How to Make Kiln Mortar

Kiln mortar is often used in brick ovens.

Kiln mortar is a binder and filler that has several names including refractory cement. There are numerous recipes for kiln mortar and there are a three things you should know before you mix up a batch. First, it comes ready made in small amounts that you can buy anywhere. Second, although it will withstand temperatures above 2000 degrees it will inevitably crack, not from heat but from the expansion and contraction of the bricks around it. So, finally, it should always be applied in very thin coats.

Things You'll Need

• Rubber gloves
• Dust mask
• Fireclay
• Grog (firesand)
• 5 gallon plastic bucket
• Sodium silicate solution (liquid glass)
• Water

Instructions

1. Put on rubber gloves and a dust mask. Add one gallon of dry fireclay and 1 gallon of grog (a kind of sand with a high concentration of aluminum oxide) to a 5 gallon plastic bucket. You can buy both ingredients from potter's supply stores.

2. Pour 1 cup of water over the dry ingredients, to minimize the dust and mix the ingredients with your hands.

3. Add water to the dry mix 1/2 cup at a time and mix the mortar until it has the consistency of cookie dough.

4. Add 1 tbsp. of sodium silicate solution (liquid glass) to the wet mortar mix and continue to mix all the ingredients with your hands for another five minutes.

References

• Rumford Fireplaces; Building A Masonry Firebox with Refractory Mortar; Bob Rucker and Jim Buckley, January 2006
• Traditional Oven; Refractory Mortar and Wood Fired Ovens
• Robert Compton Pottery; "Books on Kilns & Tips on Kiln Designs"; 2011
• Sheffield Pottery Inc.; Kiln Brick Repair Kit; 2004
• Orane Refractories Pvt. Ltd.; Orabond
• Dick Blick Art Materials; Amaco Kiln Cement; 2011