Thermal printer with a thermal head (16) for image-wise heating a heat-sensitive sheet (38) according to an elongate printing zone, transverse with respect to the sheet, and a rotatable print drum (15) for conveying such sheet past such thermal head while the head is urged towards the drum, which is provided with a pressure roller (17) for urging a sheet section, downstream of the printing zone, onto the print drum in order to establish a contact angle alpha between the sheet and the print drum. (FIG. 5)