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WOOD 280 – Macroscopic wood anatomy features

Grain

Figure

Knots

(Hoadley)(CMSA)

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"GRAIN" 1. Planes end, longitudinal, tangential, radial

2. Growth ring placement edge, quarter, vertical flat, mixed

3. Growth ring width fine, coarse, narrow

4. EW/LW contrast even, uneven

5. Alignment of straight, spiral, wavy longitudinal cells interlocked, steep

6. Relative pore size coarse, open, fine

7. Figure type stripe, fidddleback, bird’s-eye, curly

8. Machining defects chipped, fuzzy, raised

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Figure is broadly defined as any distinctive or characteristic marking on a longitudinal wood surface (T or R-plane). Wood without any visible characteristics is the exception rather than the rule. Microscopic changes can manifest themselves as macroscopic figure characteristics. In commercial terms, “figure” is generally reserved for the more decorative woods. Decorative figure is more frequent in hardwoods than in softwoods.

Figure in Wood

Curly Quilted Burl

(Hoadley)

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1. EW/LW differences

2. Pigmentation

3. Longitudinal parenchyma

4. RaysSilver grain ray flecks, slightly oblique to vertical axis (radial)Flake numerous short ray flecks (radial)Ripple marks storied cambium (tangential)

5. Deviation of longitudinal axis of cells from vertical axis.Crotch major branches (radial)Ribbon or stripe interlocking grain (radial)Fiddleback wavy grain (radial), regular changes in direction of grain in the

tangential directionRoe combination of interlocked grain and wavy grainBirds eye numerous, small indentations in the growth rings (tangential)Quilt indentations in cambium somewhat elongated transversely (tangential)Blister local irregularity in the growth rings (tangential)Burls irregular swellings of trunk caused by adventitious buds

Cause of Figure in Wood

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An example of a type of figure, how it is caused and how it is revealed

(Hoadley)

Burl

6http://www.cruisermotorsports.com/(CS)Honey%20Burl.gif http://images.meredith.com/wood/images/2008/01/p_figuringout1.jpg

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sitka spruce

Figure in softwoods

(Hoadley)

Vertical section through centre of tree

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KNOTS where the branches intersect the main stem. Always present so not of great importance when it comes to wood identification. Some species exhibit particular branching habits that can be used sometimes.

grain deviation

Knots

(Hoadley)

Examples of different appearance of knots

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Knot

Localized grain deviation around knot

The formation of live and dead knots

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The base of a growing branch, of which the growth increments are continuous with those of the trunk; this branch will give rise to a live, tight knot.

A branch has been cut (or broken off) and has died, so that the subsequent thickening of the parent trunk, its base, no longer growing will become enclosed in the growing trunk, giving rise to a dead or loose knot.

A branch has been cut off (pruned) flush with the trunk. Subsequent growth of the trunk produced knots-free (clear) timber.

A

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An intergrown knot is the base of a living branch within a tree. It is surrounded by a halo of circular growth rings. An intergrown knot is also called a "tight" knot because it is tightly bound to the wood around it.

An encased knot is formed when a tree grows around a dead branch. It is surrounded by a dark ring of bark, and its center is often decayed. An encased knot is also called a "loose" knot, because the bark prevents the knot from tightly binding to the wood around it.

Tight and loose knots

(CMSA)

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Loose knots

Loose knot Bark surrounding loose knot

The branches of some tree species are naturally more long-lived than those of other tree species. The longer lived branches will tend to give rise to larger knots. (This photograph was taken from the tree canopy walk at the UBC Botanical Gardens).

Self-pruning of trees