How to make high temperature ceramic refractory cement hearths!

Prototype Gasifier Build

How to make your own high temperature refractory cement!

Today, i'd like to talk about high temperature refractory cement.  What is refractory cement? well its basically a cement that is composed of some sort of high temperature ceramic or clay.  

This special type of cement is used to make molds for metal pouring castings, kiln, forges, and gasifier hearths! 

Yup, you heard me right I am going to mix up my own high temperature ceramic cement for the inner hearth piece of the gasifier.  

Wood Gasifier Inner Hearth

The inner hearth needs to be made out of some sort of high temperature material since the inner gasifier zone can reach 1200 – 1500 deg. F .  At these high temperatures most carbon and stainless steels oxidize very quickly.  Basically the metal will rust very quickly and become too weak to hold the heavy fuel in the hopper.


I decided to make my own refractory because I have been having a very hard time located a local source for refractory cement.  I located a website called  where this metal smith explains how to make your own forges, and kilns.  I am going to use this same recipe to create my own cast-able refractory cement.

The basic recipe is:

The refractory mix is composed of Portland cement (1.5 parts), silica sand (2 parts), perlite (1.5 parts) and fireclay (2 parts). The first three components are mixed together thoroughly.- BACKYARDMETALCASTING.COM

I have already located a local supplier for the fire clay, silica, and portland cement.

Prices where as follows:

50lbs bad of fire clay is $22.00 

50lbs bag of silica is $22.00

94lbs bag of portland cement was $8.00

and 10- 20 bucks for the perlite 

so I can make about 150lbs of refractory for less then $60;  this should be plenty of material for a few trial casting and for the hearth its self.  I have ordred the fireclay and the silica from a local clay studio.  Once I pickup my order I will begin building a trial mold for a test pour!

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12 comments… add one
  • dvdimitrov

    Hi John,
    Please give accurate dimensions so as to make proper form for casting.

    • Jfedock

      Not sure what you mean by proper for the form? I am making a inner hearth the same size as Larry specified. You can find by clicking the link. Just build the form as close as you can .. it doesn’t need to be perfect .

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  • anthony

    Hey, I would like to know how this turned out for you. I am interested in building a rocket stove – forge and need cement that could withstand 2000 degrees, and 3000 would be better. Thanks!

    • Jfedock

      It didn’t work out too well .. The mixture was very brittle and ended up falling apart . I never fired it but the portland cement will certainly burn out.. You need to find a higher temp binder such as water glass (sodium silicate) or alumina. I ended up purchasing some castable refractory from Spar to build my oil fired foundry

  • Paul

    If you want something that is going to last at those temperatures, you will need to construct the areas exposed to those temps from a very high grade of stainless steel. 330 stainless will begin scaling at repeated use around 1700-2000 degrees. Even higher grades such as the 600 series (refered to as Inconell) would be best for anything over 2000. That or titanium.

  • Bill

    I’d be very suspicious of any refractory cement recipe that includes perlite. Perlite is used in planting soils because it absorbs moisture, and the last thing you want in high temperature cement is trapped moisture which will turn to high-pressure steam within your refractory cement. Try the Mizzou refractory casting cement that Harbison Walker sells for about $54 for a 55 lb bag. Normal refractory cement is meant for thinner usage, such as the 1/4″ mortar between firebricks, but refractory casting cement is designed to be used in thicker applications.

    • Jfedock

      You are correct . The mixture was a failure, just buy real refractory cement. It will work much better for you

  • MikeJ

    I think there’s some confusion between perlite and vermiculite. Perlite is lava glass, and when used in soil increases drainage, whereas vermiculite is used in soils for it’s ability to retain moisture. Many rocket stove enthusiasts use perlite when constructing their burn tunnels and heat risers because of its ability to insulate and retain the heat which improves combustion of the gases produced after ignition.

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