1) Reduce the time at the temperature. If the recommended schedule has the process work being done at 780°C for 15 minutes and the glass is too rounded or more like a contour fuse, you can reduce the soak time to 5 minutes, depending on how over-done the pieces are.2) If the reduction in soak at process temperature does not work, then you can begin to reduce the process temperature. Often only 5°C with a 10-minute soak is enough. For some kilns it may be as much as 20°C again with a 10-minute soak.
Annealing Temperatures in a Cool Kiln
Exactly the same reasoning process is applied to both hot and cool firing kilns. You do not need to alter the anneal soak, even though it means you will start the temperature equalisation at a slightly lower temperature than the published schedules. This is because you have to increase the top temperature to get the effect you want and so would also be annealing in a cooler kiln. Since you are measuring the air temperature, the glass temperature will be above the air temperature and will still be in the safe annealing range.