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    Understanding Figure in Wood

    continued

    Bumps and Burls

    The cambium the layer between the bark and the wood sometimes has localized indentations, bumps, or bulges that leave behind wood of characteristic figure. In ponderosa pine, lodgepole pine, and Sitka spruce, dimpling sometimes occurs as numerous small, conical indentations of the plane of the growth ring. In occasional trees of sugar maple, localized small swirls of grain direction produce bird's-eye figure, so called because each swirl looks like a tiny eye.

    When finished smoothly, the variation in light reflectiveness because of grain distortion creates a very unusual three-dimensional effect, so that the figure seems to roll when the piece is moved. Quilted and blister figures are usually associated with bigleaf maple but are occasionally formed in other species as well.

    Burls are large, knoblike projections or bulges formed along the trunks (or sometimes limbs) of trees. The wood tissue within the burl is extremely disoriented and often contains numerous bud formations. The resulting figure is quite attractive and traditionally has been used in small articles such as bowls and turnings. Veneers cut from burls also display the fascinating figure.

    Figure also may be produced by irregular coloration. In hardwoods especially, the heartwood coloration is preferred and the sometimes lighter sapwood may be considered a defect and discarded. However, a striking effect in single and multiple pieces can be created by joining boards of such species as rosewood, black walnut, and eastern red cedar where sapwood is prominent.

    Within the heartwood alone, the term pigment figure refers to distinctive patterns formed by uneven extractive deposits. Some examples are rosewood, zebrawood, and figured sweet gum. It is interesting to note that the layering effect of pigmentation may be quite independent of the growth ring layering.

    R. Bruce Hoadley has a degree in forestry from the University of Connecticut and a doctorate in wood technology from Yale. He is professor of wood science and technology at the University of Massachusetts at Amherst. He frequently consults for museums and acts as an expert witness at trials.

    This article is excerpted from Understanding Wood: A Craftman's Guide to Wood Technology, copyright 2000, available from Taunton Press and at Amazon.com.

     

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    ArchWeek Image

    Ribbon or stripe figure in mahogany veneer. Varied vessel lengths and light reflection create the pattern.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    Broken-stripe figure in Ceylon satinwood, sometimes referred to as bee's-wing figure.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    Mottled figure occurs when the curly figure predominates in a piece with a combination of wavy and interlocked grain.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    Localized depressions in the growth rings, called dimples, are obvious on the split tangential surface of this piece of lodgepole pine.
    Photo: Randy O'Rourke

    ArchWeek Image

    Localized swirl in the grain of sugar maple produces bird's-eye figure.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    When the bulges of blister figure are elongated, quilted figure results. When smooth, the grain distortion creates an unusual three-dimensional effect that seems to roll when the piece is moved.
    Photo: Richard Starr

    ArchWeek Image

    A burl on a red oak stem. The wood tissue within a burl is distorted and often contains numerous bud formations.
    Photo: Randy O'Rourke

    ArchWeek Image

    Walnut burl figure is prized.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    Pigment-figured sweet gum.
    Photo: R. Bruce Hoadley

    ArchWeek Image

    Understanding Wood by R. Bruce Hoadley.
    Image: Taunton Press

     

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