Acoustic emission and tack of heat-set inks during setting on MWC-papers and fountain solution emulsification

To investigate the relationship between ink film splitting noise and ink tack, two tack-measuring devices were monitored by a microphone. The first of these was the Deltack® (Prüfbau), to study tack build on paper, and the second was the Hydroscope® (Testprint), measuring ink tack change with fountain solution level. Three medium weight coated (MWC) papers and two heat-set inks of differing tack and emulsion capacity were analysed. It was concluded that acoustic average power is a consequence of cavitation and flow mechanisms, and not necessarily linked linearly to tack. The Hydroscope measurements usually gave decreasing tack, average power and average frequency with increasing fountain solution concentration; however fountain solution droplets can also act as an extra sound source. A relation between average frequency and droplet size was postulated. The results demonstrate the sensitivity of the acoustic method and support its implementation for further studies in the field.