Wood Preserving Department 



The Modern Application of Wood Preserving Methods I'arious Treatments and the Uses of Treated Woods 



By E. a. Sterling 



[In this department each month will be given the best information regarding all phasfes of wood treatment by preservatives 

 and the uses and values of treated woods, this having become an essential feature of conservation. The Editor will welcome 

 any inquiries.] 



THE universal use of wood makes the modern 

 practice of preserving it against decay of wide 

 interest. The saving which is effected, and the 

 extension of the use of wood because it can be made 

 permanent, concerns the consumer, the lumber producer, 

 and the wood preserving interests on common ground. 



The decay of timber has been a problem since time 

 immemorial, yet wood so far surpasses all other struc- 

 tural materials in workable qualities, availability, beauty 

 and convenience that it has held its own through all the 

 years. Under modern competition with other materials 

 it still retains the leading place, and by proper preserva- 

 tive treatment as now developed the renewals necessi- 

 tated by decay can be greatly reduced or eliminated. 

 Permanence and improved service become a matter of 

 knowledge. Information on the subject should be ex- 

 tended so that treatment can be applied where it is 

 economical or otherwise advisable. 



In this country the extensive commercial application 

 of wood preserving methods is a twentieth century 

 development. It is true that the first plants were built 

 nearly forty years ago and crude treatment applied even 

 earlier ; yet only during the last fifteen years has there 

 been rapid advancement. In Europe wood preservation 

 has been an accepted practice for three-quarters of a 

 century, with the recorded experimental use of many 

 preservatives and processes extending back to 1657. 

 Even in the dim ages of Egyptian supremacy, it is 

 apparent that ways and means had been found for pre- 

 serving animal and vegetable tissues indefinitely ; while 

 during the early Greek and Roman civilization oils were 

 applied to preserve their statues and bridges. 



The modern application of wood preservation depends 

 on the economic advantages and on knowledge of the 

 possibilities and methods. During the years of rapid 

 industrial expansion and of cheap and abundant supplies 

 of lumber it was cheaper to renew the wood which 

 decayed than to incur the greater initial expense of mak- 

 ing it permanent. These conditions no longer hold, 

 hence the adoption of wood-preserving processes, first 

 by railroads for crossties and bridge timbers; later for 

 a great variety of construction timbers which are subject 

 to decay. The next step is to the home builder and retail 

 trade. 



Despite the fact that several hundred different ma- 

 terials have been tried and advocated for preserving 



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wood, the cheapest and most effective in use today have 

 been known and used for many years. These are coal 

 tar creosote and zinc chloride, each having been brought 

 to us from Europe. Strangely, both were invented or 

 proposed in England in the same year 1838. New pre- 

 servatives are continually being produced and promoted, 

 and while some of them have merit, the two old stand- 

 ards remain supreme in point of consumption and 

 general acceptance. The test of time is the essential 

 proof of efficiency, and other preservatives may ulti- 

 mately make good. To merely prevent or defer decay 

 is not enough ; the ideal preservative must be permanent, 

 penetrate the wood readily, and not be too costly. 



The nature of decay is understood by scientists, but is 

 not of general knowledge by the public or even by every- 

 one interested in the wood-preserving business. As 

 applied to wood decay is caused by vegetable organisms 

 known as fungi. These propagate by means of inicro- 

 scopic spores, which are equivalent to the seeds of 

 plants. Being produced in enormous numbers and 

 blown about by the wind, they are present everywhere. 

 When they find lodgement on wood they develop a 

 growth of microscopic threads which penetrate the 

 tissues of the wood and cause disintegration. After a 

 period of growth they produce fruiting organisms which 

 constitute the common fungus growth seen on decayed 

 wood. 



In order to develop, the fungi must have moisture, 

 favorable temperature, air supply, and food. The latter 

 is furnished by the wood itself and the other factors 

 are present in practically all outdoor conditions. Pre- 

 servatives prevent the development of the organisms of 

 decay through the double function of being antiseptic 

 or toxic and killing or poisoning the spores, and by at 

 least partial elimination of moisture. The antiseptic 

 feature is probably the most important and while inert 

 oils, which to an extent waterproof the wood, will pre- 

 vent decay for a time, they are not certain or permanent 

 in their action. Coal tar creosote is both antiseptic and 

 moisture excluding to a marked degree. It also has the 

 further advantage of permanence. Zinc chloride is 

 effective mainly through its poisoning action to low 

 forms of vegetable growth and from our present knowl- 

 edge is of greatest efficiency in regions of low rainfall or 

 in dry situations. 



Preservatives are applied to wood in several different 

 ways, the more common forms of treatment being pres- 



