STRENGTH OF TIMBER TREATED 



WITH PRESERVATIVES || 



Effect of Preliminary Steaming, and of Different Preservative 

 Chemicals and Processes Upon Both Green and Seasoned Timber 



"VY7ITH the increasing use of timber, 

 preserved in one way or an- 

 other against decay and fire, it is im- 

 portant to determine the effect which 

 the preserving process has upon the 

 strength of the preserved timber. 

 Many engineers believe that creosoted 

 timber is more brittle and less capable 

 of withstanding strains than the same 

 timber before being treated with creo- 

 sote. This is particularly true with 

 bridge timbers and piling. 



Actual tests are necessary to deter- 

 mine what relationship exists between 

 the preservative process and the 

 strength of the timber. Most of the 

 tests hitherto made with preserved 

 timber were made by comparing re- 

 sults on treated sticks with results on 

 untreated sticks. In many instances 

 these turned out in favor of the 

 untreated timber. The reason why 

 such tests are unfair to the preserva- 

 tive is that in the process of preserva- 

 tion two factors enter : ( I ) The actual 

 process of impregnation with a pre- 

 serving substance, and (2) the prelim- 

 inary processes of steam seasoning, in 

 the majority of treating plants in the 

 United States. A piece of timber sub- 

 sequently treated with creosote may be 

 steamed to such an extent that the 

 timber becomes exceedingly brittle. 

 This, obviously, will be the fault of the 

 steaming and not of the creosote. 



Timber preservation divides itself 

 broadly into three stages: First, the 

 preliminary preparation; second, the 

 actual preservative process, and, third, 

 the treatment of timber following 

 preservation. The final strength of 

 the timber may be influenced material- 

 ly by each of the stages. 



The Bureau of Forestry has erected 

 an extensive plant on the grounds of 



the St. Louis Exposition for carrying 

 on a series of investigations of the 

 methods for preserving timber, and of 

 the influence various preservative pro- 

 cesses have upon the strength of the 

 timber. These investigations have 

 been organized and outlined by Doctor 

 Herman von Schrenk and Doctor W. 

 K. Hatt, of the Bureau of Forestry. 



This general plan was pursued dur- 

 ing the last few months at the timber 

 treating and testing station at St. Lou- 

 is in accordance with the following 

 outline : 



(1) To determine the effect of the 

 preliminary processes, such as steam- 

 ing, on the mechanical properties of 

 the timber. 



(2) To determine the effect of pre- 

 servatives on the strength of timber, 

 eliminating the effect of the prelimi- 

 nary processes. 



In order to determine the effect of 

 these factors, the program was divided 

 into two parts part I , the effect of the 

 preliminary process, and, part 2, the 

 effect of preservatives. 



The effects of the preliminary pro- 

 cess were determined only on loblolly 

 pine. Both green and seasoned timber 

 was used in determining the effect of 

 preservatives. The preservative fluids 

 investigated included only creosote 

 and zinc chlorid. 



In making comparative strength 

 tests of treated and untreated timbers, 

 it is necessary to eliminate as far as 

 possible the variations due to the great 

 differences in quality of individual 

 pieces of wood. This was accomplish- 

 ed in this case by using n-foot tim- 

 bers cut at the same time from one for- 

 est site. In testing the influence of 

 preliminary processes of seasoning, a 

 three-foot section was cut from one 





