I am just adding some more info to roberts post on the casting failure. The clay we used was fire clay bought from a pottiers supply store. I beleive it had a cone 10 rating and was said to be good for 2500 degrees. The first mix we did nt use this fire clay and had the same results. The second mix was mostly fire clay (200lb dry) one bage +/- vermeculite and two pails of refractory cement. After 24hrs the casting was fired, the second day the casting was fire again. Sever cracking occured and when the sides were removed, the casting was cracked so bad that it will not hold together. I have watched a vid on youtube describing this method of casting twice and can not figure out what went wrong. Please help!
