168 



MANUFACTURE OF CHARCOAL IN CHARCOAL KILNS (PITS) 



Large charcoal pit in Austria, ready to receive the covering'. 



III. The kiln is lighted early in the morning on 

 a quiet clay. A cylindrical chimney is closed on top 

 from above as soon as the fire is well started in the cap. 



A lighting channel, in the case of a pyramidal 

 chimney, is similarly closed. 



IV. The regulation of the fire and of the draft 

 are the most important functions of the attendant 

 who guides the fire evenly and gradually from the 

 cap down to the bottom. 



The means of guidance are:- 



(a) To check draft, increased earth cover; 



(b) To increase draft, holes of about 1 inch 

 diameter punctured through the cover 

 with the paddle reversed. 



If the wind is strong, all holes are closed and 

 the earth cover is increased. 



Cracks forming in the cover must be closed 

 at once. 



In dry weather the kiln is continuously sprinkled. 



The kiln may explode if the cover is too heavy and the draft too strong. 



The color of the smoke escaping through the punctures indicates, by turning blue and transparent, 

 the completion of the charring process above the punctures. 



The old punctures are then closed, and another row of punctures is made about two feet below 

 the closed holes. 



V. Refilling is required where dells are forming irregularly, while the kiln gradually shrinks to one 

 half of its original volume. 



For refilling, the cover over the dell is quickly removed, all holes having been closed beforehand, 

 and the dell is rapidly filled with new wood. 



VI. When the bottom holes show the proper color of smoke, the charring process is completed. All 

 holes are then closed, and the kiln is allowed to cool. 



The duration of the charring process is from six days to four weeks, according to size of kiln. The 

 contents vary between four and sixty cords. 



VII. Beginning at the leeward side, the kiln is gradually uncovered. The crust of earth, cut into 

 fragments, is thrown on again. The earth, trickling down, quenches the fire. After another twelve to 

 twenty-four hours, preferably at night, the coal is taken out, in patches or pockets, slowly and carefully, 

 so as to prevent the flames from breaking out. Water must be ready at hand to quench incipient fires. 



(E) STATISTICAL NOTES. The loss of weight in the charring process is 75 per cent. The loss 

 of volume is 50 per cent. Two cords of hardwood yield one ton of charcoal. 



In America charcoal is sold by the bushel, a bushel weighing about 25 pounds. 

 The expense for labor incurred in erecting the kiln and in producing the coal is 60 cents per ton 

 of product. 



(F) APPENDIX. In Norway, Sweden, and Russia kilns of trapezoid form are built of peeled logs 

 18 to 30 feet long. The logs are lying horizontally in the heap which has the appearance of an American 

 "skidway." 



The lighting channel runs lengthwise on the ground. 



The covering (branches below, mud above) is pressed against the vertical walls of the heap by 

 slabs or by small horizontal poles held in place by pilings or by posts. 



The fire is conducted from the small towards the big end of the trapezoid. 



