How can you improve heat distribution of a three-zone kiln that fires cooler on the bottom?

This answer is for the Sentry 2.0 controller. Instructions may vary for other brands. The controller has three display lights. They each represent a zone inside the firing chamber. When a light blinks rapidly, that zone is not receiving enough heat to maintain even heat distribution. The kiln will continue to fire, though. Slowing down the firing will give the kiln more time to even out the heating. That should give the underfired zone enough time to catch up with the other two zones. If a section of the kiln heated unevenly and the lights did not blink during firing, adjust the thermocouples with Thermocouple Offset. In this case, since the kiln fired cooler on the bottom, adjust the bottom section to fire hotter and the top and middle sections to fire cooler.