PAPER AND PRINT CHARACTERISTICS OF HIGH-QUALITY GRADES - HOW TO ACHIEVE THESE WITH MODERN CALENDERING TECHNIQUES

The traditional method of calendering to achieve high surface qualitie s is the supercalender. With modern supercalenders, the floating stack principle and nip relieving are two important features for enhancing calendering potential and improving machine line force profiles. Soft calenders in an-line operation are an economic alternative to supercal endering. Pilot plant trials and commercial production show that soft calenders with two nips can be used for calendering SC-B papers and co ated art papers. The calendering potential of soft nips was also teste d for SCA grades. Virtually supercalender smoothness was achieved and print gloss was even exceeded. But in gravure printing missing dot ass essment of continuous and quarter tones was not fully satisfactory. Re sults in offset printing, however, were even superior to the supercale ndered paper. Test results with LWC offset showed that surface quality of the supercalendered paper can be attained with four nips, even on- line with the coating machine.