Seasoning of Wood. 



141 



tin- Shrinkage greatest 

 in the outer Wood. 



570. Seasoning tends to secure the durability of wood not ex- 

 posed to the weather, or in contact with the earth, or with damp 

 walls, if sufficient ventilation is allowed. The presence of moisture, 

 and especially of the starch, sugar, and albumen of the sap in wood, 

 tends to hasten fermentation and decay. If these are partly dis- 

 solved out by placing the freshly cut timber in running water, it 

 drys more readily. Seasoning by smoking has the effect of increas- 

 ing the durability of wood, by charging it with creosote, but this is 

 corrosive to iron, and should not be used in contact with it. 



571. In the process of seasoning, wood tends to shrink, from the 

 contraction of the tissues as they become dry. 



As there is more moisture and less wood lilirr 

 in the outer layers, the contraction is greatest 

 toward the outside, as shown in the annexed 

 engraving. The process takes place more 

 slowly, and with less cracking in winter. It is 

 still further improved by delaying the drying, 

 which may be done by placing in the shade, 

 where the air circulates freely between the 

 pieces, but it should not be exposed to the dry- 

 ing winds. 



">7L'. It is desirable to prevent the cracking of timber at the ends, 

 by which means a lo.-s is suffered in the more valuable kinds. This 

 may Iv prevented in a great degree, by pasting heavy paper over 

 the end. or by painting or washing with diluted muriatic acid, neu- 

 trali/.ed with lime. 



573. If there be nothing at hand better, the timbers may be lightly 

 shaded from the sun by branches of trees or 

 any other slight covering, where it i- desirable 

 to prevent deep crevices from being formed. 

 Shrinkage tends to distort timber that is dressed 

 green, as shown in the annexed cut, and un- 

 less the center of growth is in the center of 

 the piece, it will need to be dressed over again 

 to secure a true form. Boards and plank when 09 Tendency to Distor- 

 cut green will warp from this cause, the contrac- ^ 



tion being strongest on the side fur- 

 therest from the center of growth, and 

 least in the direction of the medul- 



1 70. Tendency to Warp by Contraction 



nil \ i ft\ *. nearest the Outside of the Tree. 



