Hmm- my propane forge has a liner made of portland cement, clay dirt from the yard, silica sand, and perlite. The proportions were about 1:1:1:5, if I recall correctly. I use a layer of half inch kaowool inside a two inch layer of the above refractory, and have never had problems in many hours of operation. I've used portland cement in every homemade refractory I've ever made, and if you keep it under about 10% be volume, it seems to have few problems. |