Method of making surface-treated paper

Claim 1

Method of surface sizing paper in the form of a continuous web, which consists essentially of passing the web over and in direct contact with a slot-shaped aperture in a container, which aperture is co-extensive with the width of the web, while continuously introducing into the container and exiting the same via the slot thereof a sizing material consisting essentially in an aqueous suspension of a sizing agent, continuously transferring the so-exiting sizing material without pulsations and without any excess, to the web passing said web over the surfaces adjacent the aperture at an angle of from 0° to 45° while under a controlled tension of at least 50 newton, said sizing material being introduced into said container at such a rate that the sizing material is applied to the paper web in an amount of at least (1.4 + 0.0107.B)cm 3 per m 2 of the paper web, where B = the surface roughness of the web measured according to Bendsten, and drying and reeling the so-sized paper web dried and finally reeled.