Timbers. 



218 



[March. 1912. 



much more rapidly than that cut in 

 autumn or winter. Soaking the timber 

 in water, the degree of exposure to 

 the air, and the method of piling the 

 timber also affect the rate of season- 

 ing. Timber which is seasoned rapidly 

 is much more liable to split than that 

 which is seasoned more slowly. In the 

 latter case numerous small splits are 

 formed, but these close again when the 

 wood absorbs moisture, and apparently 

 no detrimental effect is caused. If, how- 

 ever, the wood seasons rapidly, wide 

 and deep splits may be formed, which 

 do not again close, and which not only 

 decrease the strength of the timber, but 

 materially hasten decay by allowing 

 entrance of insects and fungi. 



Application of Preservative with a 

 Brush. — A very simple method of using 

 a preservative is to apply it to the sur- 

 face of the wood with a brush, but 

 while experiments carried out in this 

 direction by the Forest Service have 

 given good results, this form of treat- 

 ment does not present a complete solu- 

 tion to the question of timber preserv- 

 ation. It is especially useful, however, 

 where the erection of even the simplest 

 plant would not be justified, as the 

 cost is very low. Creosote was applied 

 hot to poles of chestnut, cedar and pine, 

 and the average amount of preservative 

 absorbed in each case is shown in the 

 following table :— 



Species. 



Chestnut... 



White cedar (Southern U. S.) 



(Northern U. S.) 

 Red „ (Western U. S.) 

 Yellow pine ( ) 



Absorption per Pole, 



Length and 

 Diameter of 

 Pole. 



Length 

 Treated, 



1 coat 



2 coats 



lb. 



lb. 



ft. in. 



ft. 



26 



4-7 



30 x 7 



6* 





4-9 



30 x 7 



6* 



30 



4-4 



30 x 7 



6* 





6-5 



40 x 8 



8+ 



2-4 



3-6 



40 x 8 



7t 



Between 2 ft. and 8 feet from butt end. t-From butt end to height indicated. 



In these experiments a penetration of 

 from & in. to j in, was obtained in sea- 

 soned timber. With regard to chestnut, 

 it is stated that in some cases failure of 

 treatment was due to the tendency of 

 the thin sapwood to scale off after ex- 

 posure to weather and that better re- 

 sults might have been secured if the sap- 

 wood had been shaved off for a few feet 

 above and below the ground-line, so that 

 the preservative would be applied to the 

 more firm hearcwood. Applications of 

 carbolineum, creolin and tar were also 

 made with a brush, the absorption of 

 tar by 6 ft, of pole being on an average 

 about 7 lb. Care should be taken in this 

 method to fill all splits formed during 

 seasoning ; the preservative should not 

 be applied when the surface of the wood 

 is wet or when very cold. In most cases 

 better results will be obtained by heat- 

 ing the preservative before applying. 



Treatment by Immersion. — Immersion 

 in a tank filled with preservative has the 

 advantage, in common with the brush 

 method of application, that the butt end 

 only of poles can be treated, and the 

 expense is avoided of applying the pre- 

 servative to the portion above ground, 

 which in many cases is sufficiently 

 durable without treatment. The treat- 

 ment consists in subjecting the timber 

 to successive baths of hot and cold pre- 

 servatives, these latter being thus 

 driven into the wood by atmospheric 

 pressure. Three methods of procedure 

 are possible :— (1) After the timber has 



been held in the hot preservative for the 

 required length of time, the heating 

 may cease and without change the 

 whole be allowed to cool ; (2) the timber 

 may be transferred from the hot liquid to 

 another tank of cooler preservative ; and 

 (3) the preservative may be changed, the 

 hot being drawn off and colder preser- 

 vative run into the treating tank. The 

 hot bath, as a rule, simply prepares the 

 wood for treatment, absorption taking 

 place, except in the case of very dry and 

 porous woods, during cooling. 



The length of time during which the 

 wood must be kept under treatment is 

 dependent among other things on the 

 species and condition of the wood. Thus 

 where the sapwood is narrow and the 

 heartwood difficult of penetration, the 

 treatment should be discontinued after 

 the sapwood has been impregnated ; and 

 where the sapwood is wide, the period 

 of treatment must be arranged so as to 

 avoid an unnecessarily large absorption 

 of preservative. 



In the case of porous woods a relative- 

 ly deep penetration is obtained as com- 

 pared with the quantity of preservative 

 absorbed by shortening the cold bath 

 and removing the wood while the preser- 

 vative is still fairly hot. Immersion of 

 chestnut in creosote at a temperature of 

 231° F. for four hours, gave relatively 

 good results ; while in the case of white 

 cedar (Northern U.S.), little advantage 

 was gained by prolonging the hot bath 



