I'- I / 
 
 TECHNICAL NOTE number 128 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE 
 
 FOREST PRODUCTS LABORATORY 
 
 madison 5. Wisconsin / "»'^n June 1953 
 
 „ UNIV. OF FL MR "~ 
 
 DOCUMH^ JM ' l_lib T ' 
 
 MOISTURE CONTENT AND STORAGE AF'FKCT; 
 STRENGTH OF NAILED foOQD BOXES 
 
 u.s. Depository 
 
 Of two boxes made exactly alike from the same grade and thickness of 
 lumber, one may stand ten times as much rough handling as the other, 
 because of a difference in the moisture content of the lumber or a differ- 
 ence in subsequent storage conditions. Tests made at the Forest Prod- 
 ucts Laboratory, Madison, Wis. , show that only when a box is to be 
 used for an extremely short time immediately after manufacture is the 
 proper seasoning of the lumber unimportant. 
 
 Within a week after manufacture a box made of green lumber suffers a 
 marked reduction in strength. As the wood dries, the nails lose their 
 grip. The fibers which are bent down along the nail shrink away from 
 it in the direction of the end grain, the direction in which it was most 
 firmly held, leaving the nail held only by two sides. Under suchcircum- 
 'stancesthe weaving action during transportation alone will readily cause 
 the nails to work loose and even come out of the box. Boxes made of 
 greenlumber at the Laboratory and kept for a year indry storage tested 
 only about one-sixth as strong as similarly-made boxes tested at the 
 time of manufacture. 
 
 If a box is made of dry wood and then subjected to alternate wettings and 
 dryings, through cold storage or exposure to weather, the nails will be 
 loosened just the same as in green lumber. Boxes made up from dry 
 lumber were kept for two weeks in damp storage and then for two weeks 
 in dry storage. After this treatment the boxes withstood only one-tenth 
 as much rough handling as those made of air-dry lumber which had not 
 been subjected to adverse storage conditions. 
 
 A box made of lumber in the proper moisture condition will stand ordi- 
 nary storage without any appreciable loss in the holding power of the 
 nails. The best results are, therefore, obtained when the lumber is 
 seasoned in accordance with the atmospheric conditions which the box 
 will encounter in service. If it is impossible to forecast thci>e condi- 
 tions, it is advisable to use thoroughly air-dry lumber, which contains 
 from 12 to 18 percent moisture. 
 
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UNIVERSITY OF FLORIDA 
 
 3 1262 09216 7070