1. Wood consists of a multitude of cells, which differ from each other in shape, size, thickness of walls, contents, and arrangement. They are more or less firmly grown together. These cells may be as long as 1/3 inch in spruce or only 1/25 inch in some of the hardwoods. Cells of this sort are called fibres, in the softwoods they conduct water longitudinally in the tree. Cells of another kind which have greater diameter are called vessels; we can see them in the hardwoods. In the cells that make up wood rays water or sap is conducted in a radial direction.
2. No two woods have identical structure. The firs, pines, cedars, spruces and other needle-leaved softwoods have relatively few kinds of cells, while the hardwoods, such as oaks, beeches and maples have many kinds. These cells have various functions, such as conducting water, storing materials and reinforcing the structure.
3. The differences in cell structure produce a distinct pattern within the wood. This pattern becomes characteristic for each kind of wood, but it is never identical in any two pieces of the same wood. The grain figure is affected by the way the log is sawed. The woods that have considerable difference between springwood and summerwood are called coarse-grained; when there is little contrast, they are called fine-grained.
4. Here are the main types of wood grain. Straight-grained wood has the fibres running in the same direction as the main axis of the tree. Interlocked grain, occurs when layers of the wood alternate in direction. Such wood is difficult to split or to plane; for example, mahogany and elm. Wavy grain is almost a regular pattern of waves in the grain. Curly grain is a grain pattern with a definite curly appearance.
5. The grain pattern about the knots is circular and is usually more varied in direction than wood above or below the knot.
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What are the main types of wood grain?
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