1905 



FORESTRY AND IRRIGATION 



35 



end of each timber and sawed up into 

 test pieces, which furnished a basis of 

 comparison between ( i ) the results of 

 tests on these "control" pieces, and 

 ( 2 ) the results on test pieces taken 

 from the remaining eight-foot section 

 after the latter had been subjected to 

 the various preliminary processes in 

 the treating cylinder. 



In testing the effect of preservatives 

 themselves the entire n-foot timber 

 was subjected to the preliminary sea- 

 soning processes, after which a three- 

 foot section was cut from the end of 

 each timber. The three-foot section 

 thus having been subjected to the pre- 

 liminary seasoning processes formed a 

 basis of comparison with the remain- 

 ing eight-foot section, which was treat- 

 ed with the preservatives. In this way 

 the separate effects of the preliminary 

 processes and the effects of the pre- 

 servatives could be isolated and deter- 

 mined. 



Because of an apprehension that de- 

 fects of brittleness of treated timbers 

 might not be evidenced by the ordi- 

 nary tests under slowly applied loads, 

 provision was made for both static 

 tests and impact tests. The test pieces 

 were subjected to crossbending strain, 

 compression along the grain under 

 both static and impact conditions, and 

 under shearing parallel to the grain 

 and compression at right angles to the 

 grain under static conditions. The 

 data taken include the moisture condi- 

 tions, specific gravity, and rate of 

 growth. During the treating opera- 

 tions, records were kept of the tem- 

 perature to which the timbers were 

 subjected at all stages, the amount of 

 water lost or gained, and of the amount 

 water lost or gained, and of the 

 amount of preservatives absorbed, as 

 indicated by gross weight and subse- 

 quent chemical analyses of the test 

 pieces. 



Ordinarily the strength tests \vere 

 made immediately after treatment in 

 the cylinder. In order, however, to 

 determine what weakness might be in- 

 troduced by changes in the physical 

 condition of the preservatives in the 

 wood through lapse of time, a com- 



plete series has been set aside for sub- 

 sequent operations. An additional set 

 of test pieces has been loaded with dif- 

 ferent precentages of the strength, as 

 exhibited under the ordinary tests, and 

 this load allowed to act for long peri- 

 ods of time, the deflections being 

 measured from day to day. 



\Yhile this program is not sufficient- 

 ly advanced to allow the drawing of 

 final conclusions, yet the preliminary 

 results are fairly indicative of what 

 may be expected. It is found that the 

 steaming process weakens the resist- 

 ance of the wood fiber to both static 

 and impact loadings. It may be stated 

 that this diminution of strength is very 

 nearly in direct proportion to the 

 length of time that any given steam 

 pressure is applied. The diminution 

 of strength was found to be 25 per 

 cent, after a pressure of twenty pounds 

 was applied for ten hours to green 

 loblolly pine, and 10 per cent, when a 

 pressure of twenty pounds was applied 

 for four hours. This diminution of 

 strength increased very rapidly when 

 the pressure rose above twenty pounds 

 and amounted to about 25 per cent, 

 when a pressure of fifty pounds was 

 applied for four hours. 



It will be easily seen that when the 

 conditions of time and pressure are 

 made very severe, the conditions pre- 

 vailing in a pulp mill industry will be 

 approximated. Evidently it is well to 

 avoid when possible the use of these 

 preliminary steaming operations in the 

 wood-preserving industry. 



With relation to the effect of preser- 

 vatives themselves, the latter is distinct 

 from the preliminary process. It may 

 be said that the treatment with zinc 

 chlorid does not seem to further reduce 

 the strength of timber beyond the ef- 

 fect of the steaming process. This 

 might have been expected when it is 

 considered that the strength of the 

 zinc chlorid solution ordinarily used 

 does not exceed 2>^ per cent. The 

 strength of timber that had been treat- 

 ed with the 2. l /2 per cent, solution of 

 zinc chlorid after having been steamed 

 four hours at twenty pounds pressure 

 was the same as that of timber which 



