C-l JOURNAL OF FORESTRY 



'llic Kiln Drying of Jarrah. By C. E- Lane-Poole, Conservator of 

 Forests. Western Australia. Bulletin No. ], Forests Department of 

 Western Australia. 1919. Pp. 28. 



Tarrah. a s])ecies of eucalyptus, is one of the leading timbers of 

 Western Australia. It is used not only for rough construction of all 

 sorts, but also for high-class work, such as furniture and cabinets, 

 i leretoforc jarrah lumber was air dried only, with the result that the 

 timber de])reciated considerably, and often was not sufficiently dry when 

 remanufactured. In fact, much stock thicker than one inch is imported 

 because native woods are not properly seasoned. The increased demand 

 for luml)er, and the increased cost of long-time air drying, together with 

 its deficiencies, prompted the Forests Department to experiment in 

 the kiln drying jarrah. 



Three Tiemann water-spray kilns are being used for the experiments. 

 (Jne of these kilns, of experimental size, was first erected at a com- 

 mercial plant, and later two other somewhat larger kilns were built on 

 the grounds of the University of Western Australia at Perth. These 

 kilns are of typical design, except that in one the spray water is heated 

 by passing it through a steam jacket instead of in a well and that con- 

 densing coils are not shown in the ilustrations or mentioned in the 

 text. The inclined method of piling was used, a space being left 

 between the edges of the boards. 



Green one-inch jarrah, with a mcjisture content of o.") to 86 per 

 cent was satisfactorily dried to ^'i per cent moisture in twenty days. 

 Apparently this was as low a moisture content as was desired, although 

 the i)urpose for which the lumber was to be used is not given. 



Sample pieces were weighed from time to time to determine the rate 

 of drying and disks were cut every few days to test for case hardening. 

 At the end of the run the lumber was steamed to remove any set in the 

 surface layers. By using ''safe'' temperatures and humidities no par- 

 ticular difficulties seem to have been encountered. The author recom- 

 mends a temperature of lOo degrees F. and a humidity of 86 per cent 

 to begin with. The temperature is then gradually raised wnthin the 

 piles but the baffle plate temperature is kept constant so as to simplify 

 the operation. No ill effects resulted in using temperatures up to 

 loO degrees F., but at higher temperatures jarrah is very subject to 

 severe end checking and, still worse, collapse. A psychrometric chart,, 

 working somewhat on the principle of a slide rule, is included in the 

 bulletin. By placing a straight-edge so that it coincides with the dry- 

 bulb temperature and with the baffle plate, or saturation temperature. 



