6 BULLETIN 1060, IT. S. DEPARTMENT OF AGRICULTURE. 



sapwood. The longitudinal surface of the wood shows a silky sheen, 

 and the tangential surface, less noticeably, slight indentations or 

 dimples. There is no distinct line of demarkation between the spring- 

 wood and the summerwood as in Douglas fir. 



Compared with other woods of similar weight, Sitka spruce is of 

 greater strength and toughness. Table 17 (Appendix) shows the 

 value of its mechanical properties as measured by laboratory tests. 

 Individual test specimens may show a variation of as much as 16 per 

 cent from the data on bending, compression, shearing, tension, and 

 such properties. 



Spiral grain is found in Sitka spruce as in other species, though not 

 to any great extent. During the war specifications for airplane stock 

 required that no spiral-grained wood be accepted which had more 

 than 1 inch departure in 20 inches of length. Tests showed that a 

 greater amount of twist caused a marked reduction in strength for 

 aircraft purposes. Spiral grain in Sitka spruce can generally be 

 detected in the standing tree by a twisting of the fluted portions of 

 the lower trunk. 



The calorific power of one cord of air-dried Sitka spruce wood is 

 52 per cent of that of a short ton of coal, and that of western hemlock 

 and Douglas fir is 58 and 68 per cent, respectively. 



USES. 



The varied properties of Sitka spruce fit it for a wide variety of 

 uses. It is the premier wood for the manufacture of aircraft. It is 

 unsurpassed for pulp and is especially adapted for musical instru- 

 ments. It is also a desirable wood for boxes, crates, barrels, veneer, 

 and woodenware. 



By far the most extensive use to which the wood is put is the manu- 

 facture of lumber. As such, in one form or another, it is used for 

 about the same purposes as the other spruces. About 40 per cent is 

 used for construction and similar purposes without further manufac- 

 ture. While not suitable for heavy construction, it is well adapted for 

 many building uses in which light weight, ease in working, and 

 ability to take and hold nails and paints are essential. It is especially 

 suitable for large doors, such as are used for garages, freight houses, 

 and similar structures. It is extensively used for beveled siding. As 

 a car stock it is unsurpassed. The bulk of the lumber, however, is 

 remanuf actured into a large variety of products. 



More than half the lumber cut of this species is consumed by the 

 planing mill, box, and crate industries. It cuts to advantage for 

 doors, window and door frames, and molding. Belonging to the 

 class of tasteless woods, Sitka spruce is extensively used for contain- 

 ers in which articles of food are packed or handled. 



