Red Pottery Clay With Sand for High Temp Mortar?

Will this work? It's winter and kind of hard to dig up clay. I have some red clay i had gotten for pottery. It seems i could just use that with sand for my hight temp mortar around the combustion unit.

John Palombo wrote:Will this work? It's winter and kind of hard to dig up clay. I have some red clay i had gotten for pottery. It seems i could just use that with sand for my hight temp mortar around the combustion unit.

Red clay is not the best choice since it is full of iron oxide and has very little silica. The high temps in the combustion chamber will 'reduce' the mortar right out of the joints.

Even if it is combined with a lot of screened sand?

As a potter I would think that the high temps would vitrify your red clay but shrinkage might be a problem making the clay fall out of the joints. The addition of sand or grog would lessen the chances of shrinkage. Having very close fitting joints would also be highly desirable. I would use potter's clay with heavy grog such as clean sand. Some clays might melt at temps higher than 2100 F. Use a high fire clay.