DURABILITY OF WOOD. 235 



From twelve to eighteen months is generally sufficient 

 to cure wood for ordinary use, while for special work ten 

 or more years may occasionally be required. If green 

 or wet timber is closely piled in warm weather it is likely 

 to rot. The best method of curing timber without resort- 

 ing to the use of expensive apparatus is to work it up at 

 once and soak it in water for from one to three weeks, to 

 remove the sap from the outside of the wood. It will 

 then season more quickly and be more durable than 

 when dried without soaking. Sometimes it is absolutely 

 necessary to thus water season large timbers, as it is im- 

 possible to get the sap out of them by atmospheric sea- 

 soning. Large checks. or cracks in the ends of logs or 

 other timber of large dimension may be avoided or greatly 

 lessened by painting the ends with linseed oil mixed with 

 ground charcoal or other material, to give it consistency. 

 Covering with cloth or tarred paper also lessens checking. 



Good Coatings for Wood consist of oily or resinous 

 substances that are easily applied in a smooth coat and 

 dry readily, yet do not have a.ny tendency to crack or 

 peel off. They should be applied to the whole exposed 

 surface. 



Coal Tar is one of the best materials for covering wood 

 to incren,se its durability. It is best applied hot, espe- 

 cially if mixed with oil of turpentine, as it then penetrates 

 more deeply. A mixture of three parts coal tar and one 

 part unsalted grease, to prevent the tar from drying too 

 quickly so it may penetrate the wood better, is recom- 

 mended. One barrel of coal tar will cover from two to 

 three hundred posts if it is properly applied. 



Oil Paints are next in value. Boiled linseed oil is used 

 with lead, pulverized charcoal, or other similar material, 

 to give it substance. Soaking the dry wood in crude 

 petroleum is also recommended. 



Lime Whitewash is a good preventive of decay in 



