Industrial-scale rotogravure printing tests

Today 15 to 20 % of printing is achieved through the gravure technology. In Europe, Germany is far ahead in the number of gravure printing units with approximately 100 roto-gravure printing machines. Then come Italy with 40 printing machines, United Kingdom, France and Holland with nearly 20 for each of them. Gravure printing technology requests super-calendered or LWC papers. The width of the paper reels of the most recent printing units is larger than 3.0 meters. Gravure printing has, as well as lithography its specific printing defects. Missing dots is one of the best known problem in gravure printing. Other problems such as whiskering, ghosting, lack of printing gloss, printing unevenness in half tones and solids areas are also disturbing the achievement in printing quality. Although different laboratory tests such as Heliotest, Winstone press characterize the quality of the paper before printing and try to forecast the printing quality, it is clearly shown that the laboratory printing prediction does not always fit with the industrial printing results. Industrial printing trials have been specifically developed to make it possible to evaluate right printing possibilities of papers. A specific printing form test is available to characterize print unevenness, missing dots, printing gloss in the different colours. The influence of the printing conditions (ink viscosity, printing speed, electrostatic assistance) on the print quality is studied. A graduation in the quality linked to the missing dots and print unevenness is realised through a collection of industrials printed papers. The industrial printing trial developed is today an absolutely necessary tool to realise a real diagnostic of the printing quality for gravure papers.