Abstract: A porous web material for making infusion packages having enhanced mechanical seam integrity is obtained by treating the entire fibrous web material with an aqueous emulsion of a hydrophobic agent selected from the group consisting of high molecular weight cross-linked acrylic polymers, silicones, fluorohydrocarbons, paraffins, alkyl ketene dimers and stearylated materials. The hydrophobic agent, which may also act as a strength imparting binder, is preferably applied as a saturating treatment. The treated web is subsequently dried to insolublize the agent on the web. The web exhibits no appreciable water climb when measured using water at a temperature of about 100.degree. C. and no substantial loss of infusion characteristics while providing less than 10 percent failure in a mechanical seam therein when exposed to boiling water.