TIMBER PHYSICS SOUTHERN PINE. 



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many, in part, unreasonable and contradictory claims about closing or opening of pores, chemical or physical 

 influence on the sap and its contents, albumen, gum, resin, sugar, etc., substances whose very existence in many 

 cases is problematical or doubtful, the general claims of increased checking and warping, " casehardening," 

 "honeycombing," etc., as well as reduction of strength, are still prevalent even among the very manufacturers 

 themselves. The manner and progress of the kiln-drying may render this otherwise useful method of seasoning 

 injurious. Rapid drying of the heavier hardwoods of complicated structure, especially in large sizes and from the 

 green state, is apt to produce inordinate checking and thus weakening of the material. For Southern pine, however, 

 it is entirely practicable to carry on the process without any injury, as is evidenced by the following experiment, 

 in which wood of Cuban pine in small dimensions (4 by 4) was seasoned in warm air (about 100° F.) and parts of 

 the same scantling were dried at temperatures varying from 150° at the entrance end to 190° F. at the exit' 



i 



Bending strength. 



Compression 

 strength. 



Absolute. 



At elastic limit. 



Mean of material not kiln-dried {reduced to 15 per 



Lbs. per xq. in. 

 12, 200 

 11, 500 



Lbs.pert.q in. 

 9,070 

 9,180 



Lbs. per sq. in. 

 7,630 

 8,550 







Well-constructed " blower kilns," where the hot air is blown in at one end and escapes at the other (this latter 

 always the entrance end for the material), are giving satisfaction. The best kiln, however, seems to be one in 

 which ample piping in the kiln itself insures sufficiently high (up to 180° F.), uniform temperature in all parts of 

 the kiln, and where the circulation, promoted by a suction fan, is moderate and under perfect control. In such 

 kilns even timbers of large size can be dried satisfactorily with a temperature not over 150° F. 



EFFECT OF HIGH-TEMPERATURE ANI> HIGH-PRESSURE PROCESSES. 



For some time a process employing high temperature under high pressure (temperature over 300 u F., pressure 

 150 pounds) has been discussed and applied, claiming as a result of the treatment (1) increase in strength; (2) 

 increase in durability ; (3) absence of shrinkage. 



The result of a series of experiments in which a number of scantlings of longleaf pine, one-half treated, the 

 other untreated, is as follows: 



Treated. . . 

 Untreated 



Bending 



strength. 



Compression 

 strength. 



Lbs. per sq.in. 

 7,770 

 12, 340 



Lbs. per sq. in. 

 5,600 

 7,400 



The same difference in favor of the untreated material obtained in every single case. 



The chemical analyses performed on wood lying side by side along the same radius, being of the same annual 

 riugs and same position in tree, gave the following : 



Per cent of rosin and phenols calculated to dry tveight of wood. 





Tree No. 475 



Tree 2To. 476. 



Average of both. 



Treated. 



Untreated. 



Treated. 



Untreated 



Per cent. 

 1.23 

 1.93 



0. 083 

 0.058 



Treated. 



Untreated. 



Rosin : 



Heartwood 



Per cent. 

 1.21 

 8.35 



0.061 

 0.290 



Per cent. 

 2 05 

 10 58 



0. 083 

 0.180 



Pei cent. 

 1.22 

 2.23 



0.045 

 0.070 



Per cent 

 1.22 

 5.29 



0. 053 

 0.180 



Per cent. 

 1.64 

 6,26 



0,083 

 0.119 



Phenols : 



Sap wood 



Heartwood 





Ic appears that the protective rosin is rather decreased by the treatment, and the antiseptic phenols not 

 increased in an adequate amount to be of value since it requires at least 20 times as much heavy oil in wood 

 impregnation to be effective. It is, however, possible that the change of color due to the process may be accom- 

 plished and be produced by the formation of empyreumatic bodies (allied to the humus substances) which may act 

 as preservative against the attacks of fungi. 



The claim that the shrinkage of the wood is favorably influenced by the process was not sustained by a series 

 of experiments with oak and pine, which showed that the treated wood absorbs water from air or in the tub, swells 

 and shrinks in the same manner and to about the same extent as the untreated wood. 



EFFECT OF IMMERSION ON THE STRENGTH OF WOOD. 



The notion frequently expressed is that "soaking wood by floating, rafting, etc., reduces its tendency to decay 

 and shrinkage, but injures its strength." The same was claimed for boiling or steaming preparatory to bending. 

 The last position was disproved by Peter Barlow in the first quarter of this century. The following figures (results 

 of an experiment involving several hundred separate tests) disprove the former assertion. 



