Abstract: A cable core, the interstitial spaces within which are being filled with waterproofing compound in a semi-fluid state as it passes through a compound-applying or filling chamber into which the compound is introduced under pressure, is advanced through a wiping die in a constricted passageway and into another chamber into which similar compound is pumped. The compound in the second chamber is at a substantially lower temperature than the compound in the filling chamber and exerts pressure radially on the cable core being filled to form a sheath or coating of the lower temperature compound around the filled core to seal the first compound in the core. The core is thereafter passed through a sizing die into a cooling chamber which solidifies the compound in and around the core. The cable core is thus conditioned for the subsequent application of sheathing materials thereto, for example, core wrapping and/or armor sheathing.