Found these and have no idea if practical or not so any input is welcome, even a homemade version of stuff like ITC-100 if it exists would be handy. Refractory Cement Recipe #1 What You Will Need: Portland cement (You can purchase a 94 lb. bag at your local hardware store for less than $10.) 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 averages less than $10.) The Formula 1.5 parts Portland cement + 2 parts Perlite + 2 parts silica sand + 2 parts fire clay What to Do: Using the portions listed measurements listed above, mix the Portland cement, Perlite, and silica sand together thoroughly. Combine the mixture with 2 parts fire clay. 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 do sell it in ½ gallon buckets for $12 to $20.) What You Will Need: Furnace cement Perlite Water 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 Perlite for each part of Furnace cement, the results will be weak. However, if you use less than 4 parts Perlite for each part of Furnace cement, it will take forever for it to seal. When the Furnace cement and Perlite are combined, you will get a consistency that is very sticky 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. Form your preferred shape and allow 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.) Formula 4 parts Perlite + 1 part fire cement What to Do: Mix Perlite and Fire cement using the above measurements. Allow it to try for several days at room temperature. (68⁰F -72⁰F) Bake at 250⁰F for several hours until no steam or smoke is coming out of it. Allow it to cool completely. Repeat at a slightly higher temperature. Repeat this step until it is completely baked in. Helpful Tips Regardless of what recipe you use, be sure to follow it just right. If the slightest little thing is done wrong, you could end up with cement that completely crumbles when its fired up to its full temperature. When purchasing Perlite, make certain 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 a 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 in order to make this process faster and easier. However, you can no longer use these things once water has been added because the mix will be too gooey and thick. When adding water, add as little as possible. Safety Information Under NO circumstances should you try to fire up your furnace to a high heat UNTIL you are absolutely certain it is COMPLETELY DRY. There is a possibility that it could explode. It will take SEVERAL days to dry, especially if it is a bigger furnace or fireplace. Do not try to speed up the process. Be patient!