Copyright: © the author(s), publisher and licensee Technoscience Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited International Journal of Scientific Research in Science and Technology Print ISSN: 2395-6011 | Online ISSN: 2395-602X (www.ijsrst.com) doi : https://doi.org/10.32628/IJSRST229544 235 Effect of Ink Transfer on Color Values in Lithographic Printing Tran Thi Thu Trang, Luu Bach Hiep, Hoang Thi Kieu Nguyen School of Chemical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam Nguyen.hoangthikieu@hust.edu.vn Article Info Volume 9, Issue 5 Page Number : 235-239 Publication Issue September-October-2022 Article History Accepted : 10 Sep 2022 Published : 25 Sep 2022 ABSTRACT The effect of ink transfer on color parameters of primary and secondary solid inks was investigated for a commercial lithographic printing system. The ink transfer is evaluated through color density values and ink trapping factors. The results indicate that the targeted color values can be obtained by density control. The standard color values according to the ISO 12647-2:2013 are set up in relation to the ink densities. Keywords : Lithographic Printing, Ink Trapping, Ink Density, ISO 12647-2 I. INTRODUCTION In the process of multi-color offset printing, a paste ink of a given color – yellow, magenta, cyan, and black (CMYK) is transferred from the ink fountain through the series of inking rollers, the image areas of the plate (image carrier), the blanket, and to the paper. This ink transfer determines the dot size, ink trap, and ink film thickness, primarily in tonal and color variations. Density measurements of solid ink CMYK patches are used to monitor the ink film thickness applied during a press run. The ink density values influence dot gain, print contrast, and apparent trap [1, 2]. Ink trapping is defined as the amount of the second ink transferred on top of the first ink during the multi-color printing process [3]. In the printing process of pasty inks, such as lithography, the upper ink layers are never trapped with the whole layer thickness compared to printed directly on paper. Hence, the ink trapping is evaluated or measured in terms of percentage. A high percentage is "good" because it gives the desired color. A low percentage, which gives uneven or off-color, is "poor". A poor percentage narrows the printable color gamut and may cause image problems [4]. In multi-color lithographic printing with CMYK inks, the CMYK ink densities must be in balance. If ink densities are not in harmony, the color (hue) of the Red, Green and Blue (two color overprints) will shift. This balance depends on both ink film thickness and ink trapping. Therefore, monitoring solid ink density during a press run is essential when comparing any printed material in terms of quality [1]. However, in almost standards, the colors of solids are standardized by CIELab values, for example, ISO 12647 [5]. A matching ISO 12647 solid color can be archived with very different densities that induce different dot gain curves. Therefore, the standard color values should be connected to color densities in