To control the cooling rate, program a segment to a lower target temperature than that of the preceding segment. Most controllers do not use minus numbers for cooling. Just enter a lower target temperature than that of the previous segment.
If you want controlled cooling down to room temperature, use a target temperature of around 100 degrees F. If you want to control cooling through the annealing range of glass, you might use a target temperature of 750 degrees F.
The kiln will cool down to the target temperature (i.e. 100 or 750 degrees F) at the rate you specify. Then the kiln will shut off.
Suppose you enter a cooling rate that is faster than the kiln is able to cool? Depending on the rate you enter, you may get an alarm message. The controller, of course, cannot speed cooling beyond the kiln's natural cooling rate.
Note how long it takes your kiln to cool down naturally after it shuts off. Divide the temperature the kiln cooled by the hours of cooling. That is the kiln's natural cooling rate. To avoid error messages, program a slow cooling segment at a slower rate than your kiln's natural cooling rate. If your kiln cools at 200 degrees per hour, the controlled cooling rate should be 200 degrees or less.
Some glass artists flash-cool the glass just after it fuses. They open the door a few inches to remove heat, then close it again. This takes the glass down rapidly through the devitrification range. To program a flash-cool, use a rate of 9999. This shuts off the heating elements during that segment, allowing the kiln to cool rapidly. Cooling slowly through the annealing range would require a separate segment.
Note: During fast cooling, do not open the door all the way. Do not force-cool the kiln with a fan.
Controlled cooling is available on most but not all digital controllers. (That feature, for instance, is not available on the DTC 100, Paragon's first controller. But it is available in the DTC 600, 800, 1000, Sentry 2.0, and Sentry Xpress series Ramp-Hold mode. The Sentry 2.0 also has Slow Cooling in Cone-Fire.)