Just finished laying the fire brick today and can’t wait to get morning on the next step. The directions mention that the shell coat can either be stucco or mortar. I have a good amount of high temp mortar mix left and was wondering if there is any reason I shouldn’t use it over the ceramic fiber blanket & chicken wire.
If your high-temperature mortar is made from our recommended blend of (4) materials (Silica / Pool Filter Sand, Fireclay, Portland Cement & Lime) - then you are fine.
But if your high-temperature mortar is from a refractory manufacturer (HeatStop 50, Mortar Mix 413, Sairset or Sairbond)… then NO. These high-end refractories BEGIN curing when they hit 800°. Sure, the high-temp mortars in a bag / dry will get hard… they won’t reach their full strength until they are cured (again, starting at 800°).
Thinking about using wet / pre-mix mortar? EVEN WORSE! Those refractories will stay soft / puddy-like until fired… and the outside of your oven will look like a back-side of a Florida alligator once it’s dry.
Stucco is preferred…
Mortar is runner-up.
Thanks!! I actually was using Heat Stop because I had a hard time getting fire clay near me to make my own mix!! I’ll find stucco or use mortar if I can’t.