Description ALSEAL Bitumen Flashing Tape is a black bituminous compound consisting of a self-adhesive polymer-modified bitumen layer coated onto a tough high-density polyethylene film and covered by an aluminum foil. It is economical, cold-applied instant flashing tape that is ready to use to waterproof with outstanding durability. Bitumen Flashing Tape provides excellent adhesion, improved heat resistance, tear and puncture resistance, and chemical resistance to chlorides, sulfates, alkalis, and acids.