HARDWOOD RECORD 



71 



Common Sense in Lumber Drying 



Referring to the article iu the last issue of 

 tlie RccoKD, entitled ' ' Common Sense as Ap- 

 plied to the Seasoning of Lumber," the 

 editor of the Record addressed the follow- 

 ing letter to leading manufacturers of dry- 

 kiln equipment throughout the country: 



Chicago, August 10. 



GENTLEiiEN : I wisli to fall your attention to 

 an article in issue of Hardwood Recokd of cur- 

 rent (late, of which we will mail you a copy, 

 entitled •■f'omniou Sense as Applied to Season- 

 in;: of Lumber." 



Kindly review this story ; analyze it, and if 

 you think it wortli while, should be glad to 

 liave your deductions for publication in Hard- 

 wood Record. 



What I particularly want to know is, if you 

 liolievo that the steaming of lumber will assist 

 the quality, speed and economy of kiln drying 

 |)rocesses. Very sincerely yours. 



Hardwood Record, 



H. H. Gibson. 



Iu reply to this communication the fol- 

 lowing answers have been received. The Rec- 

 ord believes that the steaming of lumber under 

 prefsure constitutes a distinct advance iu 

 Imnbcr drying processes; that it will not only 

 leave the wood unimpaired in quality, but 

 materially improve it; will shorten the time 

 for either air or kiln-drying fully one-half 

 aud, in addition, effect a material economy 

 in cost. 



The letter referred to was addressed to 

 various dry-kilu companies with the idea that 

 they inight have something of distinct value 

 to offer either in commendation or condem- 

 nation of the system referred to. These let- 

 ters are therefore printed, without comment, 

 to aid the lumber fraternity iu making its 

 own deductions on the subject : 

 Mr. H. H. Gibson. Hardwood Record, Chicago. 



Hear Sir : Replying to yours of the 10th, 

 would say. we have carefully read your article 

 entitled "Common Sense as Applied to Seasoning 

 Lumber." and consider the same very well writ- 

 ten. 



The article is inaccurate in one statement, 

 viz.. that all kiln concerns put lumber through 

 their processes without reference to its kind or 

 nature. As one exception, we furnish most care- 

 ful instructions for the drying of various kinds 

 of wood, and we know that other kiln concerns 

 are working along this line. 



We do believe that vapor assists in the 

 rapid drying of lumber and improves the con- 

 dition of the product. Instead of calling it 

 steaming, however, the only word that seems 

 to fit is "humidifying," much as you would place 

 a man in a vapor bath to start the perspiration. 

 Steam, under pressure, has a searing effect, but 

 as a vapor at high temperature it penetrates. 



We have honeycombed and casehardened lum- 

 ber many times in confined steam under pressure 

 of from 10 to 25 pounds, and this result was 

 ■produced iu a very short time. That is why 

 we abandoned this method for the vapor method 

 in use in our spraying compartment. 



For us to reply to the above mentioned 

 article for publication, would mean the dis- 

 closnre of the greatest thing that ever happened 

 in the way of lumber drying, and these are the 

 things that we tell to our customers only after 

 we have them under contract. 



Wo thank you for calling our attention to the 

 article, and will carefully watch the develop- 

 ment of this process, to see if it follows the 



same course as that taken b^- us in arriving at 

 our present state of efficiency. Yours truly, 

 GiiAXD Rapids Ve.neer Works, 



F. H. Kelly. 

 Hardwood Record, Chicago, 111. 



Gentle.men : Replying to your favor of the 

 tOth, we have just read the article in your 

 paper, entitled "Common Sense as Applied to the 

 Seasoning of Lumber." 



We have found, in our experience, that the 

 majority of people do not favor steaming the 

 lumber if they want the life of the stock and 

 the strength of it retained. As is well known, 

 that process is an old one ; nothing new about 

 it, and anyone that has tried it knows that the 

 lumber is not as strong or elastic as that dried 

 witliout steaming, unless they are very particu- 

 lar what pressure and liow long to steam it. 

 We have, however, during our experience, put 

 in steaming boxes in the receiving end of our 

 kiln, to steam oak, for those who wanted to dry 

 it green from the saw. in order to extract the 

 sap and tannic acid from it, so as to dry it 

 without turuiug dark color. Of course, every- 

 body knows that it is impossible to kiln dry 

 green oak without first steaming it or pile it on 

 sticks for ninety days or more, on account of it 

 turning dark, honeycombing and checking. Any- 

 one of experience also knows that air-dried hard- 

 woods are stronger and better than kiln-dried. 

 The capital tied up in air-drying is what kills 

 that process. 



You will find most every millman to have 

 a different opinion on the subject, both as to 

 manner of drying hardwoods and the length of 

 time required, regardless of any system. 



We have been successful in convincing t!>n- 

 dreds to adopt our system and they all say OEr 

 claims were fulfilled. Our patent regulators prac- 

 tically hermetically seal a kiln, thereby retain- 

 ing the moisture or humidity which accomplishes 

 the same quick results as a steam spray pipe 

 in a wide open flue kiln. 



We built six or seven steel tubes 100 feet long 

 each, eight or ten years ago, for the New York 

 Fire-proof Wood Company, to steam their lum- 

 l)er. They put 3 00 pounds' pressure on the stock 

 for several hours. The result was the life and 

 strength of the lumber was completely destroyed. 

 Steaming hardwoods under a low pressure heats 

 it through arfd through quicker, but the trouble 

 with the average millman is he is so apt to 

 steam it too much, which makes It so that many 

 of them that are equipped for it do not do it. 

 Very truly yours. 



The E.merson Dry Kiln Company, 



H." W. Wofiford, Propr. 

 H. H. Gibson, Editor Hardwood Record, Chicago. 



Dear Sir : I have yours of August 10, also 

 copy of Hardwood Record, with article on lum- 

 ber drying, entitled "Common Sense as Applied 

 to the Seasoning of Lumber." The article is so 

 iuaccurate that tiie reply must necessarily be 

 of some length, but the main facts can be an- 

 swered in few words. 



The evaporation of a pound of water, or 

 liquid, in lumber called sap. requires exactly the 

 same amount of heat, regardless of time or tem- 

 perature. The only thing that may be saved 

 in lumber drying is the waste. The air should 

 be held moist enough to hold back the outside 

 drying while heating the inside of the lumber. 

 A cubic foot of steam, 212 degrees, at atmos- 

 phere, holds practically the same amount of mois- 

 ture as a cubic foot of air at the same tempera- 

 ture at saturation ; therefore there is no differ- 

 ence between steaming lumber and subjecting it 

 to moist air near the point of saturation. Heat 

 is the main factor in the force of expelling. 



The day is coming when types of dry kilns 

 will have no bearing with the purchaser. He 

 will ask but one question ; Can you maintain 

 the temperature and humidity required for my 



stoci; ■; It llie hvuiiidity can be maintained, it 

 means that the surplus moisture can be gotten 

 rid of iu exactly the amount desired. 



In what the writer of the article speaks of, 

 regarding floating of wood, the process which 

 takes place is called "osmosis," and means a 

 gradual interchange of the sap with that of the 

 river water. It Is not a well known fact that 

 such a process, while it does certainly make lum- 

 ber dry more quickly, as water is more easily 

 removed than the original water witii its mix- 

 ture of albumen and other substances, preserves 

 its strength, the facts are quite to the contrary : 

 the strength of the lumber is less, and the appli- 

 cation of steam has nothing to do with this 

 process called osmosis, as steam never pene- 

 trates lumber, it merely expels by heat or pres- 

 sure, the .sap in the cells. All the chemical 

 changes that take place are a result of heat 

 and are acconiplisbed exactly the same in moist 

 air, such as making soluble turpentine, etc. 

 Superheated steam is the quickest known method 

 of drying. This turns the sap directly into steam, 

 but can only be safely used on what are termed 

 softwoods of small dimensions. 



The greatest tensile strength in lumber is 

 not obtained by breaking the cell, but by pre- 

 serving it. Steam, when used with air, as I 

 understand the writer means in his deduction 

 No. 2, has then a drying power. Under Dalton's 

 law. that one gas may take the place of an- 

 other as though the other were not there, steam 

 and air, occupying the same space, have the 

 heat of both, aud therefore have a drying ca- 

 pacity. Therefore, lumber placed in such a 

 steam box should lessen the time of drying, inas- 

 much as it is drying while being steamed, but 

 it is also another fact that the latent heat of 

 steam cannot be obtained in full amount in di- 

 rect application as it can in radiation from 

 pipes. 



^^'hen the gentleman states in article No. 4 

 , that the quality of the wood flber is not in- 

 jured by breaking the cellular structure, and 

 that the color is improved, he will hardly find 

 any man, who appreciates the natural color of 

 the wood aud its full tensile strength, to agree 

 with him. Steam under pressure is another mat- 

 ter entirely. There we have both the heat and 

 the pressure expelling the water. Jack oak ties 

 are subjected to 300 pounds' pressure, massing 

 the wood and removing the larger percentage of 

 the sap in a few hours, therefore, it seems neces- 

 .sary to consider what you want lumber for. 

 when you disctiss its method of drying. Flooring 

 will undoubtedly resist friction longer when the 

 structure is crushed : wagon, implement, car 

 stock and the like are much stronger when they 

 are not crushed : cabinet work is not injured, 

 as a rule, when the structure is massed. There- 

 fore, the pressure of steam is the thing that 

 governs drying b.v this method. 



It is unfortunate that promoters of various 

 drying methods should advocate that everything 

 should be dried by one method. The thing that 

 makes a piece of wood warp is, either that one 

 side is dried before the other, or else that the 

 wood is cross-grained. In this latter case the 

 cell, being longitudinal to the heart, the lumber 

 shrinks toward the grain and not toward the 

 center of the board. If the board is dried in 

 moist air and held pliable, the stickings usually 

 remedy this. Another way is to flat-pile such a 

 percentage of material as may be warped. 



The statement that, at low pressure, a small 

 amount of live steam is required for steaming 

 wood, is not correct. It is a very expensive use 

 of steam where fuel has a cost. To turn the 

 steam into a cylinder, such as described, low- 

 ered the pressure, in a battery of boilers, 1.000 

 horsepower, seven pounds : this on green maple. 

 The process used on pine at a sawmill reduced 

 the pressure of a sixty-five horsepower boiler 

 forty pounds, and shortened the time of drying 



