24 



HARDWOOD RECORD 



April 25, 1922 



YARD AND tCILN 



qA Section Intended to Promote Efficiency^ 

 and Economy in Lumber Drying ^ 



Contention Tliat Lumber Does Not Shrink in Drying 

 Shown to Be Fallacious 



I 



*By William Snaith 



The busy factory executive, aud those to whom the more impor- 

 tant functions of plant management have been delegated, very 

 often do not have the time, or the inclination, to closely study this 

 important subject, which has all the appearance of complexity and 

 does, in fact, call for more than a little technical knowledge. It is, 

 however, based on a few broad fundamental principles, and it is 

 the purpose of this article to enunciate one of the principal of 

 these, which i;f rightly understood will prevent the executive from 

 being misled by statements and promises of fabulous savings. We 

 are inspired to write this by some statements we recently snw in 



From Circular 213, Forest Service, U. S. Department of Agricul- 

 ture, the following computations are made and quoted: 



LUMBER SHRINKAGE (PER CENT) GREEN TO OVEN-DKY 

 Species 



Regional 

 growth 



Basswood Pennsylvania . . . 



Basswood Wisconsin 



Beech Indiana 



Beech Pennsylvania ... 



Birch, yellow Wisconsin 



Birch, yellow Pennsylvania . . . 



Chestnut Tennessee 



Klin, cork Wisconsin 



71(4.3 



FDRfiT FROPOCTS EUGfNEERlMO Ca 



2 

 Z 



FtG. I. Two toards, A «n<5 », 

 cut from (Jlfferent sections of 

 tnc tree altho both are plain 

 aanm. Tangantlal direction. 



FIO. 2. Two boards, C .id P, 

 cut from different sao' lone of 

 the tree alche DotA are quarter 

 3a»n. Ra4lal dlreetton. 



Pt6. 3. Inilcatta "horn the board-A-wIll 

 Mt-vrai^y v^ry. 3hl& can be preventaa bv 

 proper treatment aLtho It Is phj-slcaUy 

 litiposBttle to pf«»e»rt: shrlntyage irtthmt 

 aertouR In^ry. 



These Sketches Explain the Directions of Shrinkage 



a circular which was intended to convey the impression that the 

 shrinkage of lumber could be entirely eliminated by some special 

 method, or methods, which the author of the circular had conceived. 

 Such statements fly directly in the face of natural physical laws. 

 The particular elementary principle which is violated by these 

 claims is the important fact which can be briefly stated thus — 

 lumber can not he expanded, in drying, but shrinks nearly in direct 

 proportion to the amount of moisture removed. This statement 

 holds true as long as it is understood that the lumber is not to be 

 injured. Of course, it is possible to reduce shrinkage by case- 

 hardening and honey-combing, but we do not suppose that the 

 author of the circular intended to advise the production of these 

 ill effects. 



Laws of Iiumber Shrinkage Known 

 The physical laws pertaining to the shrinkage of lumber through 

 extraction of moisture are just as surely known as the laws per- 

 taining to contraction and expansion of metal in varying tem- 

 peratures. 



• Secretary, Foreit Products Engineering Company, Republic Buitdrng, 

 Chicago. 



Gum, red 



Maple sugar Pennsylvania 



Maple sugar Indiana 



Maple, silver Wisconsin ... 



Oali, white swamp. Indiana 



Oak, white Louisiana .... 



Oak, white Arkansas .... 



Oak, red Tennessee ... 



Oak, white Indiana 



Oak, red Indiana 



In the foregoing table we have shown the various regional 

 growths in the sequence of increased shrinkage in volume of the 

 various species of the same group. For example, Indiana white 

 swamp oak shrinks the greatest amount in volume of any of the 

 other oaks shown. 



Directions of Shrinkage Shown 



An explanation of the two principal directions of shrinkage, tan- 

 gential and radial, is given in tha sketches shown above, the third, 

 longitudinal and negligible, as much so as thermal expansion and 

 contraction. 



It will be noted from the shrinkage table above that in the radial 

 direction very few of the species shown shrink more than 6 per 

 cent, only one being higher than 7 per cent. Furthermore, it must 



