Wood Preserving Department 



By E. A. Sterling. 



IN this department last month the reasons for the 

 decay of timber were discussed. Since it is a well- 

 established fact that wood-destroying fungi cause 

 decay of timber, the next point is to determine what can 

 be done to prevent this destructive action. 



The first essential of a good wood preservative is that 

 it shall kill the fungous growth which causes decay or 

 make it impossible for the spores to develop. This toxic 

 quality is possessed by many chemicals or compounds, but 

 for practical purposes only a few possess the additional 

 requirements that they shall remain liquid at ordinary tem- 

 peratures, penetrate at least the outside tissues of the 

 wood, be permanent enough to give continuous protection, 

 and be safe to handle and apply. There is the further 

 economic requirement that the preservative shall be of 

 reasonable cost. 



Many hundred preservative materials have been tried 

 and abandoned because they were too expensive, or failed 

 to meet one or more of the essential requirements. Long 

 experience clearly indicates that coal-tar creosote is the 

 best genera] preservative. It comes the nearest to meeting 

 all the essentials and approaches the ideal because it pre- 

 vents decay, is lasting in its results and is not too expen- 

 sive for general use. It fails to reach perfection because 

 there is some loss by evaporation, but mostly of the 

 lighter, less valuable fractions, and it does not penetrate 

 the dense, hardwood portions of some timbers. On the 

 other hand, it is insoluble in water, remains liquid at 

 ordinary temperature and is safely used under nearly all 

 conditions. It has a strong pungent odor, but this disap- 

 pears almost entirely after exposure to the air. Creosoted 

 surfaces cannot be painted in light colors because the 

 oils stain through, but the creosote itself gives a rich 

 brown tone. 



ANOTHER preservative which is extensively and 

 successfully used is a mineral salt known as zinc 

 chloride. This also is sufficiently toxic to kill 

 wood fungi, penetrates the wood when in solution, and 

 very materially increases the resistance of wood to decay. 

 It is cheaper than creosote and would be universally 

 used except for the fact that it cannot be successfully 

 used by open-tank or brush treatment, and is not as 

 effective as creosote when applied superficially. It is also 

 soluble in water, which causes it to leach out to some 

 extent from the outer portion of the wood. 



Among many other materials which have been used 

 as wood preservatives, but which have not received 

 recognition, are tar, crude oil, linseed oil, whitewash and 

 wood creosote. With the exception of the latter, it may 

 be safely stated that they are not sufficiently poisonous, 

 do not penetrate the wood sufficiently, are not permanent, 

 or are too expensive for general use. Wood creosote has 

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qualities which indicate a preservative value, but the 

 results from its use are not fully established, nor is it 

 generally recognized as a satisfactory preservative for the 

 small consumer. 



IX the case of patented or proprietary preservatives 

 careful consideration should be given to their value 

 in relation to cost. These include chemical solutions 

 of various kinds, many of which have been quite exten- 

 sively sold. Some of them, particularly those containing 

 creosote, have high preservative value ; others are practi- 

 cally worthless, despite extravagant claims. Most of them 

 are high in cost and are rarely superior to refined or even 

 crude creosote and often not as good. As a guide in 

 considering the value of the many preservative prepara- 

 tions offered in retail quantities it should be remembered 

 that there have not been any new preservatives of estab- 

 lished value discovered or developed for many years. 

 Trade name may be used for material of great value, but 

 if this is the case, it should be ascertained whether or 

 not the principal constituent is an accepted material, such 

 as creosote. While recognizing fully the effectiveness of 

 zinc chloride for commercial use, if applied by proper 

 pressure process, the fact remains that for the small con- 

 sumer, using the open-tank or brush treatment, or for the 

 man who buys the preservative by the barrel for home 

 use, the safest and most reasonable course is to buy the 

 best creosote obtainable. This may mean buying it as 

 creosote or under some trade name, but the result is the 

 same, provided the oil is derived wholly from coal tar. 



THE many kinds and forms of timber which it is 

 desirable or economical to give a preservative 

 treatment is a large subject itself. While it has 

 been mainly the large consumers, such as railroads, which 

 have recognized and adopted wood preserving methods, 

 on the farm or around the average home, the advantages 

 are equally apparent. The economy, permanence and 

 attractiveness of many structures would be very greatly 

 increased at a distinct saving as a result of proper treat- 

 ment. Among the many classes of timber which can be 

 advantageously treated may be mentioned fence posts, 

 sills and foundation timbers, board-walks, wooden gates, 

 pickets, wind mill frames, silo staves, shingles, floors of 

 stalls, sill joists and framing under floors and timber in 

 contact with foundation or with the ground. 



ANEW idea is to paint farm buildings and similar 

 structures with creosote. It can be easily 

 applied, is absorbed by the wood and becomes 

 permanent and serves both as a paint and a preservative. 

 The same idea may be applied to garages and similar 

 small structures around city and suburban homes. 



