Wood terms beginning with:


Sap - The water in a tree which is rich in minerals and nutrients.

Sapwood - The new wood in a tree that lies between the bark and the heartwood. Sapwood is usually lighter in color, and becomes heartwood as the tree ages. Under most conditions the sapwood is more susceptible to decay than heartwood.

Saw kerf - (1) Grooves or notches made in cutting with a saw; (2) that portion of a log, timber, or other piece of wood removed by the saw in parting the material into two pieces.

Seasoning - The process of removing the moisture from green wood to improve its workability and stability. Also called "drying". See air dried, kiln-dried, and kiln.

Seasoning (Air-Dried) - Dried by exposure to air, usually in a yard, without artificial heat.

Seasoning (Kiln-Dried) - Dried in a kiln with the use of artificial heat.

Second growth - Timber that has grown after the removal, whether by cutting, fire, wind, or other agency, of all or a large part of the previous stand.

Selects - In softwood, lumber which has been graded strictly for its appearance. In hardwood, lumber which is one grade below first and second.

Shake - A separation along the grain, the greater part of which occurs between the rings of annual growth. Usually considered to have occurred in the standing tree or during felling rather than a product of drying (see “Wind Shake").

Shaving - A small wood particle of indefinite dimensions developed incidental to certain woodworking operations involving rotary cutterheads usually turning in the direction of the grain (such as lathe turning). This cutting action produces a thin chip of varying thickness, usually feathered along at least one edge and thick at another and generally curled.

Shear - A condition of stress or strain where parallel planes slide relative to one another.

Shipping-dry lumber - Lumber that is partially dried to prevent stains and mold in transit.

Shrinkage - The percentage reduction in size of wood when it goes from green to dry. Wood shrinks differently in all directions, and specific shrinkage values can be obtained from the Louisiana Forest Products Laboratory or from the Wood Handbook. The values listed represent general relationships. This measure can also be used to estimate swelling when moisture is added.

Volumetric % Tangential % Radial %
High: High shrinkage and swelling >17% >11% >8%
Medium: Average shrinkage 13% to 17% 9% to 11% 6% to 8%
Low: Minimal shrinkage and swelling 9% to 13% 5% to 9% 3% to 5%
Very low: Shrinkage and swelling are ideal <9% <5% <3%

Sidebend - A distortion of a board in which there is a deviation edgewise from a straight line from end to end of the board.

Side-grained wood - Another term for flat-grained or plain-sawn lumber.

Side lumber - A board from the outer portion of the log-ordinarily one produced when squaring off a log for a tie or timber.

Slab - In a sawmill operation, a slab is the piece of wood cut off a log that is round on one side and flat on the other. These are produced from the first cuts on logs and the edging of flitches. They can be used for firewood, siding, or can be processed into lumber if large enough. The term is also commonly used for a very thick flitch cut from the log for possible use as a bench, table-top or mantle.

Slash-grained wood - Another term for flat-grained or plain-sawn lumber.

Soft hardwoods - Hardwood species with an average specific gravity less than 0.50, such as cottonwoods, basswoods, or willows. See also "Hard Hardwoods".

Soft rot - A special type of decay developing under very wet conditions (as in cooling towers and boat timbers) in the outer wood layers, caused by cellulose-destroying microfungi that attack the secondary cell walls and not the intercellular layer.

Softwoods - Generally lumber from a conifer such as pine or cedar. The name softwood does not refer to the density or hardness of the wood. There are some hardwoods which are softer than some softwoods.

Sound - A term referring to a board which has no or very few defects which will effect its strength

Sound knot - A knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.

Spalting - A by-product of the rotting process that is carried out by a vast array of stain, mold and decay fungi, that are found naturally on the forest floor. When the temperature and humidity are right, spalting can cause many different and beautiful patterns in rotting wood. The unusual colouration may be due to chemically induced reactions between the wood, fungi and insect deposits, often resulting in black, pink, grey and multicoloured streaked wood. Spalting may also be induced in an unspalted piece of wood to enhance its beauty.

Species - A category of biological classification; a class of individuals having common attributes and designated by a common name. "Species" is always properly used with the "s" when referring to trees or other biological classifications.

Specific gravity - (1) The ratio of the weight of wood to an equal volume of water. The higher the specific gravity, the heavier the wood. (2) As applied to wood, the ratio of the ovendry weight of a sample to the weight of a volume of water equal to the volume of the sample at a specified moisture content (green, air-dry, or ovendry).

Spike knot - A knot cut approximately parallel to its long axis so that the exposed section is definitely elongated.

Spindle - A narrow, turned piece of wood.

Spiral-grained wood - Wood in which the fibers take a spiral course about the trunk of a tree instead of the normal vertical course. The spiral may extend in a right-handed or left-handed direction around the tree trunk. Spiral grain is a form of cross grain.

Split Resistance - A measures of how well the wood resists splitting from nailing. (Pilot holes can reduce the splitting.)

Poor: Splits very easily.
Fair: Somewhat easy to split.
Average: Average.
Fine: Somewhat difficult to split.
Excellent: Extremely difficult to split.

Stain - A discoloration in wood caused by a fungus, minerals or chemicals. A die or pigment used to discolor wood.

Blue stain - A bluish or grayish discoloration of the sapwood caused by the growth of certain dark-colored fungi on the surface and in the interior of the wood; made possible by the same conditions that favor the growth of other fungi.

Brown stain - A rich brown to deep chocolate-brown discoloration of the sapwood of some pines caused by a fungus that acts much like the blue-stain fungi.

Chemical brown stain - A chemical discoloration of wood, which sometimes occurs during the air-drying or kiln drying of several species, apparently caused by the concentration and modification of extractives.

Sticker stain - A brown or blue stain that develops in seasoned lumber where it has been in contact with the stickers.

Sticker - A ¾" to 1" wood strip that is inserted between stacks of green wood and spaced between 16" to 24" to allow air to flow through the stack to ensure proper drying.

Straight-grained wood - Wood in which the fibers run parallel to the axis of a piece.

Stump-Shot Lumber - Lumber having jagged or irregular ends, sawn from a butt log.

Surfaced lumber - A piece of wood that has been planed smooth on one or more surfaces.

Surfacing - The process of planing lumber at the lumber mill in order to smooth one or more surfaces.

The Wood Glossary

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