1912.] 



Preservation of Timber. 



853 



treatment must be arranged so as to avoid an unnecessarily 

 large absorption of preservative. 



In the case of porous woods a relatively deep penetration 

 is obtained as compared with the quantity of preservative 

 absorbed by shortening the cold bath and removing the wood 

 while the preservative is still fairly hot. Immersion of chest- 

 nut in creosote at a temperature of 23 1° F. for four hours, 

 and subsequently in cold creosote for two hours, gave rela- 

 tively good results ; while in the case of white cedar (Northern 

 U.S.), little advantage was gained by prolonging the hot 

 bath beyond three or four hours. Good results were obtained 

 by treating red cedar (Western U.S.) for two hours with hot 

 creosote and one hour with cold creosote, although in this 

 case longer treatments sometimes gave better results. 



As regards the condition of the wood, it was found that 

 the drier the wood the more readily it may be treated. The 

 absorption of preservative by green timber is small and 

 irregular, and the treatment of unseasoned timber is unsatis- 

 factory in addition, on account of the liability of such wood 

 to split in drying, and thus expose untreated ,wood to decay. 

 Where it is decided to treat wood not thoroughly seasoned, 

 the temperature of the hot bath of preservative should be 

 high, about 215 0 F. to 230 0 F. Experiments carried out by 

 the Forest Service on wood which had been soaked in water 

 before seasoning showed that the wood was not rendered any 

 more permeable to preservative by such treatment. 



The Forest Service found that the sapwood of nearly all 

 the common species of wood of the United States could be 

 successfully impregnated by the open-tank process; while, 

 on the other hand, the heartwood of many species could only 

 be successfully treated by artificial pressure. The absorption 

 of creosote by poles of various woods was found to be as 

 follows, 6 ft. of the butt end being treated in each case : — 1 



Species. 



Absorption 

 per Pole. 



Penetration. 





lb. 



in. 



Chestnut 



ii's 



0'3 



White Cedar (Northern U.S.) ... 



48-4 



o-5 



Red „ (Western U.S.) ... 



39*5 



o-8 



Yellow Pine ( ) ... 



81-4 





Lodgepole Pine 



34 "o 



I "O 



