a method and apparatus for forming a web having a predetermined grammage profile in its transverse direction is provided . the method includes the steps of introducing a composite flow of particulate material suspended in air into the distribution chamber of a forming head and depositing the material on the upper surface of an air permeable belt while applying suction to form a web and while the grammage profile is controlled by measuring the profile of the web downstream of the distribution chamber , comparing the measurement with predetermined set points , generating a control signal representative of any detected difference and controlling the amount of suction applied in predetermined suction sections in response to the control signal so as to provide a web having a predetermined grammage profile . an apparatus for accomplishing each of the steps of the method is also provided .