48 



HARDWOOD RECORD 



and that the various substances which con- 

 tribute to the growtli of the tree have no value 

 in the eventual utilization of the material. 

 If this be true, and there is no evidence to 

 I he contrary, it would seem that the logical 

 way to handle green lumber before an attempt 

 is made to either air-dry or kiln-dry it would 

 be to render soluble and release the various 

 liquid and semi-liquid materials that are in- 

 \olve<l in the vessels contained in the fibers 

 of the wood. 



There are certain either well or compara- 

 tively well-known facts eoueerning aids for 

 the prompt drying of lumber in both air- 

 . Irving and kiln-drying. Some of these may 

 he briefly summarized: — 



1. It is a well-known fact that white piue, 

 poplar and several of the Pacific coast woods, 

 after being water soaked for a considerable 

 period, dry much more quickly and more 

 satisfactorily than when not floated or held in 

 the log pond for a considerable time. 



2. It has been demonstrated that green 

 cypress piled on sticks, enclosed in a steam 

 box and subjected to several hours of exhaust 

 or live steam, will show a lightening in weight 

 oJ: from one thousand to fifteen hundred 

 pounds to the thousand feet. 



3. It has been demonstrated in the more 

 recent modification in dry-kiln processes that 

 lumber placed either in a steam box before 

 entering the kilns or subjected to exhaust 

 steam, after being placed in the kilns, ma- 

 terially lessens the time for kiln-drying and 

 that the lumber is less liable to case-harden- 

 ing, cheeking and splitting. 



4. In an experience covering more than 

 thirty years it has been demonstrated that 

 steaming mahogany, oak and black walnut 

 under a moderate pressure for a limited time 

 in no wise injures the quality of the wood 

 fiber, but breaks up the cellular structure of 

 I he wood and contributes materially to the 

 shortening of time in which the lumber may 

 be air or kiln dried ; and furthermore im- 

 jjroves the color and texture. 



5. It has further been demonstrated that 

 treating luraljer piled on sticks in a steam 

 cylinder with a moderate pressure and lim- 

 ited time renders it possible to kiln-dry lum- 

 ber thus treated in from twelve to thirty-six 

 hours, and that it will reduce the time for air- 

 drying to from thirty to sixty days. Fur- 

 thermore, that in lumber thus steam-treated 

 future staining is eliminated; the work of 

 borers is eliminated; the color of the wood 

 is distributed and rendered approximately 

 uniform; warping, twisting and buckling are 

 practically eliminated; splitting and checking 

 are minimized ; the time for rendering green 

 lumber dry is reduced more than one-half ; 

 and that future shrinking and swelling are 

 very slight under varying atmospheric condi- 

 tions. 



This is about all the lumberman or the 

 scientist knows on the subject. The experts 

 of the United States Department of Forestry 

 will tell you that their experiments under 

 varying conditions indicate that steamed lum- 

 ber tends to dry much more rapidly than 



green wood unsteamed, and that the same is 

 true of green wood soaked for some time in 

 water. Their experimental tests have shown 

 that large timber such as railroad ties may be 

 steamed at twenty-pound pressure for as 

 much as four hours without material depre- 

 ciation of strength. The physical effect which 

 they contend appears to take place is a slit- 

 ting of the cell walls of the wood, and re- 

 leasing their contents, which begins at a com- 

 paratively low pressure of steam and increases 

 as the temperature and pressure is raised. 



Almost nothing is known of the chemical 

 changes which occur in wood when steamed 

 under pressure, except that certain volatile 

 materials such as turpentine pass off. It is 

 also quite certain that the starches are par- 

 tially converted into sugar, which, being solu- 

 ble, naturally in part would leak out of the 

 wood. It is likely that tannic acid may be 

 partially decomposed. 



At the present time those in charge of the 

 new wood-treating laboratory of the United 

 States Department of Agriculture at the Uni- 

 versity of Wisconsin at Madison, are at work 

 attempting to figure out the fundamental laws 

 underlying the drying of wood. As their 

 analysis is exhaustive it will take some time 

 to work out these scientific deductions. 



In a practical way there is nothing abso- 

 lutely new either in the treatment of lumber 

 Vi'ith steam without pressure, or in steam- 

 tight cylinders with pressure. It is well 

 known that in wood subjected to an excessive 

 steam pressure and for a considerable period 

 of time the wood fiber is disintegrated or 

 pulped, or even under less pressure that 

 the strength of the piece is impaired. Even 

 less time and steam pressure will release 

 the coloring matter contained in the wood and 

 render it pale and colorless and deficient in 

 character, but it is a matter of demonstra- 

 tion that wood given live steam under a pres- 

 sure of from twenty to twenty-five pounds 

 and in time varying from five to fifteen min- 

 utes, according to kind and thickness, that 

 the coloring of the wood is distributed, equal- 

 ized and improved, rendering it approximately 

 unifurm; that the strength of the wood is 

 unimpaired; and that its milling and finishing 

 qualities are -materially -bettered. 



Undeniably, there are quite a number of 

 kiln-drying systems in use at the present time, 

 which, if employed on lumber steamed as in- 

 ilicated, would show competent dry-kiln re- 

 sults in less than one-half the time that it 

 now- takes to season lumber, but the point at- 

 tempted in this article is to show the necessity 

 of properly preparing lumber for seasoning 

 before it is air or kiln dried. 



This process should particularly appeal to 

 manufacturers of lumber in the lower Mis- 

 sissippi valley. Here climatic conditions are 

 very serious for either air-drying or kiln- 

 drying. Manufacturers report that after the 

 lumber is put into pile green on mill grade, 

 the average degrading of stock when ready 

 for shipment is approximately twenty- 

 five per cent. This degrade comes about from 

 a variety of causes. Lumber in this section 



is prone to stain, to check, to buckle, to warp, 

 ti' split, and very often borers work into it 

 after it is cross-piled. In some cases stick- 

 rot sets in long before the lumber is in ship- 

 ])ing condition. It is a difficult country for 

 the operation of dry-kilns, owing to the ex- 

 cess of humidity in the air during a large por- 

 tion of the year. 



Therefore it is, that if the moderate steam- 

 ing of lumber under pressure will accomplish 

 what is claimed for it, the logical thing for 

 the manufacturer of any considerable quan- 

 tity of lumber in a good many sections of the 

 country would be to pile his lumber onto a 

 modification of a dry-kiln truck right from his 

 sorting chains, steam it, kiln-dry it and either 

 load it directly to cars or house it dead piled 

 in sheds. 



As before noted, there is nothing absolutely 

 new about this method of preparing lumber 

 for seasoning, but it has remained for A. 

 Kraetzer of Chicago to work out an econom- 

 ical system and appliances for handling lum- 

 Ijer under this process in an extremely eco- 

 nomical way. For years Mr. Kraetzer has 

 been a manufacturer of interior finish and 

 cabinet work, and he found in his experience 

 that it often happened that he was unable 

 to secure lumber of various kinds either air- 

 dried or kiln-dried that would "stand-up" in 

 liis finished work. For more than six years 

 he has been employing this system in the sea- 

 soning of practically every variety of lumber, 

 and today is willing to go on record with 

 a guarantee that by the aid of his steam- 

 ing and kiln-drying process he can satisfac- 

 torily deliver one inch red or white oak, red 

 gum, Cottonwood, birch or maple from the 

 green state to a thoroughly kiln-dried condi- 

 tion in less than half the time required by 

 any other process, and that this lumber 

 will be unimpaired in texture, its milling 

 qualities will be improved; the color will 

 be uninjured and uniformly distributed, and 

 when put into cabinet work the shrinking or 

 swelling will be so infinitesimal that it will 

 never break a glue joint and will stay abso- 

 lutely in place. He will further guarantee 

 that he will accomplish this result without 

 case-hardening, honeycombing, checking or 

 splitting. 



For those who prefer to air dry lumber, 

 rather than employ dry kilns, the system will 

 commend itself, as lumber thus steam treated 

 will dry out to less weight and in perfect 

 shape in 30 to 60 days time — or in one-fourtb 

 the time that unsteamed lumber can be 

 seasoned. 



Mr. Kraetzer has a modest plant for the 

 treating of lumber under his system at his 

 Chicago woodworking factory, and is pre- 

 pared to demonstrate that he can fulfill all 

 the claims he makes for it to anyone interested 

 in installing a similar equipment to handle 

 an output of from twenty-five thousand to one 

 hundred and fifty thousand or more feet of 

 lumber per day. 



In connection with this work the inventor 

 has fully protected himself with patents on 

 his steaming appliance, and beyond that has 



