Handlens examination

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A routine starting point in identifying a given piece of wood is to locate a tiny area of end-grain surface where the wood can be cut cleanly with a razor blade or equally sharp tool to expose longitudinal cells in cross-section. When the exposed surface is examined with a good quality 10 X magnifier or hand lens, it can immediately be identified as a hardwood (pores visible) or softwood (pores absent). In addition, placement of growth rings and rays indicates the orientation of radial and tangential planes in the wood.

In cases where pores (and in some cases conspicuous rays) give immediate indication that the unknown is a hardwood, the pore distribution and size range suggests whether the wood is ring-porous, semi-ring-porous or diffuse-porous. This process of examination and deduction continues until all features have been evaluated. In summary, among hardwoods, hand lens observation of transverse surfaces reveals the relative width and distinc-tiveness of rays, the size and distribution of pores, and characteristic patterns of parenchyma cells.

An acetate measuring gauge, which can be ordered from most forest products laboratories, is helpful in measuring features such as pore quantity and size. Careful evaluation of typical characteristics will usually suggest an identification, at least to the genus, for most temperate region hardwoods. However, it is routinely recommended to follow through with microscopic examination of thin sections to confirm

Table 2.1 Representative woods found in furniture

Common and systematic names related/similar species

Key identification features

Macroscopic

Average relative densitya

Microscopic

Typical strength propertied

CII CI- MoR MoE

Shrinkage

SH St

Oak — Quercus spp. — Red oaks

  • 1) Q. rubra — Northern red oak
  • 2) Q. falcata — Southern red oak
  • 3) Q. coccinea — Scarlet oak
  • 4) Q. kelloggii — Calif. Black oak
  • 5) Q. palustris — Pin oak
  • 6) Q. velutina — Black oak

Oak — Quercus spp. — White oaks

  • 1) Q. alba — White oak
  • 2) Q. prinus — Chestnut oak
  • 3) Q. lyrata — Overcup oak
  • 4) Q. robur — European oak
  • 5) Q. petraea — Sessile oak
  • 6) Q. stellata — Post oak

Chestnut — Castanea spp.

  • 1) C. dentata — American chestnut
  • 2) C. sativa — European sweet chestnut

Heartwood light brown, usually with flesh coloured cast. Ring porous. Up to four rows of large solitary pores in early-wood. Late-wood pores solitary in radial lines, few and distinct ('countable'). Tyloses absent or sparse in early-wood. Largest rays conspicuous; tallest less than 1 in. Late-wood pores are the most reliable method for separating red and white oaks

Heartwood light to dark brown to greyish brown. Ring porous. Up to four rows of large solitary pores in early-wood. Late-wood pores small, solitary or in multiples, in spreading radial arrangement, numerous and indistinct ('uncountable'), grading to invisibly small with lens. Tyloses abundant. Largest rays conspicuous; tallest greater than 1.25 in

Heartwood greyish brown or medium to dark brown. Ring porous. Early-wood pores several pores wide; pores oval, surrounded by lighter tissue. Late-wood pores very numerous in radial dendritic or wandering patches. Tyloses present. Rays barely visible with lens

Narrow rays, uniseriate or in part biseriate. Late-wood vessels thick-walled

Narrow rays, uniseriate or in part biseriate. Late-wood vessels thin-walled

Rays almost exclusively uniseriate

(2) 0.54

  1. 6 8.61 98.5 12 500 42.0 7.44 75.1 10 300
  2. 9 7.92 95.8 11 300
  3. 6 4.0 11.3 4.7

11.1 4.4

  1. 3 7.37 105 12 300
  2. 5 12.1 90.9 10 400
  3. 7 5.24 59.3 8480
  4. 5 5.6 12.7 5.3

Elm — Ulmus spp.

  • 1) U. rubra — Slippery elm
  • 2) U. americana — American elm
  • 3) U. procera — English elm
  • 4) U. glabra — Wych elm
  • 5) U. alata — Winged elm

Heartwood light brown to brown or reddish brown, except (1) red to dark brown or reddish brown. Ring porous. Early-wood varies with species: (1) 2—6 pores, (2) fairly continuous row of large, uniformly sized evenly spaced early-wood pores, (3) and (4) similar, (5) early-wood pores small and indistinct in intermittent row. Late-wood pores in wavy bands.

homocellular, 1—7 (2) 0.50

  • mostly 4—5), seriate. (3) 0.49
  • 2,3,4) Rays (4) 0.60

homogeneous, 1—7 (5) 0.66 (mostly 4—6), seriate. (5) Rays homogeneous, 1—7,

Ash — Fraxinus spp.

  • 1) F. americana — White ash
  • 2) F. pennsylvanica — Green ash
  • 3) F. latifolia — Oregon ash
  • 4) F. excelsior — European ash
  • 5) F. nigra — Black ash

Walnut — Juglans spp.

  • 1) J. nigra — Black walnut
  • 2) J. regia — English walnut/ French walnut/Circassian walnut

Plane — Platanus spp.

  • 1) P. occidentalis — American sycamore
  • 2) P. acerifolia — London plane

Tyloses generally sparse in early-wood. Rays not distinct without lens. Heartwood of (1) fluoresces dim yellow-green

Heartwood colour light brown or greyish brown (1—4) greyish brown to medium or dark brown (5). Ring porous. Early-wood 2—4 pores wide, moderately large to large (5) surrounded by lighter tissue. Late-wood pores solitary and in radial multiples of 2—3 (not numerous in (5)). In (1—4), late-wood pores are surrounded by vasicentric parenchyma or connected by aliform parenchyma. In (5), aliform or confluent parenchyma in outer late-wood is rare. Tyloses fairly abundant. Rays not distinct to eye but clearly visible with hand lens.

(1): Heartwood medium brown to deep chocolate brown. Semi-ring porous. Early-wood pores fairly large, decreasing gradually to quite small in outer late-wood; pores solitary or in radial multiples of 2 to several. Tyloses moderately abundant. Short tangential lines of banded or diffuse in aggregates parenchyma visible with lens. Rays fine, visible but not conspicuous with lens. (2): very similar but appears lighter and less uniform in colour and more diffuse porous

Heartwood light to dark brown usually with a reddish cast. Diffuse porous; growth rings distinct due to unusual lighter colour of late-wood. Pores small, solitary, and in irregular multiples and clusters, numerous and evenly distributed throughout most of the growth ring. Late-wood zone evident by fewer, smaller pores and lighter colour. Rays easily visible without lens on all surfaces, appear uniform in size and spacing on transverse and tangential surfaces. Conspicuous dark ray fleck on radial surfaces

Rays 1—3 seriate. Late-wood pores thick-walled

51.1 9.71 106 12 200

Rays 1—5 seriate; ray cells appear round in tangential view. Crystals in longitudinal parenchyma and 'gash-like pits' in late-wood vessels occasionally found in (1) but not in (2)

Largest rays up to 14 seriate. Uniseriate rays not common

(2) 0.56

  1. 2 8.61 101 11 600
  2. 8 5.5 6.4 4.3

Common and systematic Key identification features

Average

Typical strength propertiesb

Shrinkage

names related/similar species

relative

(%)c

densitya

Macroscopic

Microscopic

C\\ Cl- MoR MoE SH

s, Sr

Beech — Fagus spp.

  • 1) F sylvatica — European beech
  • 2) F grandifolia — American beech

Maple — Acer spp. Hard maple group:

  • 1) A. saccharum — Sugar maple
  • 2) A. nigrum — Black maple
  • 3) A. pseudoplatanus — English sycamore

Soft maple group

  • 4) A. rubrum — red maple
  • 5) A. sacharinum — silver maple
  • 7) A. campestre — Field maple
  • 8) A. platanoides — Norway maple

Cherry — Prunus spp.

  • 1) P. serótina — black cherry
  • 2) P. avium — European cherry

Plums, peaches and apricots similar. Also in Rosaceae family, Malus (apple) spp. and Pyrus (pear) spp. — 'fruitwood'

Heartwood creamy white with reddish tinge to medium reddish brown. Diffuse porous; growth rings distinct. Pores small, solitary and in irregular multiples and clusters, numerous and evenly distributed throughout most of the ring; narrow but distinct late-wood in each ring due to fewer, smaller pores. Largest rays conspicuous on all surfaces; darker ray fleck against lighter background on radial surfaces

Heartwood creamy white to light reddish brown. Soft maples, red maple in particular may have an overall greyish cast or streaks. Diffuse porous. Growth rings are distinct due to narrow zone of darker brown cells at outer margin of growth ring. Pores small and solitary or in radial multiples of 2 to several — fairly uniform in size and quite uniform in distribution. Rays very distinct, the largest about as wide as the diameter of the largest pores. On radial surfaces, rays produce a conspicuous ray fleck -dark against lighter background

Light to dark cinnamon or reddish brown. Diffuse porous; growth rings sometimes distinct because of narrow zone or row of numerous slightly larger pores along initial early-wood. Pores through growth ring solitary and in radial or irregular multiples and small clusters. Gum defects common. Rays: not visible on tangential surface; conspicuous light ray fleck on radial surfaces; distinct bright lines across transverse surface, conspicuous with lens. Plums, peaches and apricots similar, apple and pear have narrower rays 1-3 (mostly 2) seriate

seriate; uniseriate (2) 0.64

rays common.

Occasional crystals in longitudinal parenchyma in (2)

5G,3 8,61 1G3 119GG

Fine, evenly spaced spiral thickenings. Simple perforation plates. Alternate, large intervessel pitting. In hard maples the largest rays are 7—8 seriate, and uniseriate rays are numerous. In soft maples, rays are 1—5 seriate

Hard

(5) G,47

  1. G 12.5 1G9 12 6GG
  2. 1 8.54 92.3 11 3GG

3—4) seriate. Spiral thickenings variable from thick to very thin, irregularly spaced (sparse in apple and pear).

Simple perforation plates. Alternate intervessel pitting.

Vessels with orange to ruby red contents

Birch — Betula spp.

  • 1) B. alleghaniensis — Yellow birch
  • 2) B. lenta — Sweet birch
  • 3) B. papyrifera — Paper birch
  • 4) B. pubescens — European birch
  • 5) B. pendula — European birch

Lime — Tilia spp.

  • 1) T. americana — Amer. basswood
  • 2) T. heterophylla — White basswood
  • 3) T. vulgaris — European lime

N. American cottonwood/poplar:

  • 1) P. balsamifera — Balsam poplar
  • 2) P. deltoides — Eastern cottonwood
  • 3) P. heterophylla — Swamp cottonwood
  • 4) P. trichocarpa — Black cottonwood

European poplars:

  • 5) P. alba — White poplar
  • 6) P. canescens — Grey poplar
  • 7) P. nigra — Black poplar

Aspens:

  • 8) P. grandidentata — Bigtooth aspen
  • 9) P. tremuloides — Quaking aspen
  • 10) P. tremula — European aspen

Heartwood light to dark brown or reddish brown. Diffuse porous. Growth rings may not be distinct — terminated by narrow zone of slightly denser, darker fibre mass. Pores small to medium, solitary or in radial multiples of 2 to several. With lens, pores clearly larger than width of rays. Some pores filled with whitish substance. Rays barely visible to unaided eye but distinct with lens on X section

Heartwood creamy white to pale brown. Faint but characteristic musty odour. Diffuse porous. Growth rings indistinct or faintly delineated by marginal parenchyma , sometimes with blurry whitish spots along the growth-ring boundary. Pores small, mostly in irregular multiples and clusters. Rays distinct but not conspicuous on transverse surface with lens

Heartwood in aspen typically light greyish brown. Cotton wood heartwood is greyish to light greyish brown, sometimes with an olive cast. In aspen, wood may be lustrous, cotton wood usually dull. Moist cottonwood has foul odour which disappears on drying. Growth rings distinct due to narrow margins of slightly darker denser fibres. Diffuse porous but larger, more numerous and crowded pores in early-wood grading to small in outer late-wood suggest a semi diffuse porous arrangement. Pores solitary and in radial multiples of 2 to several. In aspen, all pores are invisibly small. In cottonwood, the largest pores are usually barely visible to the unaided eye. Rays very fine, not easily seen with hand lens

spiral thickenings. (2) 0.65

Scalariform (3) 0.55

perforation plates (4) 0.59

with many fine bars. (5) 0.59 Intervessel pitting alternate, very small with confluent apertures

  1. 3 8.20 114 13 800 39.2 5.10 84.7 11 000
  2. 2 7.2 8.6 6.3

Rays 1—6 seriate. Ray

(1)

0.37

cells appear laterally

(3)

0.48

compressed in

tangential view. Rays

have bright yellow

cast. Thick, evenly

spaced spiral

thickenings. Simple

perforation plates.

Intervessel pitting

alternate

Rays uniseriate,

(1)

0.33

homocellular. Spiral

(2)

0.40

thickenings absent.

(4)

0.35

Perforation plates

(6)

0.40

simple. Intervessel

(8)

0.39

pitting, large

(9)

0.38

alternate

Common and systematic names related/similar species

Key identification features

Macroscopic

Average relative density

Microscopic

Typical strength propertied

CII CI- MoR MoE

Shrinkage

SH St

African mahogany — Khaya spp.

Central American mahogany • Swietenia spp.

Heartwood pale rosy red to dark reddish brown, often with purplish cast. Grain typically interlocked producing even stripe figure. Growth rings usually indistinct but sometimes distinct due to increased fibre density in outer late-wood or weakly defined terminal parenchyma. Diffuse porous. Pores medium to medium-large, visible without lens, relatively few to numerous, evenly distributed, solitary and in radial groups of 2—8. Some pores with red gum contents (but usually not white). Parenchyma usually not distinct without lens; terminal parenchyma occasionally present, poorly defined; vasicentric parenchyma narrow. Rays distinct on cross section without lens. On radial surfaces, ray fleck darker than background. Ripple marks usually not present, but if present are indistinct and irregular

Heartwood pale brown or pink to dark reddish brown. Grain straight or roey. Growth rings distinct due to concentric lines of terminal parenchyma easily visible without a lens. Diffuse porous. Pores medium-large, visible without lens, rather numerous, evenly distributed, solitary and in radial groups of 2—10. Some pores with red gum contents or whitish deposits. Parenchyma terminal and vasicentric. Rays barely visible without lens on cross section. On radial surfaces, ray fleck darker than background. Ripple marks usually distinct and regular; occasionally irregular, all elements storied

Rays of two sizes: smaller mostly 2—3 seriate, larger 4—7 seriate, with larger cells on flanks of rays (tangential view). Marginal cells and longitudinal parenchyma may contain crystals. Intervessel pitting alternate, very small

0.63

Rays 1—6 (mostly 3—4) seriate. Crystals in some marginal ray cells; longitudinal parenchyma occasionally contains crystals. Intervessel pitting alternate, very small

0.58

Teak — Tectona grandis

Heartwood dark golden yellow turning dark brown or nearly black with age. Waxy feel.

0.57

Straight grain. Characteristic spicy odour. Growth rings distinct, wood usually ring porous. Early-wood pores very large, solitary and in radial groups of 2—3; late-wood pores smaller, not numerous, evenly distributed; vessels with tyloses or with yellowish or whitish deposits. Parenchyma terminal and vasicentric. Rays distinct without lens on cross section

Rosewood — Dalbergia spp. Heartwood light to dark violet brown to D latifolia — Indian rosewood purple with near-black pigment layering that resembles growth rings. Grain irregular to roey. Growth rings indistinct. Diffuse porous. Pores variable in size, large to small, irregularly distributed, solitary and in radial multiples. Parenchyma aliform with short to very long wings; confluent forming wavy tangential bands; also apotracheal forming broken tangential lines or in smaller patches. Rays not visible without a lens. Ripple marks distinct and regular; all elements storied

Pine — Pinus spp. Hard pine group

  • 1) P. sylvestris — Scots pine
  • 2) P. resinosa — red pine
  • 3) P palustris — longleaf pine

Coniferous wood. Heartwood distinct, pale reddish-brown. Resinous odour. Wood medium texture, uneven grained (v. dense late-wood). Early-wood/late-wood transition abrupt, resin canals numerous, large, mostly solitary, evenly distributed

Larch — Larix spp.

  • 1) Z. laricina — Eastern larch
  • 2) Z. occidentalis — Western larch
  • 3) Z. decidua — European larch

Coniferous wood. Heartwood distinct yellowish to orange brown or russet (1) through to reddish brown (2) or brick red (3) in colour. Odourless. Uneven (1) to moderately uneven (2) grain. Early wood/late-wood transition abrupt. Rings in (2) generally narrow. Resin canals small, relatively few and variable in distribution, solitary or up to several in tangential groups. Texture medium-fine (1) to medium-coarse (2)

Heartwood light in colour; indistinct from sap wood. Odourless. Grain fairly even to longitudinal parenchyma with brown gum contents. Intervessel pitting alternate, medium

2—3) seriate; up to 15 cells high. Intervessel pitting alternate, medium-large

Epithelial cells thin- 0.46 - 0.60 walled. Rays heterocellular. Ray (1) 0.46

tracheids dentate. (2) 0.44 41.8 4.48 75.8 11 200 254 7.2 3.8 Crossfield pitting (3) 0.58 56.6 6.55 98.5 13 300 7.5 5.1

Epithelial cells thick- (1) 0.53 49.3 6.82 79.9 11 300

walled. Ray tracheids (2) 0.51 55.9 6.75 96.8 13 500 9.1 4.5

with Larix-type pits. (3) 0.53

Cross-field pitting piceoid. Longitudinal parenchyma absent

Epithelial cells thick- (1) 0.41 7.8 3.8

walled. Ray tracheids (2) 0.40 37.7 3.72 67.5 9 200

Common and systematic Key identification features

Average

Typical strength propertied

Shrinkage

names related/similar species

relative

(%)

density

Macroscopic

Microscopic

C\\ CI- MoR MoE SH

St Sr

  • 2) P. glauca — white spruce
  • 3) P. mariana — black spruce

Fir — Abies spp.

  • 1) A. balsamea — balsam fir
  • 2) A. concolor — white fir
  • 3) A. grandis — grand fir
  • 4) A. alba — Norway fir or silver fir moderately even. Early-wood/late-wood transition gradual. Resin canals small, relatively few and variable in distribution, solitary or up to several in tangential groups

Heartwood indistinct and light in colour. Odourless but may have bitter taste (2,3). Grain moderately uneven to moderately even. Early-wood/late-wood transition gradual (2—3) to very gradual (1). Resin canals absent. Texture medium (1) to medium-coarse or coarse (2,3). Norway fir is a low-density species similar to (1)

and II pits. Large bordered pits on radial walls of tracheids seldom paired. Longitudinal parenchyma absent

Cross-field pitting (1) 0.36

tracheids absent. Ray (3) 0.40

parenchyma end (4) 0.43

walls nodular.

Crystals sometimes present in ray parenchyma (2,3)

Longitudinal parenchyma usually absent. Rays in (4)

consistently exceed

30 cells in height

8470 9500

"Numbers in parentheses refer to named species in first column on left of table. The number sequence in this column is preserved in columns to the right so that, for example, in the shrinkage column values are given for Q. rubra, Q. falcata and Q. velutina but not for the other red oaks listed.

^Typical strength properties: Cll = compression parallel to grain MN/m2 maximum crushing strength. CI - = compression at right-angles to grain MN/m2 at proportional limit — when measuring compression perpendicular to grain, there is no meaningful maximum load — after reaching the proportional limit the piece is compacted more and more and resistance increases. MoR = modulus of rupture MN/m2. MoE = modulus of elasticity MN/m2. SH = side hardness kg.

cApproximate shrinkage as % of green dimension from green to oven-dry moisture content. St = tangential shrinkage; Sr = radial shrinkage.

Tracheid Pits Wood Anatomy Scots Pine

■ :. ■S® i:

ifi®

Figure 2.8 Photomicrographs of transverse (end-grain) sections of some types

of wood commonly found

in furniture.

A

northern red oak

Quercus rubra

H

American beech

Fagus grandifolia

Q

Central American mahogany Swietenia spp.

B

white oak

Quercus alba

J

sugar maple

Acer saccharum

R

teak

Tectona grandis

C

American chestnut

Castanea dentata

K

black cherry

Prunus serotina

S

Indian rosewood

Dalbergia latifolia

D

American elm

Ulmus americana

L

yellow birch

Betula alleghaniensis

T

eastern white pine

Pinus strobus

E

American white ash

Fraxinus americana

M

American basswood

Tilia americana

U

eastern Larch (tamarack)

Larix laricina

F

black walnut

Juglans nigra

N

quaking aspen

Populus tremuloides

V

eastern spruce

Picea spp.

G

sycamore

Platanus occidentalis

P

African mahogany

Khaya spp.

W

balsam fir

Abies balsamea

the analysis, or to make further separation to species, if indeed this is possible.

Table 2.1 gives data for selected woods representative of those commonly found in furniture. For each wood a general description is given, with principal identification features and summary data for physical and mechanical properties. Figure 2.8 shows cross-sectional views of the main genera represented in Table 2.1. These photographs enable a general comparison of representative types of hardwoods and softwoods. Macroscopic features that are useful for identification purposes can be observed. Further detailed information is given by Henderson (1960) and by Hoadley (1990).

With softwoods, hand lens identification is tentative at best, since for all conifers the bulk of the wood tissue consists mainly of tracheids. Some initial screening can be accomplished by determining the presence or absence of resin canals, the coarseness of texture, the uneven-ness of grain (texture) caused by early-wood/late-wood contrast, and whether the transition from early-wood to late-wood is gradual or abrupt. This information will lead to educated guesses, but conscientious identification of softwoods requires the microscopic evaluation of radial and tangential sections. Figure 2.8 T—W shows transverse surfaces of selected softwoods commonly found in furniture. For further information see Hoadley (1990).

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