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Refractory Skulls

Refractory Cement Casting- Its Hot Stuff

What is Refractory cement?

Also known as Cast-able Refractory or Fireplace Cement, is a high-heat tolerant refractory material designed for cast-able refractory cement pizza ovens, fire pits, and backyard forges. Refractory cement can withstand temperatures above 2500°. 

Further, refractory cement is a hard, heat-resistant material used in high-temperature applications. They are created by mixing different types of raw materials like clay, sand, and lime with Portland cement, making a brick-like structure that is strong enough to withstand heat. These materials are typically used to patch furnaces or bond bricks together because they can resist the intense heat generated from these furnaces for extended periods.

Refractory cement is used to patch or line furnaces and bond bricks or joints in high-temperature applications. These raw materials are hard and heat resistant, protecting the furnace from damage. In addition, they contain different materials such as clinker, slag, dolomite, and other minerals. Grab a silicone or ABS mold and get to casting for a fire resistant ornament.

Where Can I Get Refractory Cement?


Refractory Cement 

  • Always follow the instructions. If the simplest step is missed or is done wrong, you could end up with cement that completely crumbles when it is fired up to its maximum temperature.
  • When purchasing Perlite, make sure to choose a pure form. Do not purchase Vermiculite or a blend of several ingredients meant for plants.
  • Be aware that Portland sand is not a ready-made mix. It is pure cement that does not contain sand or rocks.
  • If you are building a forge, do not use a recipe that calls for Portland sand. It tends to turn to dust and crumble away quickly.
  • Be aware that it can take quite some time for the fire clay to bond to the silica sand when mixing the dry ingredients together. If you have a vibrating tumbler, cement mixer, or rolling tumbler available, you may want to use it to make this process faster and easier. However, you can no longer use these things once the water has been added because the mix will be too gooey and thick.
  • When adding water, add as little as possible.

How To Make Refractory Cement

Refractory Cement Recipe #1

What You Will Need:

  • Portland cement (You can purchase a 94 lb. bag at your local hardware store )
  • Perlite (Can be purchased for $10 to $25.)
  • Silica Sand (A 50 lb. bag costs less than $25.)
  • Fire clay or Well drillers mud (A 50 lb. bag.)

The Formula

1.5 parts Portland cement + 2 parts Perlite + 2 parts silica sand + 2 parts fire clay

What to Do:

  1. Mix the Portland cement, Perlite, and silica sand together thoroughly using the portions listed above. Next, combine the mixture with 2 parts of fire clay.
  2. Once the mix has the consistency of stiff cookie dough, pack it into the performed form. You may need to add a little bit of water to get the right consistency. Allow it to dry for several days.


Refractory Cement Recipe #2

This recipe is an excellent option if you can find ready-made furnace cement. (Many home improvement stores sell it in ½ gallon buckets for $12 to $20.)

What You Will Need:

  • Furnace cement
  • Perlite
  • Water

The Formula 

1 part Furnace cement + 4 parts Perlite (This is by volume. For example, if you use ½ gallon of Furnace cement, you will need to purchase 2 gallons of Perlite.)

What to Do:

  1. Mix the ingredients together thoroughly using the above measurements. Be sure to stick to the formula. If you use more than 4 parts of Perlite for each part of Furnace cement, the results will be weak. However, if you use less than 4 parts of Perlite for each part of Furnace cement, it will take forever for it to seal.
  2. When the Furnace cement and Perlite are combined, you will get a very sticky consistency, to say the least. If you add around 2 cups of water per gallon of cement, it will be much easier to work with because it will have a consistency comparable to thin plaster.
  3. Form your preferred shape and allow it to completely dry.

Refractory Cement Recipe #3

Note: This recipe is for absolute bare-bones refractory cement.

What You Need:

  • Pure Perlite Standard 2.0-5.0 mm
  • Fire cement rated a minimum of 1400⁰F or higher. (Make sure it is at least 1800⁰F for brass.)


4 parts Perlite + 1 part fire cement

What To Do:

  1. Mix Perlite and Fire cement using the above measurements.
  2. Allow it to try for several days at room temperature. (68⁰F -72⁰F)
  3. Bake at 250⁰F for several hours until no steam or smoke comes out of it. Allow it to cool completely.
  4. Repeat at a slightly higher temperature. Repeat this step until it is completely baked in.

Comments 3

Alita on

When you say “fire clay,” do you mean kaolin or calcined (pre fired) kaolin? The recipe I use on my kiln shelves is a 50/50 mix of kaolin and calcined kaolin to keep shrinkage cracking to a minimum. I’m wanting to get a white (or add some vanadium for cream) color rather than the gray that the prepackaged refractory cement comes.

Adnan Arif on

Good .
Its working ..
But mortor colour is black…

Dan on

Any thoughts on substituting Hemp Hurd for the perlite in the “recipe”?

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