March 10, 1917 



XiX 



The Conditions of Lumber 



By James E. Imrie 



Editor's Note 



This article deals with methods of measuring or testing conditions in seasoned lumber, its moisture distribu- 

 tion, shrinkage and easehardening, and was prepared in the Forest Products Laboratory at Madison, Wis. It fur- 

 nishes a number of practical hints tor those who want to examine lumber a little further than can be done by the 

 eye alone. 



In general, lumber should be seasoned with a definite use in view. 

 Frequently neglect of this simple practice is responsible for such 

 trouble as furniture and interior trim shrinking and checking, or wood 

 swelling out of shape when placed in a building. It is estimated that 

 the annual consumption of wood (excluding fuel and fencing) in the 

 United States, is approximately 52,000,000,000 feet board measure 

 If this tremendous supply of wood is to be marketed to the best ad- 

 vantage it should not only have certain properties for certain purposes 

 but should also be furnished in best condition for the purpose. 



So many questions concerning the conditions in lumber have been 

 submitted to the Forest Service, that it occurred to the writer to 

 suggest several simple methods of testing and measuring the conditions 

 in wood in order that manufacturers and users of lumber might de- 

 termine these conditions to their own satisfaction. This information 

 imay be obtained easily if the proper tests are applied. The purpose 

 •of this article is to explain how to make these tests in order that the 

 imoisture content, moisture distribution, shrhikage and easehardening in 

 tamber may be measured. 



Moisture Content 



The amount of water in lumber probably affects its adaptability 

 for a given use more than any other condition. Moisture content is the 

 determining factor affecting the use of lumber for articles to be exposed 

 to artificial heat, such as furniture and interior trim. This likewise 

 is true of all material to be subjected to natural heat, for example, 



structural timbers and all exterior work. The degree of dryness is 

 especially important for a vast number of special uses where strength, 

 hardness, shock-resisting ability, toughness, durability, and shrinkage 

 are vital factors, as in the manufacturing of vehicle wheels. If the 

 lumber is not very dry, shrinkage will occur causing the parts to be 

 loosely and insecurely assembled. If wood is to be bent, special eare 

 must be exercised to secure the proper moisture conditions. To enable 

 one to select lumber with the proper moisture content for these and 

 a multitude of other special uses, the following test wUl yield the 

 desired information. 



Test eor Moisture Content 



(Eefer to Fig. 1, moisture content.) Select several boards from 

 different portions of the pile and cut a section about an inch along the 

 grain from near the center of each. Sections cut less than one foot 

 from the ends of the boards are usually affected by end drying. First, 

 remove all splinters and loose particles from the outer surfaces and 

 label the sections so that they may be identified later. Weigh the 

 sections separately and to an accuracy of 1 per cent on a sensitive 

 balance and record the weights on the sections and on paper if a 

 permanent record is desired. The third- step is to place the sections on 

 hot steam pipes or in a drying oven heated to about 212 degrees 

 Fahrenheit. When they cease losing weight reweigh them to the same 

 accuracy. The first weight minus the second weight represents the 



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FIG. 1- METHODS Ol'' .MF.ASFRING AND DETERMINING CONDITIONS IN SEASONED LO.MliER 



—18- 



