THE ARTIFICIAL SEASONING OF TIMBER 



By S. Fitzgerald 



A History of Timber Dryers 



Timber which is cut into planks, and then stacked in the open for a 

 period in such a manner that the air has free access to the surface, is 

 said to be naturally seasoned. By this process the timber takes from 

 six months to four years to dry, and during this period it experiences all 

 the variations of the climate : varying aeration according to the winds, 

 varying temperatures in the different seasons, and varying humidity 

 according to the amount of rain and mist. The actual evaporation of 

 moisture from the wood is effected by the operation of these chmatic 

 conditions, namely, aeration and heat, while the process is restrained and 

 over-drying and hardening of the surface prevented by the third factor, 

 namely, the humidity. With the operation of aeration and warmth alone 

 the timber would be dried, but spoilt. With warmth and humidity 

 without aeration the timber might be dried, but its value would be much 

 lessened by fungus and mould. 



The seasonal changes of the year bring into play all these conditions, 

 but not in combinations which can be controlled. If it were possible 

 to have continuous March winds, and then gradually supply August 

 heat restrained by November humidity and eliminate the diurnal 

 irregularity of night, timber would season much more rapidly. 



It is, therefore, the function of the process of artificial seasoning to 

 produce and maintain by mechanical means the best drjdng conditions 

 of aeration and temperature, combined with the restraining influence of 

 humidity. It will be well here to submit some definition of an artificial 

 seasoning process. Timber placed in a room where there is an air 

 circulation will not dry without the further condition of heat. If the 

 room is merely heated, the material will naturally dry, but will spUt and 

 warp. Thus a room heated and ventilated does not supply all that is 

 necessary for a proper process. Many such rooms exist and are wrongly 

 termed " dr^dng-kilns." These can be used for completing the seasoning 

 of boards that are already nearly dry, but they are entirely unsuitable 

 for the rapid seasoning of fresh timber. A proper artificial seasoning 

 process is one in which ventilation, heat and humidity operate in due 

 proportion under proper control. 



The idea of rapidly bringing timber into a usable condition b}' 

 mechanical means, apart from keeping it in a covered or warm place, is 



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