CHARCOAL-MAKING. 537 



vii. Mode of Conducting the 



The normal process of carbonisation just described cannot 

 be secured always uninterruptedly. The draught is some- 

 times greater in one particular direction and the kiln itself 

 is seldom uniformly built or covered ; it may therefore settle 

 down unsymmetrically or burn too quickly or too slowly. 

 Charcoal-burners should know how to secure the kiln against 

 these mishaps, and keep it burning in as normal a manner as 

 possible. 



This is effected by the following procedure : The fire should 

 be led gradually from the top of the kiln to its base, so that 

 the kiln may settle down symmetrically and without burning 

 the charcoal. The space left open at the base of the kiln, 

 that is subsequently closed, may be re-opened if more 

 draught is required, and holes made in the upper part of the 

 covering through which flames protrude, in order to regulate 

 the burning. On the second or third day after kindling, the 

 first holes are made through both coverings down to the wood 

 on the leeward side of the kiln. These are usually in two 

 rows, somewhat below the flame at the top of the kiln. At 

 first the smoke issuing from these holes contains steam, but 

 the nearer the combustion approaches the holes, the clearer, 

 more pungent and pyroligneous it becomes; when it finally 

 turns blue, it denotes that the charcoal is burning. Before 

 the smoke turns blue, therefore, the upper holes must be closed 

 with paste by means of a flat shovel, and a fresh row opened 

 below the lower row. If burning proceeds too rapidly on any 

 side of the kiln, all vent-holes must be stopped, the covering 

 thickened and water applied if necessary. 



By means of these simple arrangements, which require the 

 burners' close attention, the wood in the kiln is carbonised 

 gradually. When the carbonisation is nearly over, the fire is 

 at the base of the kiln; holes are then opened there through 

 which at length flames protrude, showing that the burning is 

 completed. The burners must be now on the watch to 

 extinguish the fire at the right moment, and by applying 

 fresh paste or watering the kiln prevent any cracking or 

 bursting of the covering. 



