706 WOOD-CAIIBONISATION. 



the covering into a firm condition. All vent-holes should be 

 stopped at least one hour before filling a hollow, for a 

 whole day afterwards the burning should be conducted without 

 any holes in the kiln. The hollow made by the combustion of 

 the chimney is tilled on the first evening of the burning and 

 must often be filled again on the second, third, fourth and 

 even on the fifth evening. This top-filling is often required 

 several times on the same day ; in large kilns, as many as 

 15 to 20 top- and side-fillings may be required during the 

 burning and several more whilst the kiln is cooling. 



It is evident that filling hollows in a kiln must waste charcoal, 

 as by opening the covering a draught is caused and the fire 

 unduly stimulated ; charcoal is thus burned owing to the flames 

 breaking out, and in pressing down the contents of the kiln some 

 of the charcoal is broken into small pieces. Filling cannot, 

 however, be dispensed with ; every endeavour should therefore 

 be made to prevent the sides of the kiln from collapsing, and to 

 reduce the number of indispensable fillings to a minimum. 



viii. W'dtcliiii'i and CooVukj doicn the Kiln. 



Every evening during the burning of the kiln, the burners 

 should adopt proper measures to secure regularity in the burning, 

 l^laces where the charcoal is already burnt should be beaten 

 down with the mallet, any fillings which may be required should 

 be effected, cracks which may have opened in the covering should 

 be carefully closed and all holes closed if the weather is stormy. 

 Frequent inspection of the kiln at night is necessary. 



Towards the completion of the carbonisation, when the kiln 

 has sunk considerably and the upper covering is very dry and 

 cracked, it should be well beaten down and covered with damp 

 earth, or watered, so as to exclude the air more and more. As 

 soon as the lower covering burns and flames appear at the 

 foot of the kiln, it is clear that the carbonisation is completed ; 

 all vent-holes must then be stopped and the whole surface of the 

 kiln covered with damp earth. The kiln is then left alone for 

 about 24 hours. Then in order to hasten the cooling, the 

 burners remove the covering in strips and apply fresh earth to 

 the glowing charcoal so as to fill up all crevices. This rapidly 

 extinguishes the fire, an important point when the weather is 



