I am having difficulty understanding why the firing schedule for box casting (as listed on the video tutorials) and the firing schedule for open faced casting (as listed on the video tutorial) are so radically different?
I am doing an open faced mould (silica/plaster) using bullseye billet. The negative space of the mould is 6" x 11" x 0.75" (with this last dimension being somewhat varied through out the work). Initially I copied the firing schedule for box casting as the annealing stages coincidentally matched up with my work. This is the schedule:
1. Rate-100, Temp-200, Hold-6:00
2. Rate-100, Temp-1250, Hold 2:00
3. Rate-600, Temp-1525, Hold-1:00
4. Rate-9999(AFAP), Temp 900, Hold-6:00
5. Rate-12, Temp-800, Hold-0:00
6. Rate-22, Temp-700, Hold-0:00
7. Rate 72, Temp-70, Hold-0:00
BUT, the firing schedule for open faced casting is:
1. Rate-300, Temp-300, Hold-5:00
2. Rate-150, Temp-1250, Hold-5:40
3. Rate-150, Temp-1525, Hold-3:00
4. Rate-999(AFAP), Temp-900, Hold-4:00
5. Rate-27, Temp-800, Hold-0:00
6. Rate-49, Temp-700, Hold-0:00
7. Rate-162, Temp-70, Hold-0:00
Could you please explain the reasons for:
1)Holding at 200f vs 300f?
2)The different holding times at 900f?
3)The reason for holding at 1250f in the open firing schedule?
4)Why the annealing time in the box casting does not comply with your "annealing thick slabs" chart?
Thanks so much