrow pore diameter distribution prevents ink solvents from penetrating too deeply, keeping the color pigments on the surface for high print gloss. When the void sizes vary too widely, the ink is absorbed unevenly, resulting in a mottled print finish and poor image definition.
Control over this structural property is achieved by selecting specific calcium carbonate or clay pigment blends for the coating layer.
Pulp Processing
Refining processes in the mill break down fibres to create a denser sheet with smaller, more uniform pores. This mechanical treatment shifts the pore diameter distribution toward smaller sizes, which increases the paper’s resistance to gas and moisture migration. High-barrier packaging substrates rely on this fine pore structure to minimize the amount of polymer coating needed to achieve a barrier.
Lab testing with mercury intrusion porosimetry or liquid extrusion verifies that the production meets the required structural limits.