Ink Holdout and Dot Gain When a Stock Changes Grade
Changing stock grades alters micro-porosity and light scattering, shifting ink holdout and dot gain, requiring immediate press curve and ink film adjustments.
Surface Energy Goniometry
Contact Angle
Liquid spreading behavior dictates whether a packaging substrate accepts a water-based adhesive or repels it entirely. Surface energy goniometry measures the static and dynamic contact angles of liquid drops placed on paper and board surfaces. Converters rely on this droplet measurement to predict printability and glue adhesion before production runs consume expensive substrates.
Drop profiles reveal the solid surface free energy of cellulose webs treated with corona discharge or chemical primers. Production lines maintain dyne levels within strict mill limits to prevent ink dewetting and delamination flaws on laminated cartons.
Dispersion Force
Polar and dispersive components combine to form the total surface energy calculation derived from multi-liquid drop testing. Intermolecular forces at the solid-liquid interface dictate wetting kinetics on coated offset papers and recycled linerboards. High dispersive values guarantee uniform fountain solution distribution during lithographic printing operations.
Low surface tension in the converting liquid allows rapid penetration into porous paperboard matrices without causing fiber swell. Laboratory technicians apply regression models to contact angle data extracted from polar and nonpolar probe liquids.
Wetting Boundary
Thermodynamic equilibrium dictates that a liquid drop reaches a stable contact angle only when solid-liquid-vapor interfacial tensions balance perfectly. Roughness and chemical heterogeneity across the paper web distort contact angle readings and require multi-point optical averaging. Substrates exhibiting surface energy below the threshold of the applied flexographic ink fail to retain solid fill definitions at high press speeds.
Coater operators adjust surfactant concentrations in aqueous barrier coatings to match the critical surface tension of the underlying paper substrate. Surface energy goniometry isolates the specific chemical fractions responsible for adhesion failure in coated packaging laminates.