356 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



The soaked wood was kept immersed six months, each piece having its check pieces from the same scantling, 

 which were not suhject to the same process, but were tested— one green and one dry. All soaked pieces were 

 seasoned in dry kiln before testing. All values were reduced to 15 per cent moisture. 



Lobolly pine. 



Soaked 6 months, and then dried 



Not soa,ked (mean oi green and dry teats) 



Bending 

 strength. 



Lbs. per sq. in. 

 10, 820 

 10, 570 



Compression 

 strength. 



Lbs. per sq. in. 

 6,780 

 7,060 



BBFECT OF "BOXING" OR "BLEEDING." 



"'Bleeding" pine trees for their resin — to which only the longleaf and Cuban pine are subjected — has generally 

 been regarded as injurious to the timber. Both durability and strength, it was claimed, were impaired by this 

 process, and in the specifications of many architects and large consumers, such as railway companies, "bled" timber 

 was excluded. Since the utilization of resin is one of the leading industries of the South, and since the process 

 affects several millions of dollars' worth of timber every year, a special investigation involving mechanical tests, 

 physical and chemical analyses of the wood of bled and unbled trees from the same locality were carried out by this 

 division. The results prove concusively (1) that bled timber is as strong as unbled if of the same weight; (2) that 

 the weight and shrinkage of the wood is not affected by bleeding ; (3) that bled trees contain practically neither 

 more nor less resin than unbled trees, the loss of resin referring only to the sapwood, and, therefore, the durability 

 is not affected by the bleeding process. 



The following tattle shows the remarkable numerical similarity between the average results for three groups 

 of trees, the higher values of the unbled material being readily explained by the difference in weight: 



Longleaf pine. 



Number of 



tests. 



Specific 



weight of 



test pieces. 



Bending 

 strength. 



Compression 

 strength. 



Boxed and recently abandoned 



400 

 390 

 535 



0.74 

 0.79 

 0.76 



Lbs. per sq. in. 

 12, 358 

 12, 961 

 12, 586 



Lbs. per sq. in. 

 7,166 

 7,813 

 7,575 



Boxed and abandoned 5 years 





The amount of resin in the wood varies greatly, and trees growing side by side differ withixi very wide limits. 

 Sapwood contains but little resin (1 to 4 per cent), even in those trees in which the heartwood contains abundance. 

 In the heartwood the resin forms from 5 to 24 per cent of the dry weight (of which about one-sixth is turpentine and 

 can not be removed by bleeding), so that its quantity remains unaffected by the process. Bled timber, then, is as 

 useful for all purposes as unbled. 



To give an idea how necessary it is that a large series of material be tested before making 

 statements of the strength of wood of any species, we reproduce one of the many tables contained 

 in Bulletin 8, which at the same time exhibits the variation of strength throughout the tree and 

 from tree to tree. 



