Different batches of coated papers of the same type and GSM from the same paper mill can show differences in printability with the changes in coating formulation. This work studies the papers and paperboards from a few paper and paperboard mills.
Different types of latex binders were tried in pre-coat and top-coat in paper manufacturing. A specially designed ‘print test forme’ was printed under production conditions in the same print run on a Heidelberg CD 102 sheetfed offset press using CtP plates and 4-color Huber Micro Inks Perfektion F series process inks. During the same run each type of paper was first printed with the correct ink-water balance and then with the dampening solution feed increased to 100% to study its effect on printability.
To realise the objectives and the research methods mentioned above a list of was drawn up as follows. A special test forme, see figure 1, was designed to study all the parameters.
Important parameters from the printers’ point of view –
Print density, Dot gain, Print contrast, Trapping in multicolor printing, Hue error, Grey error, Gloss, Lab values, Delta E on different papers, Mottling, and Set-off.
Important laboratory tests –
IGT dry pick, Stain length, Paper gloss, Print gloss, Delta gloss, Brightness, K & N, Set-off, Mottle index papers
Print Production Trials
Laboratory test parameters
Print performance inference through laboratory tests and production print trials
1. Print density trend in laboratory evaluation matches print production trials.
2. Density trend in porometric test is also reproduced in print production densities.
3. Back trap mottle (BTM) trend in laboratory is found to be in line with print mottle in print production.
4. Water interference mottle (WIM) in laboratory is found to be in line with print mottle rating of print production trials.
5. Set off density trend for SBR products are in line with mottling index for the production printed sheets. Lower set off values gives lower mottling tendencies.
Papers and paperboards for the investigations were kindly supplied by BILT, JK, ITC, NR Agarwal, Gayatri, Balakrishna mills. Huber Micro Inks supplied the inks and Jasmine Art Printers, Mumbai allowed the carrying out of all print production trials. Laboratory tests were conducted at Apcotex Industries, Mumbai.