Castable refractories are different than mortar products in that they are designed to be cast into special shapes. For example Insul Stick, a product made by the manufacturer of Heat Stop, is a castable restoration product that can be parged over firebrick in a smoke chamber or for exterior applications. It provides insulating value and strength, and can also be used to seal wall penetrations. It can be cast, parged, or troweled, and should be applied 1/4" to 1/2" thick. You will need 2.5 lbs. per square foot when applied 1/2" thick. Insul Stick is packaged in 5 and 20 lb. pails.
Insul Cast is another refractory castable product made by the manufacturer of Heat Stop. It is a backup insulating product that can be applied under the hearth, behind the firebox, or over the dome in a firepit or bake oven. It is an ideal product to use as an insulator for bread and pizza ovens, and should be applied with a minimum thickness of 2". You will need 6 lbs. per square foot when applied 2" thick.
Heat Cast 40 is a castable refractory dry mix product that can be used to cast special shapes in a heat chamber (e.g. bake ovens, fire pits, fire boxes). For example, it can be used instead of firebricks as a hearth in a heat chamber. You will need 20 lbs. of product per square foot when applied 2" thick (which is recommended). It comes in a 40 lb. bag.