Gold hold - should we then reduce our top fusing temperature?
I've found that when I include the "gold hold" on the way up to fusing temperature, my glass then over-fires. causing dog-boning at what should be a tack fuse.
I was making a series of large panels, 30 x 60cm incorporating violet and gold purple; thicknesses varied from 4 to 7mm thick, so I annealed for a thickness of 14mm.
Given that my kiln is around 10 years old & fires hotter than the read-out on the controller, I normally tack fuse at what my kiln thinks is 720° centigrade. My kiln schedule (in centigrade) was thus:-
222°C / hr to 627°C; 30 minute bubble squeeze.
222°C / hr to 663°C; 2 hour hold to strike the gold bearing glass.
333°C / hr to 720°C - tack fuse temperature in my kiln - 10 minute hold.
As fast as possible / "full" down to 482°C. 2 hours 30 minutes anneal hold, then
40°C / hr to 427°C, then
72°C / hr to 371°C, then
240°C / hr to 25°C. End.
Without the 2 hour hold at 663°C, this would have given me a good tack fuse. My question is, if the extra heatwork involved in striking the gold-bearing glass causes the glass to fuse at a lower temperature, how much should I drop my top temperature by? If I want an intermediate fuse, I'd normally go up to 750°C, or I full fuse at what my kiln thinks is 780°C, so should I be dropping my top temperature by 40°C or so?