OATEY 35503 Hercules® 8 oz. Regulary Body Furnace Cement

The Hercules regular body furnace cement is made for oil, gas, coal, and wood burning heating equipment, so it covers sealing jobs on furnaces, boilers, flue connections and stoves across those fuel types. It cures to a brown color and will not shrink, crack or crumble once set.

No asbestos, no oils and no silicon dioxide. The Hercules Clean 'n Friendly formulation meets or exceeds the OSHA requirement for minimal silica content, which is the usual reason institutional and school maintenance shops specify it over older stove cements.

Uncured Hercules furnace cement has a freeze point below +10 degrees F, so it tolerates a cold truck better than most water based compounds. Below that the uncured material can freeze, so pull it inside on hard freeze nights.

Model 35503 is the 8 oz can, listed at 0.026 volume and 1.125 lbs shipping weight. That size suits patching a flue joint, bedding a burner mounting plate or sealing a crack on a single unit. For multi-unit MRO work where you are sealing several appliances, order multiples or step up to a larger Hercules container.

Regular body is the standard trowel and putty knife consistency: stiff enough to stay in a vertical flue joint but still workable for filling gaps and cracks. It is a cement, not a flexible silicone, so it sets rigid and belongs on fixed joints in heating appliances rather than anywhere there is movement or vibration. For a joint that flexes, use a high temperature RTV instead.