The Durability and Preservation of Woods 247 



out that rots a wood most quickly. This coating should 

 be of an oily or resinous substance which will make' a 

 smooth coating and will not peel off when dry. It should 

 be applied to the whole exposed surface. 



Coal tar 



Coal tar is probably the best of these coverings. If 

 applied hot and mixed with oil of turpentine, deeper pene- 

 tration and hence better protection is secured. One part 

 of unsalted grease to three parts of tar oil answers the same 

 purpose as the turpentine and is cheaper. One barrel of 

 coal tar will cover from two to three hundred posts if 

 properly applied. 



Oil paint 



Oil paints may also be used to advantage on well- 

 seasoned wood. They are made of boiled linseed oil 

 mixed with lead, pulverized charcoal or some other sub- 

 stance to give it body. Soaking the dry wood in crude 

 petroleum or creosote is also recommended. 



Lime white-wash 



Plain lime white-wash makes a fairly good protective 

 covering. It is not, however, as good as an oily or resinous 

 substance because the salts leach out of the wood rather 

 easily. As long as the lime is present, it works perfectly, 

 but the lime washes out. The wood must, of course, be dry 

 and the white-wash spread evenly. If shingles are to be 

 treated in this way, they should be dipped before being 

 laid. 



