Abstract: A closed paperboard carton for containing hot foods includes an automatically openable vent responsive to presence of hot vapor emanating from the food to accommodate escape of the vapor. The vent comprises a tab portion formed in a wall of the carton, defined by at least a pair of equal-length knife cuts and having a region of connection with the wall. Vapors emanating from the hot food condense, and are absorbed by the inwardly facing wall surfaces of the paperboard carton. Absorption of condensed vapors in the region of the tab causes the inwardly facing surface of the tab to swell so that it curls outwardly and forms a vent. Once the vapor has substantially escaped, the inwardly facing wall surfaces tend to dry out, accompanied by uncurling of the tab to its original, vent-closing position.

Abstract: Paper webs are produced in a modified conventional felted wet press process in which the fiber furnish has a chemical debonding agent added thereto in high concentrations. The web (17) is formed on a conventional Fourdrinier wire (12), transferred to a moving felt (19) which presses the web against the surface of a drying cylinder (23) to reduce its water content, and is carried by the surface of the drying cylinder (23) to a creping blade (24). Liquid adhesive is applied to the surface of the creping cylinder (23) adhead of the contact with the web to provide substantial adherence of the web to the creping surface at the point of contact with the creping blade. The levels of addition of debonding agent to the pulp furnish and the amount of adhesive applied to the creping surface are selected such that the adhesion of the web to the surface at the creping blade is greater than the internal cohesion of the web.