No 



vember 



10, 1920 



Hardwood Record — Veneer & Panel Section 



When Lumber Is Ready to Be Taken from the Kiln 



The two things which a dry kiln operator must be able 

 to prove at the end of a kiln run are that his lumber is as 

 dry as is required and that it is free from invisible season- 

 ing stresses which would cause warping when the wood is 

 resawed and shaped into furniture or other products. 

 Neither of these points can be proved by examination of 

 the outside of the lumber. They are easily determined, 

 however, by the following tests which have been devised 

 by the U. S. Forest Products Laboratory, Madison, Wis- 

 consin : 



Before the lumber is removed from the kiln, choose a 

 fairly representative board from each truck load of stock. 

 Cut four 1 -inch cross-sections (A, B, C, D) from the 

 board at least 2 feet from the end. 



Use section A to find the average moisture content of 

 the dried stock. To do this, weigh the section immedi- 

 ately after cutting, on a balance accurate to 1 1 of 1 per 

 cent, and then dry it on a steam pipe or in an oven at 

 212 F. until it reaches constant weight. The weight lost 

 during this drying is the weight of the moisture which was 

 in the section. Divide the weight of the moisture by the 

 weight of the oven-dry section and multiply by 1 00. This 

 will give the percentage of moisture in the section and 

 also in the stock in that part of the kiln from which the 

 sample was taken. 



For furniture manufacture and other high grade uses, 

 the moisture content of any board in the kiln should not 

 vary by more than 2 or 3 per cent from the final moisture 

 content specified. 



Use section B to find out whether the stock is uni- 

 formly dry from center to outside. In order to do this 

 the section must be cut apart and the moisture content of 

 the inside and outside found separately. If the stock is 

 1 Yl inches or more in thickness, cut the section parallel 

 to its edges to get an outer shell of material V'-i inch thick. 

 Trim the remaining block equally on all four sides to leave 

 a core Yl inch thick. If the stock is less than 1 Yl inches 

 thick, cut section B so as to get an outer shell and inner 

 core each I '5 the total thickness of the section. Find 

 the moisture content of each piece by the method used 

 for finding the moisture content of section A. 



The moisture content of the inside and outside of the 

 stock should be equalized, by steaming if necessary, to 

 within 2 per cent before the lumber leaves the kiln. 



The third and fourth sections, C and D, are for case- 

 hardening and moisture distribution tests. Saw section 

 C parallel to the vk^ide faces of the original board to form 

 tongues or prongs, leaving about Yl inch of solid wood 

 at one end of the section. If the stock is less than 2 inches 



( t'diitii, m il I. II lutfif 42 ) 



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