22 



HARDWOOD RECORD 



already been imported into this country, a great many others of 

 lesser importance come to our markets. The satinwoods, lancewoods, 

 zebrawoods, and purplehearts, all of which are produced by no less 

 than six different trees, form a part of our timber trade at the 

 present time, and the number of kinds and quantities will continue 

 to increase from year to year. 



Practically no reference has been made to the timber on the Andes, 

 but while the whole chain is densely wooded these forests are at 

 present inaccessible. Peru, Ecuador, Bolivia, and Chili have great 

 forest wealth, but the timber will be needed for home consumption 

 as soon as it can be made available. 



L. L. D. 



XJM^jia^BSTOatTOTOMjM^W^^ 



Strength Affected by Moisture 



The fact is well known that a piece of paper soaked with water 

 loses strength and becomes soft. If it is dried in a rather high 

 degree of heat it regains much of its former strength and stiffness, 

 and may in some cases become stronger than it was before the soak- 

 ing. Wood follows the same rule in many respects if not in all. 

 Wood and paper are composed of practically the same material, but 

 the former has more structure; that is, the particles which compose 

 a piece of wood are arranged somewhat differently from those which 

 make a sheet of paper. However, the behavior of the two pieces of 

 material is much the same when they are soaked and dried. 



It is impossible to reason out the causes which produce these effects, 

 or to tell why certain effects follow certain causes, in soaking and 

 drying wood. It is a matter to be determined by actual tests. Some 

 traces of laws may be found, which seem to govern the matter, but 

 thus far the only known way of determining what effect moisture or 

 drying will have on wood is to try it, to make tests, and conduct 

 experiments. On this subject, Harry Donald Tiemann in his treatise, 

 "The Strength of Wood as Influenced by Moisture," says: "Since 

 wood is a very complex structure, composed of many substances, con- 

 cerning the exact chemical and physical nature of which very little 

 is known, it is impossible to theorize with any degree of certainty 

 as to the influence of moisture, heat, and other intrinsic factors. The 

 laws are extremely subtle, and can be determined only empirically 

 from a large number of actual tests." 



No fact is better known than that dry wood is stronger than green. 

 The difference is very great with some woods, and spruce is one of 

 the best examples. A dry stick of spruce may be four times as 

 strong as a green piece of the same size. With the majority of 

 woods, however the difference is not so great. It has been estimated 

 that the strength of high-grade carriage stock is increased from 50 

 to 350 per cent by drying. It is not definitely known why seasoning 

 increases the strength of wood, but a good many interesting things 

 have been found out which may ultimately explain all about it. 



Moisture exists in green wood in two conditions. Some is contained 

 in the hollow cells, in the same way that honey occupies honey comb, 

 or that liquid is contained in a bottle. Other water exists in the walls 

 of the' cells. 



It is the water in the cell walls — not that in the hollow interior of 

 the cells — which influences the strength of wood. If the cell walls 

 are saturated, the wood is weakened; when these walls become dry, 

 the wood is strong. When the cell walls have become saturated they 

 will absorb no more water, though the cell cavities may continue to 

 take it in. 



AVheu dry wood is exposed to the air it absorbs moisture to the 

 extent of from eight to sixteen per cent of its dry weight, and in 

 so doing it becomes weaker than it was in its dry condition. 



When wood has once been dry and is brought back to the wet 

 condition by soaking, it is weaker than it was in its green state. 

 Wood which has been kiln-dried in moist heat of about 130 degrees 

 F., will lose from fifteen to eighteen per cent of its original green 

 strength, when it is resoaked. 



"Experiments," says Tiemann, "indicate that drying wood at 

 high temperatures, either in steam or in dry air, produces the fol- 

 lowing results: (1) It permanently reduces its moisture content 

 below that of ordinary air-dried wood when again exposed to the air, 

 at the same time rendering it less hydroscopic, so that it is less sus- 

 ceptible to changes in the humidity of the air; (2) the moisture con- 

 dition of the fiber saturation point i* changed, being reduced by high 



temperatures with dry air or superheated steam; (3) the strength 

 of the wood is increased, except in the resoaked condition. Whether 

 the increase in strength is due to the reduction in hygroseopieity or 

 to physical changes is of secondary importance, since in either case 

 the strength under like atmospheric conditions is increased." 



The effect of moisture on the strength of wood presents an inter- 

 esting example of the acceptance of a fact before its cause is clearly 

 understood. The cause will doubtless be discovered sometime, for 

 numerous investigators are patiently working their way toward it,, 

 thus illustrating Tennyson's summary: "Science moves but slowly, 

 slowly creeping on from point to point. ' ' 



Trade-Marking Lumber 



The Kraetzer Company of Chicago, manufacturer of the Kraet- 

 zer preparator, has registered in the United States patent ofiSce 

 as a trade-mark the term " Kraetzer-cured Lumber," as depicted 

 in the accompanying illustration. It is expected that manufac- 

 turers who emi)loy this system of treating lumber to insure its 

 quick and accurate seasoning will rubber stamp or brand their 

 lumber with this trade-mark: 



GT/ —I TRADE 



Kramer- 



cure 



LUMBER 



REC31STERED IN U S. PATENT OFFICE 



This sj'stem of lumber treatment is resulting in no inconsiderable- 

 popularity of several woods whose refractory qualities did not 

 readily lend themselves to ordinary lumber drying practice, but 

 through this process are very much improved in quality, to say 

 nothing of the fact that thoy are devoid of stain, warp, twist and 

 other seasoning defects. 



Recently a Chicago furniture manufacturer has put some Kraet- 

 zer-cured 2Y/' red and sap gum to a pretty severe test to ascer- 

 tain if it would stand up under rigorous treatment. He says when 

 the lumber arrived he found it was the prettiest looking stock he 

 ever saw, that the sap was absolutely free from stain, the lumber 

 dry and entirely unchecked. He cut several pieces about 4' long, 

 into rococo shape— something like the letter "S" — soaked them 

 in water over night and laid them on hot steam pipes for two days. 

 Two other pieces that he did not soak were also laid on steam pipes 

 for the same length of time. Under this severe' treatment, the- 

 lumber showed no blemish whatsoever, either in warp or check. 



Recent drying tests on one-inch hard maple steamed in the 

 Kraetzer apparatus show, under normal drying conditions in the 

 open, a reduction in weight of 28% per cent without seasoning 

 defects, in two weeks' time, and one-inch birch, a reduction in 

 weight of 29% per cent in the same length of time. This weight 

 is less than normal shipping dry weight after months of air drying 

 without the use of the steaming apparatus. 



At the present time The Kraetzer Company is shipping one of 

 these equipments every week, and is still quite a ways behind its 

 orders. The apparatus seems to be in growing favor everywhere, 

 but the larger number of installations at the present time are being 

 made in Arkansas, Louisiana and other southern states. 



