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.
De Inkability Score
Surface Porosity
Measurement of liquid absorption capacity defines the resistance a substrate offers when facing ink penetration during a lithographic process. The de inkability score quantifies how effectively a specific deinking process removes toner or solvent based pigments from paper fibres during the recycling stage. High values indicate that a paper grade retains its physical integrity while releasing printed contaminants into the cleaning solution without excessive fibre loss.
Testing requires standard pulping protocols followed by flotation cycles that isolate detached ink particles from the slurry. Technicians calculate the results by comparing the light reflectance values of the original paper stock against the recycled sheets produced from the pulped samples. This metric holds clear limits because it applies exclusively to chemical and mechanical deinking methods on cellulose substrates.
Chemistry Calibration
Chemical surfactants and mechanical agitation influence the efficiency of ink detachment from the fibre surface. The de inkability score shifts according to the specific particle size distribution of the initial print and the binding agent used in the commercial ink formulation. Water soluble inks often generate higher removal rates than heat set equivalents because the former disperses more readily during the initial pulping phase.
Mills adjust the pH level of the wash tank to optimise the release of particles while preventing the ink from reattaching to the clean fibres. Heavy coatings on packaging board interfere with this detachment and reduce the total yield of the recovered pulp. The process stops when the flotation cell fails to capture remaining pigment particles that have bonded too strongly to the surface of the base sheet.
Performance Expectation
Industrial recycling facilities rely on the consistency of this measurement to predict the quality of secondary fibre streams entering the production line. A predictable de inkability score allows operators to maintain stable brightness targets in finished paper products without frequent changes to bleaching agents or process timing. Manufacturers prioritize substrates with high scores to avoid the accumulation of dark specks in the final sheet.
Consistent batch performance reduces the quantity of reject material diverted to landfill during the wash cycle. High scores indicate an efficient compatibility between current print technologies and sustainable waste management protocols.