202 FARM FORESTRY 



The Dipping Method. In this method the creosote is 

 placed in a tank or barrel and the ends of the posts are dipped 

 in the creosote. This is a more effective method than the brush 

 method, but the creosote will not penetrate the wood very far. 

 Both ends of the posts are sometimes dipped and often the 

 tops of posts that have been treated by the open tank method 

 are treated by dipping. 



The Open Tank Method. In the open tank method the 

 posts are placed in a tank with creosote and heated to near 

 the boiling point for several hours and then allowed to cool 

 down in cold creosote. When the posts are heated in hot 

 creosote the air inside the posts expands and a large part of 

 the moisture in the wood is changed to steam and driven off. 

 There is an outward pressure set up in the posts. After the 

 posts have been heated for some time in hot creosote, if they 

 are immediately placed in cold creosote, or if left to cool 

 down in the creosote, the heated air inside the posts will con- 

 tract and the steam will change to water forming a partial 

 vacuum inside the wood. By atmospheric pressure the creo- 

 sote will be forced deeply into the wood to take the place of 

 the air and moisture forced out of the wood in heating. This 

 forms a shell of creosoted wood about the post, all cracks, 

 defects and season checks being rilled. In some kinds of woods 

 the creosote will sink an inch or more into the wood. 



Preparation of the Posts for Treatment. The posts should 

 be thoroughly seasoned or air dried before treatment, as the 

 presence of much moisture in the wood tends to prevent the 

 entrance of the creosote. The posts should be piled loosely 

 in some place out of the sun, but where the air will circulate 

 freely, for several months. If piled in the sun the posts are 

 apt to season check badly. The better the posts are seasoned 

 the easier will be the treatment and the deeper the penetra- 

 tion. All the bark should be removed, especially the papery 

 inner bark, as this prevents the creosote from entering the 

 wood. Usually only about 40 inches of the lower end of the 



