180 



IMPREGNATION 



(d) A METHOD CALLED "SIDERIZINQ" injects by a boiling process a solution of copperas (sulphate of 

 iron). The wood thus treated is dried, and liquid glass (a hot solution of silicate of alumina) is applied 

 to its surface. By a chemical reaction, silicates of iron are formed in the outer layers, which are insoluble 

 in water and resist decomposition. The wood, at the same time, obtains a beautiful gloss. 



III. Use of hydrostatic pressure. A solution of copper (blue vitriol) is used after Boucherie. It is 

 kept in a tank 30 to 40 feet above ground. The timber, fresh cut with the bark on, is yarded on a rough 

 log-deck underneath the tank within 10 days after felling. At the big end of each log a ring made of 

 rope is held in place by a heading nailed or screwed to it. A hose connected with the tank by a system 

 of pipes injects the liquid into the small cavity formed between log and heading. After a few days, drops 

 of blue vitriol solution appear at the small end, indicating that the process is completed. The pressure 

 being slight, only the outer sappy layers are impregnated. This method is largely applied in France, often 

 in the woods themselves, to telegraph poles of spruce or fir. Expense, per cubic foot, 4 cents. Telephone 

 poles treated after this method will not do in soil containing lime, for the reason that blue vitriol is leached 

 out readily by water rich in carbon dicxide. 



IV. Use of air pressure (open tank treatment). The open tank process is adapted to the impregnation 

 of fence posts in particular. The wood is first heated and then allowed to cool in the preservative. When 

 heated in the preservative, air and water are driven from the wood cells 

 and from the intercellular spaces of the wood. When cooling, the liquid 

 preservative enters into the spaces previously occupied by air and water, 

 owing to the pressure of the atmosphere. 



The liquid usually used is creosote, costing in the East from 12 

 to 15 cents per gallon. 



(a) Single OPEN TANK TREATMENT. (After Farmers' Bulletin No. 387):- 



1. Raise the temperature of the creosote to 220 degrees. 



2. Put posts in tank, submerging them 6 inches deeper than 

 the ground line, to which the posts will be imbedded in the 

 soil afterward. 



3. Maintain temperature at 220 degrees for six hours. 



4. Allow liquid, with the posts standing in it, to cool down for 

 12 hours. 



(b) Double OPEN TANK TREATMENT: — 



1 . Have one tank filled with 

 creosote heated to 220 

 degrees, and another 

 heated to 120 degrees. 



2. Submerge posts from 

 one to three hours in the 

 hotter bath 6 inches deep- 

 er than the ground line, 

 maintaining temperature 

 at 220 degrees all the 

 time. 



Open tank treatment of fence posts. (Photo picture from a Forest Service bulletin.) 



3. Transfer the posts as 

 quickly as possible from 

 the hotter to the cooler bath, and let them remain in the latter from 30 to 120 minutes. 



By this simple method, du-able fence posts may be obtained cheaply from beech, maple, boxelder, &c. 



What, indeed, is the use of raising catalpa posts on valuable praerie soil, when posts of equal durability 



and of equal strength can be obtained cheaply and at once by the proper impregnation of ordinary woods' offall? 



