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A high temperature caulk is a sealant often used in household and industrial heating systems as well as high temperature liquid pipelines. Created with heat-resistant silicone, the caulk is applied in the same manner as other typical caulk products. Once cured, it commonly dries to a pliable consistency while remaining flexible for long periods of time. Most types of high temperature caulk adhere firmly to metal, glass, ceramic and other commonly-found surfaces in the home and the workplace. The caulk also will commonly withstand temperatures from -80°F to 550°F (-62°C to 288°C) and will also survive intermittent exposure to temperature as high as 650°F (343°C).
When installing a new gas fireplace or furnace in a home, it is wise for people to use high temperature caulk in the joints of the flue pipe to reduce the chance of toxic fumes leaking into the living area of the structure. Besides sealing the exhaust fumes in the chimney, the caulk will also prevent flames from escaping through any joints or gaps in the pipe, which could lead to a fire within the structure's walls. Access doors on furnaces, expansion joints and damper seals are also key areas to apply the caulk. Within the home, oven doors and fireplace glass doors are also easily sealed against leaks with a thin bead of the caulk.
Industrial uses are gaskets in high temperature liquid pipelines and valves, as well as boiler lines and heat exchanging units. In some air compressor applications, the temperature of the compressed air line from the compressor to the holding tank warrants a thin coating of the high temperature sealant to prevent leaks. Using a typical caulk or sealant in this application could result in a premature failure and loss of air pressure, which could cause unproductive downtime for the workers. Most caulking will not adhere to galvanized metal, so it is important to understand the surface of the intended application.
High temperature caulk does not imply that the material is fireproof. Most types of this sealant will not withstand direct contact with fire or flame. The caulk is also not completely waterproof and will not cure underwater in most cases. The caulking does, however, require some atmospheric moisture to cure properly so it should not be used in areas that will be totally sealed off during the curing process. It is also important that the caulk not be subjected to continued oil, petroleum products or solvent in any application, or its effectiveness will be cut short.