Ayelet's refractory

 
Which I showed you after its first test firing in the last salt kiln,when it looked fine and promising as a home-made alternative to ready-mix refractory.On a whim I stuck it back for another round with the salt,and now it doesn't look so happy,having taken on a green,glassy layer of salt-glaze.Mind you,Alon's sample pieces,made up from various recipes,and intended for casting his kiln at Tel Hai,all came out of this firing with vitrified surfaces too.The bought castable,from which the salt kiln is constructed,looks fine after about 10 firings [5 at its original site in my garden,5 at Sydney's].Possible conclusion:cast the kiln with an inner skin of the tougher commercial mix,back it up with a thickness of home-made.