When a furnace shell cracks or an exhaust joint blows out, ordinary body filler chars and falls away within minutes. High-temperature putty is built for exactly this gap: a moldable compound that cures into a rigid, heat-stable solid capable of holding a seal where organic fillers cannot survive. What Makes a Putty "High-Temperature" Standard epoxy and polyester fillers rely on organic resin backbones that soften near 120 C and decompose well below 300 C. High-temperature putties replace or heavily load that backbone with inorganic material: silicate binders, ceramic powders, metal oxides, and reinforcing fibers. The cured mass behaves more like a fired ceramic than a plastic, so it keeps compressive strength and dimensional stability through repeated heating and cooling. Practical service ratings span a wide band. General cast-iron and steel repair grades hold to roughly 1,000 C (about 1,800 F). Specialized formulations for kiln furniture, molten-metal handling, and furnace doors are rated beyond 1,200 C. Flange and joint sealants trade peak temperature for flexibility, typically topping out near 500 C but tolerating pressure and vibration better. Core Advantages Heat resistance without a flame source. The putty is applied cold and cures at room temperature or with a modest bake, then withstands service heat far above its cure temperature. Gap filling and shaping. A stiff, non-slumping paste bridges cracks, rebuilds worn edges, and fills voids on vertical and overhead surfaces. Permanent set. Once cured, the repair does not re-melt, so a single application lasts through many thermal cycles. Chemical and oxidation resistance. Inorganic binders shrug off combustion gases, mild acids, oils, and the oxidizing atmosphere inside furnaces and exhaust systems. Electrical insulation. Many ceramic-filled grades are dielectric, which lets them anchor and insulate heating elements and terminals. Where High-Temperature Putty Is Used Furnace and kiln maintenance: sealing cracked refractory, rebedding elements, patching door seals, and filling gaps around thermocouple entries. Exhaust and flue repair: closing pinholes and cracks in manifolds, downpipes, and stacks where welding access is poor or the base metal is too thin to weld. Boiler and pressure equipment: sealing minor leaks around access doors, handholes, and flanged joints on the fire side. Metal casting operations: repairing cast-iron and cast-aluminum tooling defects before machining or coating, and patching launders and ladle covers. Industrial ovens and dryers: rebuilding worn hearth sections and sealing panel joints against heat loss. Power generation: patching turbine casing insulation covers, ducting, and heat-shield hardware. For components that need a continuous protective layer rather than a localized patch, a sprayable or brushable ceramic system may fit better. Our guide to high emissive ceramic coatings by substrate and service temperature covers that alternative. Email Us with your substrate and peak operating temperature for a putty recommendation. Incure's Epo-Weld High-Temperature Putties Incure produces a range of Epo-Weld high-temperature repair putties for demanding heat environments. Grades are available for cast iron and steel repair up to roughly 1,000 C, thixotropic pastes formulated for boiler doors and molten-metal contact at still higher temperatures, water-based aluminum repair compounds for cast-aluminum parts,…