Caulking tubes made of cardboard are used to dispense caulking material, which seals joints and seams in construction applications. The caulking tubes are often lined with aluminum foil or kraft paper and spiral wound to increase the holding strength of the tube. The tube is typically inserted into a caulking gun and equipped with a plastic nozzle or spout and a plastic cap at the end.
Calking tubes are used in caulking guns for the administration of industrial adhesives and sealants. When pressure is applied to a caulking gun's trigger-like handle, a plunger forces the caulking out of the end of the tube in a controlled fashion. Some caulking tubes are already pressurized, and therefore do not require the assistance of a gun in order to apply caulk. Caulking tubes are mainly used in the construction industry to aid in sealing appliances in kitchens and bathrooms, tiling and cracks in window and door frames and along the joining of walls. Sealing any openings in walls, floors and ceilings increases the energy efficiency of a room or house and creates a watertight seal. Kraft tubes are also used to apply caulk to cracks and seams in boilers, piping and water vessels. As an alternative to plastic, paper tubes are not recyclable because their interior is hard to clean when it has been contaminated with the caulking epoxy material.
During fabrication, cardboard ribbons are coated with adhesives and wrapped at an angle around a mandrel. Many are also fiber wound. Most caulking tubes made of cardboard are spiral-wound with a thick core, to ensure they safely handle the pressure applied by caulking guns. These tubes have an interior lining of a non-permeable material and are filled with caulk, an epoxy paste material made of acrylic latex, butyl rubber, silicon, polyurethane or polysulfide. Caulk is usually white, but may come in different colors like black or beige for aesthetic purposes. After it has left the inside of the tube and is exposed to air, the caulk quickly cures and hardens. Caulking tubes are sometimes refillable as long as they are being continuously used and the caulk has not dried out. They must be disposed of after the caulk has cured. If used with a plunger, it should be large enough to scrape the tube interior walls; creating better friction fit so all the caulk comes out. Self-burping caulking tubes, however, are able to keep all air from coming out of the spout by creating a very small gap between the side wall of the tube and plunger, forcing any air to the side. Caulking tubes come in standard sizes to fit securely into a caulking gun's holster and to ensure proper operation of the equipment.