Quantifying the Correlation between Ink Trapping Efficiency and Color Difference (ΔE_ab) in Offset Printing: A Predictive Model for Process Optimization

Abstract

This study establishes a quantitative framework for controlling overprint quality in sheet-fed offset printing, specifically examining the relationship between ink trapping efficiency and color difference (ΔE_ab). Using a laboratory IGT Orange Proofer on coated paper (200 g/m²) with standard CMYK inks, the research analyzes variations in optical density, ink film thickness (IFT), and colorimetric values. The results demonstrate that optical density and ΔE_ab follow a nonlinear quadratic relationship (R² ≥ 0.97), allowing for the precise determination of optimal ink density. Furthermore, the study identifies a strong inverse linear correlation (R² ranging from 0.91 to 0.97) between ink trapping efficiency (calculated via the Preucil model) and the ΔE_ab of secondary colors (Red, Green, Blue). These findings confirm that ΔE_ab serves as a reliable predictive indicator for trapping performance, offering a scientific basis for transitioning from density-based to colorimetric-based process control in compliance with ISO 12647-2 standards.