76 Preservation of Timber 



are that it is essentially antiseptic, it does not corrode iron, and 

 it is easily applied ; on the other hand, it is rather expensive 

 and it is inflammable. 



The heart- wood of larch, oak, etc., cannot be successfully treated, 

 but these are sufficiently durable untreated. Thinnings of Scotch 

 pine for temporary fencing, deal of all kinds, gates, gate-posts and all 

 fencing, are rendered more durable by creosoting. 



The durability of the timber treated will depend, however, on 

 the quality of the material used and the method of application. 



There are three methods in use : 



(1) Impregnation under pressure. 



(2) Simple immersion in cold creosote. 



(3) Simple immersion in hot creosote. 



The first method requires such special apparatus as to make it 

 available only for treatment of large quantities of wood. It is 

 quicker, and more thorough, however, than the others. 



The second method is of no great value, where permanency is 

 required, though timber so treated is more durable than when 

 untreated. 



The third method is the best for general estate purposes, 

 although it is slower than the first. A suitable plant is illustrated 

 in the diagram. The timber to be treated is placed in the steeping 

 tank ; sufficient creosote is pumped up from the storage tank ; and 

 the fire underneath is lighted. 



The temperature is an important consideration, as if heated 

 above 200 F. there is a great waste of creosote. It is advisable, 

 also, to have a lid to the steeping tank, even if only loosely fitted, 

 to prevent loss of creosote. 



Messrs. Black advise that the creosote should be kept hot during 

 the day and allowed to cool during the night. Two or three days is 



