In my kilns, 1275 would be
In my kilns, 1275 would be too hot. Try 1225-1250, and *watch* the process as the temp nears 1200. With things like drop molds, you can’t just set a schedule and walk away — you have to observe when you get close to the processing temp and then kick the kiln into its annealing schedule when the glass is where you want it to be.
Additionally, 900 is really too low (IMO) for a temp to “even out” the heat in the glass. I typically do 30 minutes at 1100. At that point, you may already begin to see movement in the glass.
Jester’s Baubles Fused Glass Designs