A calender for treating a paper web includes a roller stack being loaded with a load on one end. The calender has at least two hard rollers each having a substantially smooth outer surface. The at least two hard rollers each have a device for heating a surface of the roller to a temperature of at least 100.degree. C. The calender also includes at least two soft rollers, wherein each of the at least two soft rollers is disposed adjacent to at least one of the at least two hard rollers to form a working nip therebetween. At least one working nip has a dwell time of the paper web passing through the working nip of at least 0.1 ms. The load on the rollers produces an average compressive stress in the at least one working nip of at least 42 N/mm.sup.2. An arithmetic mean of the numerical value of the surface temperature T, the dwell time t and the compressive stress p in all of the working nips satisfies the following relationship: a target value Zg=1.378-0.00356.multidot.T-(0.00825-5.12.multidot.10.sup.-5 T)p-�0.039+(0.188-0.00112T)p.multidot.e.sup.-0.093p !t.multidot.e.sup.-0.42lt =0.8 to 0.9.