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Accurately assessing the color quality of printed products becomes intricate when optical brightening agents (OBAs) are introduced in papers, as diverse interactions occur among different ink pigments and papers containing OBAs due to variations in ink formulation chemistries. Specifically, alkali‐based pigments, commonly used as spot colors, are carefully formulated to ensure consistency across production batches. The presence of OBAs, which absorb ultraviolet light and emit it in the visible spectrum, significantly affects color perception and accuracy on paper when interacting with these inks. This research marks an initial investigation into how OBAs in paper influence the color accuracy of five distinct alkali‐based spot color paste inks using a Little Joe ink proofer. The research examines the physical, optical, and colorimetric characteristics of two paper samples‐one with OBA and one without‐ and analyzes the colorimetric changes occurring during the ink drying process. The results indicate that reflex blue, purple, and violet spot colors achieved acceptable delta E (ΔE00) value of below 3 on non‐OBA paper, with rubine red being on the borderline at 3.1 after 48 h. In contrast, purple, rhodamine red and violet achieved acceptable ΔE00 below 3 on high OBA paper. The distinct behavior exhibited by certain inks led to the conclusion that achieving a consistent proofing procedure across diverse alkali‐based ink formulations is impractical. [ABSTRACT FROM AUTHOR]

Automated color measurement systems have become significant components of offset lithographic printing presses for better process control and reduced job waste. Some European press manufacturers are known to offer automated color measurement equipment that is confined to polarized density readings, which is uncommon in US. Introducing polarized densitometry into an environment where unpolarized densitometry is utilized can be problematic. Print professionals are on the lookout for a solution that is evidenced by a recent feature in a post from the IDEAlliance G7 Professionals forum seeking for a methodology to convert polarized to unpolarized readings. The present study applies the Bland–Altman method together with other statistical analyses to determine if a conversion between polarized and unpolarized densitometry can be established within a limited set of parameters. Three spectrodensitometers were used to record densitometric readings of wet and dry process inks on coated and uncoated drawdown proofs. The results showed that coated papers had significantly less variation between instruments compared to uncoated papers. Wet inks had more minor variations compared to dry inks. Furthermore, pure difference values and a Mann–Whitney U test indicated differences between unpolarized and polarized densitometric readings in all cases. Finally, t‐tests performed on the resulting difference data for both unpolarized versus polarized and unpolarized versus predicted polarized that showed fixed bias by means of the computed p‐values. [ABSTRACT FROM AUTHOR]

The appearance or printing quality of paper surfaces is mostly characterized by their glossiness, measured with a glossmeter as specular reflectance. The gloss properties of a base paper substrate can be improved after application of a poly(styrene-co-maleimide) nanoparticle coating under pure conditions or in the presence of different vegetable oils. The specular gloss properties of 11 different nanoparticle paper coatings have been determined under 75° and 85° incident light angles, with good relation between values along parallel (machine) and perpendicular (transverse) direction. The gloss properties for the different coatings have been further related to the surface topography. Therefore, the statistical and spatial surface roughness parameters have been studied in detail at two length scales including non-contact profilometry (1 × 1 mm2) and atomic force microscopy (2 × 2 μm2). Based on values of the Rayleigh parameter for non-contact profilometry, the surfaces can be considered as optically rough. The gloss values cannot be directly related to statistical surface roughness parameters. Otherwise, an experimental power-law model for gloss has been proposed as a function of (β/Sq) with correlation length β and root-mean-square roughness Sq. A best-fit model illustrates that gloss properties of various nanoparticle paper coatings mainly relate to the spatial surface roughness parameters determined from non-contact profilometry. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 596-610, 2016 [ABSTRACT FROM AUTHOR]

Paper properties, including the chemical or optical characteristics influence the quality and colorimetric characteristics of final printed colors. In this study, the effect of gloss, texture, and whiteness of the paper on the printed colors were investigated. The study was applied on 10 coated papers with different texture, gloss or whiteness, and the same grammage using two inkjet printers. It was found that the reproducibility of the printer can be affected with the paper brand, and this effect is statistically dependent on the brand of printer. The kind of paper significantly influences the light fastness of the final printed colors, and this effect statistically depends on the printer. Although, the paper's properties such as gloss and whiteness affect the gamut volume, it is not totally possible to model this effect. The effect of paper on the colorimetric values of the final printed colors is statistically significant. However, the influence of the brand of printer on the color changes via the paper difference is not statistically provable. Edge frequency technique was introduced as an appropriate method for computing texture properties of papers. The texture difference computed by this method shows a suitable correlation with the color differences caused by changing the paper's texture; however, it depends on the printer's brand. Furthermore, there is a good correlation between the Edge frequency difference and the gamut volume variation for papers with different texture while the other parameters such as gloss and whiteness are the same. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 284-291, 2013 [ABSTRACT FROM AUTHOR]

Nowadays, effect pigments are widely used in many printing industries. The colorful effects produced by light scattering of these types of pigments add an additional value to the prints and enhances the overall quality of color appearance. The aim of this study was to investigate the quality enhancement of printed specialty papers with various effect pigments in combination with offset inks. Four different effect pigments were used (one luster pigment-EP1, two interference pigments-EP2, EP3, and one multicolor pigment-EP4) as well as two types of paper substrates (film synthetic paper and wood-free paper). The effect pigments were overprinted on dried CMYK offset prints on both paper substrates. The following analysis were performed: scanning electron microscopy analysis of effect pigment particles, contact angles of papers and offset prints, Fourier transform infrared spectrocopy (FTIR), principal components analysis (principal components analysis (PCA)), and flop index analysis of overprinted effect pigments, and paper and print gloss. The results of the experiment indicate that effect pigments behaved differently on different printing substrates. From the FTIR and PCA, it was found that the different composition of effect pigments differently influence the behavior of these particles on the final prints. Effect pigments overprinted on offset CMYK inks on both paper substrates enhance print gloss, except interference pigment EP2 on film synthetic paper. It was also found that the ink color has the most pronounced influence on flop index, followed by the papertype and the type of effect pigment. Higher flop index was obtained at wood-free paper, especially by overprinted pigment EP2. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 168-176, 2013. [ABSTRACT FROM AUTHOR]

Consumers' tolerance of the color of recycled paper was evaluated by the visual assessment of such paper by 30 Japanese university students. The assessment was performed to measure color tolerance using 266 color samples in eight conditions specifying the situation of paper as (1) 'either paper is recycled or not recycled,' (2) 'whether you will buy/use,' and (3) 'use for office paper or for workbook paper.' The responses of the subjects were sorted out quantitatively in terms of the colorimetric values of color samples and then correlated with International Organization for Standardization (ISO) brightness and CIE whiteness. Both the ISO brightness and CIE whiteness were found to be dependent on hue factors and also to be restricted for use in direct representation of the consumers' responses to paper quality. Since the consumers' evaluation of paper quality is due to visual whiteness, we propose a new equation to predict the consumers' tolerance of paper color, in which the equation contains two factors concerning the color distance from the white point and the hue impact. The new tolerance equation was confirmed to predict the consumers' tolerance successfully, particularly when the consumers are aware that the paper is recycled. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011 [ABSTRACT FROM AUTHOR]