b represents a case where the running conditions are bad but however where a relatively high negative pressure is able to provide a good runability the curve b u2032 represents a situation where some running conditions are good and some are bad and where a suitably increased negative pressure provides a good runability despite the bad conditions if the running conditions are very bad it is still possible in some cases i e depending on which running conditions are bad to achieve a good runability also below the curve b by increasing the negative pressure but this is not possible in all cases often the running conditions are such that the negative pressure should be controlled to be somewhere between the curves a and b in the intensified negative pressure region the negative pressure is controlled by control means according to a measured or in some other manner determined varying parameter such as the speed the dry solid contents the difference in the draw or the web tension the measurement information for observing the need for control and for setting the correct control level can be obtained to the control device e g from the process information on the other hand the need for control can also be observed by ocular inspection for instance a decreased web tension can often be detected by ocular inspection according to the invention the negative pressure levels can be controlled e g so that a desired difference in the draw e g 3 is obtained at the press whereby the paper characteristics can be optimised according to the needs of further processing the invention is.