BOSS - 03422BK10 - 139 Hi-Temp Mortar, Black

Item Number: BOSS13910  MFR Part Number: 03422BK10


Hi-Temp Mortar, Standard Cartridge, Black
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Boss® 139 Hi-Temp Mortar Is A Non Combustible Silicate Cement That Can with Stand Extremely High Temperatures. Formulated For Repairing Chimneys, Fireplaces and Sealing Wood-Burning Stoves and Appliances, This Product Has Strong Adhesion and Sets To Become Rock Hard When Fired.

Boss® 139 Hi-Temp Mortar Cannot Be Used In Areas Where There Is Constant Movement, or Where Wet Conditions Exist or May Occur.

Boss® 139 Hi-Temp Mortar Has Been Tested and Exceeds Astm E-136. Can Be Used In Wood Frame Construction Where An Astm E-136 Non Combustible Sealant Is Specified and Where Allowed By The Building Code. This Includes Sealing Around Pipes, Ducts, Vents and Chimneys At Ceiling and Floor Level Before Drywall Is Applied.


  • Can with Stand Extremely High Heat
  • Apply Using A Standard Caulking Gun
  • Dries Rock Hard When Cured and Fired
  • Safe To Use and Handle
  • No Harmful Odors
  • Water Clean-Up (Prior To Curing)
  • Voc Compliant
  • Contains No Asbestos Fillers Of Any Kind
  • Meets Residential Construction Code Approvals Including I.R.C.

California residents: see Proposition 65 Warning

Weight1.5 Pounds (Lb)
Width2 Inches (In)
Height8.25 Inches (In)
Country of OriginUSA
Length2 Inches (In)
UV ResistantNo
Includes4 Inch Nozzle
ApplicationHi-Temp Non-Combustible Mortar For Repairing Chimneys, Fireplaces, And Sealing Wood Burning Stoves And Appliances.
Comments/NotesCan Contribute Credits
CompositionSilicate Cement
FunctionsFire Block, Draft Stop, Sealing
Size10.1 Ounce
StandardsASTM E-136, IBC/IRC, BOCA National building Code, CABO one and two family dwelling code, UBC Section 796, BOCA-SBCCI-ICBO-NFPA Building Codes
Temperature Range0°F to 800°F (-17.7°C to 426.6°C)
TypeFire Block
UL ListedNo
UL RecognizedNo