Nu-Calgon's 4293-75 Nu-Foam is an Expanding, Polyurethane, Prepolymer Foam that is used as a Sealant and Insulating Product. It is Designed to Seal, Fill, and Insulate Small Cracks, Gaps and Voids. Tack Free Time for Nu-Foam is Less than 30 Minutes at 70 F (21 C) and 40-50% Relative Humidity. It can be used to Seal and Insulate areas such as Openings Created for Refrigeration, Air Conditioning and Heating Tubes or Pipes, Duct Joints, Utility Penetrations in Exterior Sheeting, Masonry, Concrete or Wood Walls, and other Areas where Unwanted Air Penetration might occur