2 14 CARBONIZING IN ORDINAKY KILNS. 



dies of dry grass should be kept handy, in order to get up plenty 

 of light in case of accidents. 



When, with the gradual downward progress of the carbonization, 

 clear blue flames issue from the base of the kiln, the work is com- 

 plete and the fire must be caused to die out without delay. This 

 is .done by shovelling on fresh earth and moistening the covering 

 until smoke ceases to come out. A little superficial smoking, due 

 to the conversion of the moisture in the covering into steam, must 

 not be mistaken for real smoke. It is especially along the base of 

 the kiln that draughts are likely to continue to enter, and it is 

 here that the covering should receive extra strengthening. 



8. — Opening of the kiln. 



Even after the fire has gone out, the temperature inside the kiln 

 will still be high enough to cause the charcoal to light up again, if 

 air were admitted. On this account the kiln must -be allowed to 

 cool down sufficiently before it is opened. If we waited until the 

 contents were cool enough to be comfortably handled, a week or 

 even a whole fortnight might elapse. In practice, therefore, the 

 work of taking out the charcoal may be commenced, according to 

 the size of the kiln and the skill of the burners, from 1 to 3 days 

 after the carbonization has been completed. 



To prevent the charcoal from burning it should be taken out only 

 at night, when the air is cool and damp and burning pieces can be 

 at once detected by their glow and put out. The simplest plan to 

 follow is to cut open a section of the kiln on one side, pull down 

 quickly as much charcoal as possible, and cover up the kiln with- 

 out delay. When so much charcoal has been picked out, another 

 section adjoining the first should be pulled down, and so on until a 

 complete circuit of the kiln has been made. If the remaining 

 charcoal is also cool enough, a second and even more such tours of 

 the kiln may be made. A small kiln may be emptied out in a 

 single night ; but usually the work requires at least two nights, as 

 the charcoal in the centre is always hot enough to take fire readi- 

 ly, and covering it up for another night brings about the necessary 

 reduction of temperature, The emptying of a large kiln may 

 take several successive nights. 



As the charcoal is picked out, it should be spread out on the 

 ground, otherwise a single piece taking fire would set the whole 

 heap burning. When spread out thus, individual pieces becom- 

 ing aglow are detected at once and put out with a few drops of 

 water. 



