low fire clay molds
Your firing schedule is excessively conservative. I have made many molds from low fire clay and my schedule regardless of thickness follows….
Dry 1-2 weeks with plastic over (prevents cracking)
Dry on top of kiln overnight (during the firing of other items)
To cure or complete the mold my kiln firing is………
300 -1000 hold 30min
500-1500 hold 5min
off (let cool basically overnight)
then wash with kiln wash like any other mold.
Never had a problem and still use every mold I have made.