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.
Hydraulic Pore Radius
Pore Dimension
Capillary structure governs how liquids move through the fibrous network of paper and board substrates. The calculated hydraulic pore radius represents the effective size of the channels that allow ink or water to flow into the sheet. This metric is derived from fluid flow rates.
Flow Dynamics
Liquid penetration in paper is often modeled using the Lucas-Washburn equation, where the hydraulic pore radius acts as the primary variable determining absorption speed. When a paperboard has a larger effective radius, it absorbs liquids more quickly, which can cause ink feathering or poor coating holdout during printing. Conversely, a very small radius slows liquid absorption and can lead to slow adhesive setting during high-speed packaging conversion.
Coating formulations use fine pigments to fill these surface pores and control the flow of ink solvents.
Substrate Density
Calendering and pressing during the papermaking process compress the fibre matrix to reduce the open volume. This mechanical action alters the hydraulic pore radius and increases the paper’s resistance to liquid penetration. Packaging grades like greaseproof paper or release liners require a minimal radius to prevent the migration of oils and silicones.
Mill testing validates these changes to guarantee consistent performance on printing presses and lamination lines.