WOOD 280 – Macroscopic wood anatomy features

Grain Knots (CMSA) Figure (Hoadley) 1

"GRAIN"

1. 2. 3. 4. 5. 6. 7. 8. Planes Growth ring placement Growth ring width EW/LW contrast Alignment of longitudinal cells Relative pore size Figure type Machining defects

end

,

longitudinal, tangential, radial edge, quarter, vertical flat, mixed fine

,

coarse

,

narrow even

,

uneven straight, spiral, wavy interlocked, steep coarse

,

open

,

fine stripe

,

fidddleback, bird’s-eye, curly chipped

,

fuzzy

,

raised

2

Figure in Wood

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.

Curly Quilted Burl (Hoadley) 3

Cause of Figure in Wood

1.

EW/LW differences 2.

Pigmentation 3.

Longitudinal parenchyma 4.

Rays Silver grain Flake Ripple marks ray flecks, slightly oblique to vertical axis (radial) numerous short ray flecks (radial) storied cambium (tangential) 5.

Deviation of longitudinal axis of cells from vertical axis.

Crotch major branches (radial) Ribbon or stripe Fiddleback interlocking grain (radial) wavy grain (radial), regular changes in direction of grain in the Roe Birds eye Quilt Blister Burls tangential direction combination of interlocked grain and wavy grain numerous, small indentations in the growth rings (tangential) indentations in cambium somewhat elongated transversely (tangential) local irregularity in the growth rings (tangential) irregular swellings of trunk caused by adventitious buds 4

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

(Hoadley) 5

Burl http://www.cruisermotorsports.com/(CS)Honey%20Burl.gif

http://images.meredith.com/wood/images/2008/01/p_figuringout1.jpg

6

Figure in softwoods

sitka spruce

(Hoadley) 7

Vertical section through centre of tree

8

Knots

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. (Hoadley) grain deviation 9

Examples of different appearance of knots

10

Knot Localized grain deviation around knot 11

*

The formation of live and dead knots

A

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.

(Wilson and White) 12

Tight and loose knots

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. (CMSA) 13

Loose knots

Loose knot Bark surrounding loose knot 14

Self-pruning of trees

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).