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Correcting W^oocTs Infirmities 



When nature's open air laboratory, wliich uses sunsluno, water, 

 .arbon, and other things, discovered how to make wood, it was 

 a great discovery; but there were defects, things left incomplete, 

 and it is man 's job to finish the product. Wood "is far from perfect 

 t'rom the standpoint of man's utilization. It has three serious 

 shortcomings, which may bo called its infirmities, and these have 

 always limited the use of the material and caused bother, worry, 

 and expense. 



These infirmities are decay, distortion, and combustibility; that 

 is, wood will rot, it will warp, and it will burn. If these unde- 

 sirable characteristics were lacking, wooden structures would last 

 like stone; but they are not lacking, and the modern problem is 

 to correct them as far as possible. There is no new story to be 

 told regarding efforts to cure these defects; but there is con- 

 stantly something new in successes achieved. Men are learning. 

 They are profiting by experience, and the advance in scientific 

 investigation is constantly opening new fields and showing the 

 way to reach better results. 



There is little that is mysterious about decay, at- least as to 

 its immediate cause. It is brought about by the activities of 

 plants of a low order called fungi which take root in the fibers 

 of the wood and there grow and send their roots or stems through 

 the substance, using up the starch, sugar, and other soluble mate- 

 rials, and breaking the minute structures to pieces in order to get 

 this food. The word ' ' decay ' ' means ' ' falling apart, ' ' and that 

 is exactly what happens. The binding substances that hold the fibers 

 together are eaten away, and the wood simply falls apart, and is 

 ' then said to be rotten. 



This proneness to deteriorate may be largely corrected. The 

 pores of the wood can be filled with poisons, by immersing it in 

 creosote or other preparations; and when the decay -producing plants 

 attempt to enter, they encounter the poisons, and are killed. As 

 long as they can be kept out, wood cannot rot. There are many 

 timber-treating plants in this country where this is done, and 

 several processes by which it is accomplished. It is not necessary 

 so to treat timber which is to- be kept in the dry, because decay 

 cannot attack in the absence of dampness. Practically all of the 

 wood that has grown on earth, up to recent times, disappeared 

 through the agencies of decay. That which was destroyed in other 

 I ways was relatively small ; but fire is next to decay as a destroyer. 



Wood's inflammability is at the present time a serious weakness. 

 It catches fire and burns. That which is safest from decay because 

 of its dryness, is most likely to burn. Methods of fireproofing 

 have been discovered. The processes are generally more expensive 

 than are those which suffice to hinder decay. A different enemy 

 must be combatted. Burning is a chemical process. It acts quickly. 

 Decay causes wood to "fall apart;" combustion causes it to "fly 

 apart," and return to its chemical elements at once. Decay acts 

 during years; burning is completed in a few minutes. 



Wood may be given chemical treatment which will greatly lessen 

 its liability to burn. It cannot be made absolutely fireproof; but, 

 I as in the case of decay, its inherent infirmity may be largely cor- 



rected. That is what is being done. 



The third weakness of wood is its tendency to distortion. It 

 checks, shrinks, and swells, but complete destruction is seldom 

 reached. This is the hardest thing about wood to be corrected. 

 Attempts have been made for hundreds of years. The seat of 

 the trouble lies in the structure of the wood. It is a substance 

 of the most complex character. There is hardly anything made by 

 man that -will compare with it. The unaided eye sees rings, bands, 

 pores, and rays. The lens increases their number and multiplies 

 the details; but the high power of the compound microscope reveals 

 wonders in the minute structure of wood which otherwise are totally 

 beyond the reach of the eye. Yet the microscope does not go to 

 the bottom. If it did the real cause of the shrinking and swelling 

 of wood could be seen, because the ultimate elements would show 

 what takes place when water enters the structure or is withdrawn. 



That is a thing which is not understood — why wood swells when 

 water enters and shrinks when water is taken away. It is known 

 that it does so, but why is another matter. 



Investigators have theories. It is believed by Karl WiUiam 

 Nageli, the Swiss botanist, that the ultimate particles of wood 

 substance are crystals, fitting together like stones in a wall, and 

 that water forces its way between the crystals by means of surface 

 tension or capillary attraction, and in so doing it pushes the 

 crystals apart, causing the wood to swell. When the water is 

 withdrawn, the crystals settle together again, and the wood shrinks. 

 This is theory only. No microscope has ever yet been made power- 

 ful enough to reveal the crystalline structure of wood, if it has 

 such structure; but as a theory, it is a cause which explains the 

 universal property of wood to shrink and swell upon changing its 

 moisture contents. 



Men have experimented for centuries to discover methods of 

 rendering wood proof against shrinking and swelling. Oils and 

 paints help, because they tend to keep water out, or to lock within 

 what is already there. In numerous instances it is impracticable 

 to oil and paint the wood, and even where it can be done it is 

 only partly successful. Long-continued air-seasoning is beneficial. 

 There is no doubt that such treatment lessens wood's tendency to 

 shrink and swell. Experience long ago showed such to be the case. 

 Old-time hatters air-dried their yellow poplar several years before 

 they shaped it into blocks, curling boards, and patterns. Nearly 

 two hundred years ago Mark Catesby -wrote that red gum had to 

 be air-dried during ten years to make it perfect for joinery. 



Why does air-drying during a long period change wood so that 

 water partly loses its power to swell it? No man knows; but 

 there must be a reason. If Nageli 's theory of the crystals is cor- 

 rect, it may give a hint. Possibly the long-continued and slow 

 contraction of the substance in some way locks the crystals to- 

 gether so that water cannot so easily force its way between them 

 to pry them apart and produce swelling. 



Steaming wood is known to produce a similar result, particularly 

 if the steam is applied at a temperature considerably above that 

 of boiling water, and is given sufficient time to penetrate. Shrinking 

 and swelling are decreased in a marked degree. Again, it must 

 be confessed that there is no definite and precise knowledge of 

 why this result is produced. The microscope does not seem to 

 reveal it, and chemistry does not; but if the Nageli theory offers 

 a possible explanation in the case of slowly air-dried wood, there 

 is no reason why it will not apply in steam seasoning also. The 

 application of moist heat, forced through and through the cellular 

 structure, may solder, as it were, the (supposed) crystals together, 

 or fix them in some other way so that water cannot come and go 

 between them freely as before, and, of course, shrinking and swell- 

 ing is proportionately lessened. Any diminution in the tendency 

 to swell and shrink will of necessity decrease the tendency to check, 

 for the latter depends absolutely upon the former. 



The science and processes of correcting the infirmities of wood 

 are as yet only vaguely understood. There are many workers, 

 numerous investigators, and a few discoverers; but those who know 

 the most claim to be nothing more than amateurs, feeling their 

 way along from point to point, but constantly gaining a little. 

 The engineer who treats wood to lessen its decay will not be 

 satisfied until he has discovered a material or invented a process 

 by which the timber can be so completely impregnated with pre- 

 servatives that fungus will attack in vain, and decay will act only 

 slowly and after long periods. Fireproofing processes must not 

 only be made more effective than they now are, but must be cheap- 

 ened in order that use may be widely extended. The shrinking, 

 swelling, and checking of wood will be brought completely under 

 control before manufacturers will be satisfied with what they are 

 able to do. Every woodworker and student of timber economics 

 knows how far short of that stage of perfection the present prac- 



