Patent ID: 8425721

Claim:
A method for treating a fibrous web with a liquid in a wetstack calender of at least three nip forming structures, the method comprising the steps of: forming a liquid spray chamber between a first spray box and an adjacent first nip forming structure having a first movable surface and a second nip forming structure having a second movable surface, which first and second movable surfaces form a first nip of the wetstack calender; guiding the fibrous web supported by the first movable surface of the first nip forming structure into the liquid spray chamber and into the first nip wherein motion of the web into the first nip defines a first direction; spraying with spray nozzles, positioned by the first spray box, treatment liquid onto a surface of the fibrous web while the web is supported on said first movable surface, and spaced from the first nip in a direction opposite the direction defined by the motion of the web into the nip; removing air or treatment medium mist from the liquid spray chamber; after spraying treatment liquid onto the surface of the fibrous web pressing the fibrous web in the first nip; forming a second liquid spray chamber between a second spray box and a surface of the fibrous web which is supported on the second nip forming structure or an adjacent third nip forming structure which is mounted for movement; forming a second nip between the second nip forming structure or the adjacent third nip forming structure with a fourth nip forming structure of the wetstack calender; guiding the fibrous web into the second liquid spray chamber and into the second nip; spraying with spray nozzles, positioned by the second spray box, treatment liquid onto the surface of the supported fibrous web spaced upstream from the second nip; removing air or treatment medium mist from the second liquid spray chamber; and after spraying treatment liquid onto the surface of the fibrous web pressing the fibrous web into the second nip; wherein the first, second, and fourth rolls form at least part of the wetstack of at least three rolls.