Method one: sealing the stack nozzle to cool. And it will take about 16 hours to cool . Cooling by this way, the gloss of finished charcoal will be much more better. 
Method two: open the stack nozzle completely to cool.  Cooling by this way, there will no gloss of the finished charcoal. It will take about 16 hours to cool. 
Above that two cooling method, it is the ideal time to take out the charcoal when the temperature in the pot is about 40centigrade.

Remarks: if there is no Temperature Measuring Equipment, or the Temperature Measuring Equipment was broken, heating the stove with Medium Fire for 7-8 hours to carbonize. During the whole firing procedure, bit fire is firbided strictly. At the end stage of carbonization，when the smoke had reduced obviously, and its colors become light, then turn off the fire , seal the fire. Carbonization is finished