There are five major spruces in North America, with three of them growing in the eastern half of the USA and Canada. These three, collectively called eastern spruce, are red spruce (Picea rubens), white spruce (P. glauca) and black spruce (P. mariana). Red spruce is found primarily in New England, the Appalachians and eastern Canada, while white and black spruce is found in the Great Lakes, New England and eastern Canada. The wood of these three spruces is impossible to separate visually once sawn into lumber. The properties of the three are also essentially identical.
Eastern spruce trees are usually not very large (seldom over 2 feet in diameter) and the lumber they produce often has many very small knots. The needles have been used for producing beer and tea. The roots were used by Native Americans for weaving baskets. The sap was reportedly used to develop chewing gum.
Spruce is known for its high strength compared to its weight. But the abundance of other softwood species with clearer wood in much of its growing area resulted in limited harvesting and manufacturing of eastern spruce lumber in the past. In Colonial times, the wood was used for mast and spars; this use continues today for small sailing boats. Eastern spruce has been used and still is used for piano sounding boards, violins and other musical instruments due to its excellent resonance properties. However, today, pulpwood is probably its number one use, followed by construction lumber, especially 2 x 4s and 2 x 6s, much of which is imported from Canada and is sold under the species grouping of SPF lumber (spruce, pine, fir). Yet this eastern spruce wood has potential for use in furniture and cabinets. Its gluing, machining, stability and strength properties are ideal for such uses. Perhaps the only limiting factor is, because of past history of usage and processing into construction lumber; that is, it is hard finding mills that will saw 4/4 and know how to properly dry such wood for furniture.
Processing suggestions and characteristics
Density. The three spruces have a density of approximately 27 pounds per cubic foot at 7 percent MC. This is one of the lightest-weight species in North America.
Drying. The spruces dry easily with few drying defects. If logs or green lumber are stored in warm weather, blue stain in the sapwood is common. Shrinkage in drying is 6 percent. Final moisture contents for the spruces should be between 7.5 to 9 percent MC. As with most softwood species, higher MCs are desired, because excessively dry wood will develop torn grain and may require increased glue spread to avoid a starved joint. On the other hand, wood much over 9 percent MC will shrink as it dries to its in-use MC and may develop some shrinkage defects.
Gluing and machining. The spruces machine very easily, with few defects except around the knots (typical cross-grain defects). Gluing is excellent. The softness means that the wood is quite forgiving if gluing conditions are not perfect.
Stability. The spruces are subject to minimal size changes when the MC changes — about 1 percent size change running across the grain parallel to the rings (tangentially) for each 5 percent MC change, and about 1 percent size change across the rings (radially) for each 10 percent MC change.
Strength. Spruces are medium in strength and stiffness. The bending strength (MOR) averages 10,800 psi for red and black and a little lower for white. Hardness averages 500 pounds. Stiffness (MOE) averages 1.6 million psi in red and black, with white being 1.43 million psi.
Color and grain. The grain of the spruces is straight, fine and uniform in texture. The wood is pale white in color, with the sapwood and heartwood being indistinguishable most of the time. The wood has no appreciable odor when dry.
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