How Paper Is Coated Calendered and Finished
Inline blade coating and soft-nip calendering establish surface uniformity, while targeted finishing passes balance visual embellishment against repulpability.
Air Knife
Metering Method
Coating application systems utilize a pressurized stream of gas to regulate the thickness of a liquid layer on a moving web. Use of an air knife allows for the uniform distribution of pigment across irregular surfaces without mechanical friction. This technique remains common in the production of carbonless papers and specialty art boards where surface contouring is preferred over a flat levelling effect.
Operational Mechanism
The process relies on a precision-machined nozzle that directs air at a specific angle and pressure toward the wet substrate. Adjusting the distance between the air knife and the paper surface determines the final coat weight by blowing back excess fluid into a collection pan. Higher line speeds typically require increased pressure to overcome the momentum of the coating liquid.
Because no solid component touches the paper, the risk of streaks from particles trapped under a blade is eliminated. This lack of physical contact permits the application of high-solid coatings on fragile or lightweight base sheets.
Surface Outcome
Boards treated with this method exhibit superior coverage on rougher base stocks compared to blade-coated alternatives. Because the air follows the natural topography of the sheet, the resulting film maintains a consistent thickness over peaks and valleys. This profile prevents the uneven ink absorption often seen when blades fill hollows with thicker deposits.