[Clayart] castable burnout period
lee at spencerandtaylor.com
Sun Jul 30 14:12:14 EDT 2017
I have used castable made with high alumina cement (calcium aluminate) and once used Portland. The Portland melted at top temperature and had to be replaced. It sounds like you may not have used enough cement to make much difference, though. During the first firing of my current kiln (all arches are cast) I went really slow, holding temperatures as suggested by Warren Frederick (the king of castables in my opinion) on his website "artistpotters.com". The last kiln I built using castable had only the firebox cover cast. We preheated overnight and just went slow up to bisque temp and then "let it rip".. No explosions or cracks. I would not waste the time or the fuel expense for a shakedown firing. Just go slow (especially up to 200 F.). I'd suggest holding several hours at 200 and then holding for an hour or so at the chemical water stage (800-900?? or whatever that is).
Best of luck!
Buffalo Creek Pottery
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