Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.) 1. Wood (introduction...) 1.1. Structure of Wood 1.2. Chemical Composition of Wood (introduction...) 1.2.1. Cell Wall Components of Wood 1.2.2. Wood Constituents 1.3. Physical Properties of Wood (introduction...) 1.3.1 Wood Density 1.3.2. Moisture Content of Wood 1.3.3. Swelling and Shrinking of Wood 1.3.4. Thermal Properties of Wood 1.3.5. Acoustic and Electric Properties of Wood 1.3.6. Friction Properties of Wood 1.3.7. Strength of Wood 1.4. Important Wood Species 1.5. Wood Defects Caused by Growth Influences

Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.)

1. Wood

Wood is a tissue which is formed under the bark of the trunk by the meristem, the cambium. It consists of different cells.

1.1. Structure of Wood

The structure of the wood can be seen with the naked eye on the cut surfaces (see Fig. 1).

Figure 1 Sectional view

Fine Structure of Wood

The fine structure of wood is visible only under the microscope.

Tissue	Types of cells		Structure	Function	Occurrence
conducting tissue	tracheas		cells of different size and structure which are united into tubes; inside width: 0.02 - 0.5 mm length: a few cm to several m	water and nutrient conduction	deciduous wood
	tracheids		similar to the tracheas, but universally closed and dotted; inside width: 0.001 - 0.4 mm length: 0.3 -11 mm	water and nutrient conduction	all wood species
strengthening tissue and storage tissue	sclerenchymas		thick-walled, air-filled structures of small cross-section	strengthening of the wood	deciduous wood
storage tissue	parenchymas		mostly tape-shaped cells	metabolism and	all wood
		- axial parenchymas	strung together	storage of reserve substances	species
		- cross parenchymas	mostly square cells; containing many dots	nutrient storage and conduction in radial direction	all wood species
			longitudinal and cross parenchymae mostly form a multiple-branched network

1.2. Chemical Composition of Wood

Wood is composed of many chemical substances. The wood properties are considerably influenced by the composition.

Percentage in dry substance of wood

Carbon (C)	Oxygen (O)	Hydrogen (H)	Nitrogen (N)	Mineral substances
48...51	43...46	5...6	0.04...0.26	0.1...1.2

The percentages vary with the wood species.

1.2.1. Cell Wall Components of Wood

Percentage in dry substance of wood

Cellulose	Pantosanes	Lignin	Constituents
25...62	15.27	25...45	approx. 1.0
Composition of the cell components
44.4 % C	45.4 % C	62...69 % C	see under 1.2.2.
49.4 % O	49.4 % O	26...33.5 % O
6.2 % H	5.2 % H	6... 6.5 % H

1.2.2. Wood Constituents

Constituent	Description of the substance	Percentage in dry substance of wood	Importance of the constituent
alkaloids	metabolic product		protection against animal pests of wood
inorganic acid and salts	products of deposition		makes woodworking possibly more difficult
bitter substances	metabolic products
protein	ditto
colouring substances	excretion products of the cells or constituent of the cell sap
fats	reserve substances	up to 0.12...1.3 %
tannin	product of deposition	up to 17 %	protection against pests of wood, tannin extract recovery
glucosides	reserve substance
gum	protective substance		use for colouring and adhesive substances
resins	metabolic product		makes woodworking more difficult, serves for the manufacture of lacquers and adhesive substances
camphor	protective substance	up to 3 % and 1.5 % camphor oil	as distillation product for the recovery of essential oils
mineral substances	product of deposition		makes woodworking more difficult
oils	decomposition products	up to 1.6 %	protective agent
organic acids and salts	metabolic products		makes woodworking more difficult
odoriferous, toxic and curative substances	protective substance for the wood		may result in damage to the health during woodworking (see 1.4. under the various wood species)
starch	reserve substance	0.27...7.0 % sago palm up to 400 kg/tree	for food production and for gluten, thickeners and others
waxes	excretion products of the cell walls and the protoplasma	occurs seldom	makes surfaces treatment of the wood more difficult
sugar	conversion product of the starch	up to 3.5 % in the sap of Norway and sugar maple	saccharification of wood

1.3. Physical Properties of Wood

The physical properties of wood depend on the chemical composition and the biological structure.

1.3.1 Wood Density

The wood density is the ratio of the wood mass to the wood volume at a certain moisture content.

Designation	Definition	Calculation
density r	ratio of mass to volume of a substance	m = mass in g V = volume in cm
oven-dry density ro	density of absolutely dry wood	mo = mass in g at a moisture content of 0 % Vo = volume in cm3 at a moisture content of 0 %
gross density ru the following are usual:	density of wood at a specific moisture content	mu = mass in g at a specific moisture Vu = volume in cm3 at a specific moisture content
r 12...15 (12...15 % moisture content of wood) and r green (freshly felled timber)

Ratio of moisture content of wood to gross density (see Fig. 2).

Figure 2 Plot of gross density and moisture content

1.3.2. Moisture Content of Wood

The moisture of wood is the liquid content of wood.

Designation	Definition	Calculation
moisture content of wood u	water content of wood in % or in kg of water per kg of wood
oven-dryness	wood in absolutely dry condition
air-dryness	wood in air-dried condition (moisture content of wood 12 to 15 %)	u = moisture content of wood in % or in kg · kg-1 mu = mass of the damp wood sample in kg mo = mass of the oven-dry wood sample in kg
fibre saturation	cell walls completely saturated with water (moisture content of wood 22 ... 36 % depending on the wood species)
water saturation	all voids filled with water (maximum moisture content)

1.3.3. Swelling and Shrinking of Wood

Swelling and shrinking is the change of dimensions of wood as a result of moisture take-up by the incorporation of water into cell wall or by the extraction of water from the cell wall.

Behavior of the wood	Definition	Amount of the change in dimension	Schematic Representation
longitudinal swelling a1 and longitudinal shrinkage b1	change in dimension of the wood in grain direction as a result of take-up or liberation of water	0.05...0.07 %
radial swelling ar and radial shrinkage br	change in dimension of the wood vertically to the annual rings as a result of take-up or liberation of water	1.2...8.5 %
tangential swelling ar and tangential shrinkage bt	change in dimension of the wood in the direction of a tangent to the annual rings as a result of take-up or liberation of water	3.0...16.0 %

1.3.4. Thermal Properties of Wood

Wood has good heat-insulating properties, but is a bad heat conductor.

Quantity	Definition	Amount	Remarks
heat transfer coefficient a in kJ m-2 h-1 K-1	amount of heat which within a certain period of time is transferred at an interface from one material to another	for wood in calm air a = 20...32, in a breeze of 1...5 m s-1 a = 32...80
thermal resistance h in m2 h K kJ-1	resistance of a material to the heat transfer	d = wood thickness in mm l = coefficient of thermal conductivity in kJ m-1 h-1 k-1
flash point tF in ºC	temperature at which the wood starts to bum upon ignition	tF for wood 200...275 ºC
calorific value H in kJ kg-1	quantity of heat released during burning	calorific value for wood at uo H » 19000 kJ kg-1 at u = 12 % H » 13500 to 17000 kJ kg-1	H is increasing with the content of carbon, hydrogen, combustible constituents, lignin and with rising density

1.3.5. Acoustic and Electric Properties of Wood

The acoustic properties of wood result from its ability to vibrate.

The electric properties are based on the fact that wood acts as an insulator when oven-dry.

Quantity	Definition	Amount	Remarks
sound velocity C in m s-1	velocity at which sound waves propagate in a body	in grain direction 3000...5000 ms-1	the ratio of the sound velocity in wood in grain direction to that across the grain is 1.3...1.5
sound damping b in phones or decibels; sound absorption S in %	assimilation of sound energy by the body exposed to sound waves; ratio of the sound energy absorbed by a body to the sound energy arrived at the body	ks = absorbed sound energy ka = sound energy arrived
specific electrical resistance r in W cm	electrical resistance of a cube with an edge length of 1 m		is getting smaller with increasing density and moisture

Sound absorption S of some sound-absorbing materials in % at a frequency of 512 Hz

Material	Thickness in mm	Application	S in %
wood-wool boards	25	directly on the wall	35
wood particle boards	13	at a distance of 50 mm to the wall, surface untreated	19
felt	5	directly on the wall	18

1.3.6. Friction Properties of Wood

Friction is defined as the action of forces which at two contacting surfaces resist motion.

Quantity	Definition	Amount resp. Calculation
force of static friction FRmax in kp	force necessary to make two surfaces slide against each other	Frmax = f0 *FN fo = coefficient of static friction FN = normal force fo || » 0.6 fo ^ » 0.55
force of sliding friction FR in kp	force to overcome the resistance to motion when one surface is moving on other surface	FR = f * FN f = coefficient of sliding friction f || » 0.5 f ^ » 0.35
force of rolling friction FRmin in kp	force to overcome the resistance which counteracts the rolling off of a cylinder	F = force acting in the centre of the circle r = radius of the circle

1.3.7. Strength of Wood

Strength is defined as the resistance of a body put up to the indentation by another object.

Quantity Schematic representation	Definition	Amount
hardness H in MPa	resistance of a body to the action of external forces
compressive strength d dB in MPa	resistance of a body to a compressive force acting from outside	Fmax = compressive force Ao = cross-section
tensile strength d zB in MPa	maximum resistance of a body to tensile stress	Fmax = tensile force Ao = cross-section
bending strength 6 dB in MPa	maximum load occurring under a bending stress	Mbmax = bending moment W = moment of resistance
shear strength t aB in MPa	resistance to destruction by shearing forces	Fmax = shearing force Ao = shear surface
torsional strength t tB in MPa	highest tension occurring under torsional stress	Mt = torque a = length of a side of the cross-section

The torsional strength increases with density and with rising latewood and heartwood percentage and with decreasing moisture content.

Brinell hardness species in MPa of various wood			Mean shear strength of species in MPa various wood
Wood species	HB||	HB^	Wood species	t aB
Albura	48	28	Albura	7.6
Ailé	37	17	Ailé	7.0
Bété	85	33	Bété	8.0
Bossé	58	25	Bossé	10.6
Iroko	60	33	Ioroko	11.0
Tali	85	55	Tali	9.0

Calculation:

1.4. Important Wood Species

Trade name		Other names	Occurrence	Wood colour
				Heartwood	Sapwood
Abura		Bahia, Elilom, Subaha, Vuku	West and East Africa	greyish brown, brown to grey	yellowish red
African Mahogany		Khaya, Ndola, N’Gollom, Acajou d’Afrique	West Africa	light red, quickly darkening	light reddish grey
African Padouk		Barwood, Ndimbo, Epion, Takula, Ebeu	West Africa	coral-red, to reddish brown, darkening	whitish to cream-coloured
Aielé		Atué, Elimi, Abeui, M’bili, Bidinkala	West Central and East Africa	yellowish grey, yellowish brown	yellowish white to pale pink
Avodiré		Apaya, Engan, Agbé, Lusamba	tropic West Africa	pale yellow to cream-yellow, darkening
Bété		Aprono, Ofun, Mansonia	West Africa	brownish to olive, often darkening	whitish
Bilinga		Aloma, Badi, Kusia, Opepe, Akondoc	West and East Africa	salmon-coloured, rose-pink, darkening	pale pink
Bintangor		Koila, Calophyllum	South-East Asia	reddish brown	yellowish grey
Bossé		Divuiti, Ibotou, Ebang-bemva, Akuraten	West Africa	salmon-coloured, rose-pink, darkening	pale pink
Bubinga		Oveng, Okweni, Kevazingo, Essingang	West Africa	reddish brown to purple red veined	greyish white to pale yellow
Dabéma	Agboin, Atui, Toum, Dahoma, Bokundu		West and East Africa	yellowish brown to greyish brown		whitish grey to light brown
Dark red meranti	Adamui, Tanguile Nemesu, Meranti merah		South-East Asia	reddish brown		yellowish grey
Dibétou	Apop, Bibolo, Bombolu, Alop		tropic West Africa	light to dark brown darkening		pale yellow to pale brown
Douka	Okola, Bavili, N’duka		West Africa	light red to reddish brown		reddish white
Doussié	Afzelia, Bolengu, Papao, Uvala, M’bango		West and East Africa	light brown, often dark-veined		whitish to light yellow
Ebiara	Abem, Berlinia, Melegba, Obolo, Ekpogoi		West Africa	light reddish brown to reddish brown		yellowish white to reddish grey
Framiré	Lidia, Idigbo, Black afara		West Africa	greenish yellow, darkening		yellowish
Ilomba	Akomu, Lolako, Otie, Walélé		tropic West, Central and East Africa	pink to yellowish brown
Iroko	Abang, Odum, Kambala		West, Central and East Africa	greyish yellow to light brown, darkening		yellowish white to grey
Kosipo	Omu, Penkawa, Mpempe, Atomassié		West and Central Africa	reddish brown		grey
Krabak	Sanai, Ven ven, bac, Palosapis		South-East Asia	yellowish to yellowish brown, darkening		pale yellow
Limba	Afara, Akom, Fraké, Ofram		West and Central Africa	pale yellow with a touch of olive, also greenish grey
Makoré	Baku, Aganope, Butusu		West Africa	pink to reddish brown, darkening		cream-coloured to reddish darkening
Merawan	Thong, Koki, Thingan, Kien kien		South-East Asia	yellowish, quickly darkening		pale yellow
Moabi	Njabi, Adza, Dimpampi		West Africa	dark red to reddish brown, darkening		light pink to dark grey
Movingui	Eyen, Barré Ayan Bonsamdua		West Africa	lemon yellow to greenish yellow, darkening		yellowish grey
Mukulungu	Elang, Anzala, Fino, Autracon		West Africa	reddish brown, often dark-veined		yellowish grey to greyish brown
Naga	Okwen, Tebako, Meblo		West Africa	copper-coloured to reddish brown, light and dark stripes		light brown
Niangon	Ogoué, Kekosi, Yawi, Wishmore		West Africa	light to dark reddish brown, orange tinted		whitish to reddish grey
Okoumé	Caboon, Zonga, Angouma		West Africa	pale pink to reddish brown		light grey
East Indian jacaranda	East Indian rosewood, Sono keling, Eravadi		South Asia East India	yellowish brown to purple brown, darkening		yellowish
Ozigo	Assia		West Africa	grey yellowish to pale pink		pale grey, yellowish or reddish tinted
Sapelli	Lifaki, Sapele, Dilolo, Aboudikro		West, Central and East Africa	pale pink to light brown, darkening		cream-coloured, darkening
Sipo	Assié, Utile, Timbi, Ogipopo		West, Central and East Africa	reddish brown, darkening		reddish grey to light brown
Tali	Alui, Eloun, Erum, Kassa, Muave		West, Central and East Africa	yellowish to reddish brown, veined		greyish white to yellowish
Teak	Kyun, Giathi, Tek Sak		South and South-East Asia	golden to yellowish brown, partly veined		whitish to grey l
Tiama	Edinam, Kalungi, Timbi, Gedu nohor		West and Central Africa	light red to reddish brown, darkening		whitish to reddish grey
Wengé	Awong, Mboto, Nson-so		West Africa	light brown, veined, darkening		whitish to greyish white
Yang	Dau, Gurjun, Keruing, Dzao long		South and South-East Asia	greyish pink to reddish brown		greyish red
Zingana	Amouk, Zebrano, Izingana		West Africa	light brown to greyish brown, veined		whitish to grey

Trade name	Gross density r 12...15 in g · cm-3	Compressive strength d dB in MPa	Bending strength d bB in MPa	Tensile strength d zB in MPa
Abura	0.45 to 0.64	32...53	56...95	d zB^ 1.7...3.0
African Mahonany	0.45 to 0.62	36...58	36...126	d zB || 33...101 d zB ^ 1.7...2.3
African Padouk	0.65 to 0.85	65...81	110...149	d zB ^ 1.9...5.7
Ailé	0.36 to 0.57	33...49	27. ..84	d zB || 21...72 d zB ^ 1.6...2.6
Avodiré	0.50 to 0.60	40...57	52...113	d zB || 84...113 d zB ^ 2.1....2.9
Bété	0.58 to 0.68	48...97	62...187	d zB || 52...173 d zB ^ 4.5...7.4
Bilinga	0.70 to 0.90	47...73	85...130	d zB ^ » 2.2
Bintangor	0.48 to 0.66	43...60	48...107	d zB || 34...140
Bossé	0.55 to 0.65	45...61	74...110	d zB || 42...99 d zB ^ 2.0...2.4
Bubinga	0.80 to 0.95	65...76	125...160	d zB ^ 3.6...4.8
Dabema	0.65 to 0.80	47. ..75	75...125	d zB ^ 1.9...3.7
Dark red meranti	0.59 to 0.89	53...74	77...158	d zB || 66...222 d zB ^ » 2.7
Dibétou	0.43 to 0.65	33...47	56...89	d zB || 15...99 d zB ^ 1.6...2.1
Douka	0.65 to 0.75	40...71	41...146	d zB || 30...127 d zB ^ 1.9...2.3
Doussié	0.70 to 0.90	65...79	90...120	d zB ^ 1.8...2.3
Ebiaia	0.60 to 0.80	42...60	83...110	d zB ^ 2.7...4.0
Framiré	0.45 to 0.60	35...53	37...115	d zB ^ 1.2...2.3
Ilomba	0.35 to 0.53	31...45	41...74	d zB || 45...76 d zB ^ 1.7...2.9
Iroko	0.55 to 0.85	52...81	70...158	d zB || 55...140 d zB ^ 2.1...3.0
Kosipo	0.59 to 0.65	49...63	88...121	d zB || 32...155 d zB ^ 1.9...3.5
Krabak	0.64 to 0.69	40...69	72...132	d zB || 72...83 d zB ^ 3.8...5.6
Limba	0.48 to 0.78	35...48	58..94	d zB || 26...165 d zB ^ 1.5.-2.8
Makoré	0.53 to 0.72	40...71	41...146	d zB || 30...127 d zB ^ 1.9...2.3
Merawan	0.63 to 0.86	46...65	120...130	d zB ^ 2.4...3.0
Moabi	0.73 to 0.90	57...86	130...180	d zB ^ 3.2...4.4
Movingui	0.65 to 0.90	54...71	66...155	d zB || 27...96 d zB ^ 2.5...2.9
Mukulungu	0.78 to 1.04	73...107	100...178	d zB || 100...166
Naga	0.53 to 0.73	43...64	100...150
Niangon	0.58 to 0.72	56...68	87...140	d zB ^ 1.09...2.7
Okoumé	0.37 to 0.56	33...66	27...107	d zB || 23...125 d zB ^ 1.5...2.1
East Indian jacaranda	0.70 to 0.95	57...65	119...132	d zB ^ 3.4...6.5
Ozigo	0.50 to 0.75	58...71	110...130	d zB ^ 2.6...4.0
Sapelli	0.51 to 0.75	37...78	60...164	d zB || 53...154 d zB ^ 2.2....2.9
Sipo	0.55 to 0.75	43...73	47...155	d zB || 57...164 d zB ^ 2.0...2.6
Tali	0.85 to 1.07	75...86	120...150	d zB ^ 2.7...4.0
Teak	0.52 to 0.70	42...59	58...109	d zB || 95...155 d zB ^ 2.3...5.4
Tiama	0.51 to 0.63	38...59	61...92	d zB ^ 1.6...2.6
Wengé	0.75 to 0.95	68...90	115...170	d zB ^ 2.5...2.8
Yang	0.70 to 0.90	64...79	98...127	d zB || 97...127 d zB ^ 3.8...5.6
Zingana	0.70 to 0.85	35...66	84...120	d zB ^ 2.8...4.3

Trade name	General properties	Effects detrimental to health	Applications
Abura	moderately hard, well workable, well cleavable, can well be stained, dyed, varnished and impregnated; susceptible to wood pests, not weather-proof	causes occasionally dermatitis*)	for peeled veneers, doors, windows, interior work, for furniture and model making
African mahogany	well workable, can well be glued, stained and varnished, relatively resistant to wood pests, not weather-proof	causes dermatitis	for sliced veneers and peeled veneers, for furniture construction, interior work, for parquet, doors and windows
African Padouk	easily workable, can well be glued and especially well be varnished, resistant to wood pests and weather influence	causes dermatitis, grinding dust must well be sucked off	especially for sliced veneers, for building doors and windows, for parquet and furniture construction and interior work
Aielé	well cuttable, can well be nailed, screwed, glued, but is difficult to cleave; can well be stained and varnished; susceptible to wood pests, not weather-proof		for sliced and peeled veneers, in model making, for panelling and for packing
Avodiré	well cuttable and cleavable, can well be nailed, screwed and glued as well as stained and varnished, hard to impregnate, susceptible to wood pests, especially to blue stain, not weather-proof	causes occasionally irritations of the mucosa	preferably for making sliced veneer, but also for parquet, panelling and in furniture construction
Bété	well workable, tools quickly get dull, well cleavable, can be stained and varnished, susceptible to animal wood pests, resistant to plant wood pests, weather-proof	causes dermatitis and irritations of the mucosa, nausea, vertigo	especially for sliced veneer, for windows and doors, panelling, parquet, in furniture construction and interior work
Bilinga	well cuttable, tools quickly get dull, can well be glued, stained, but is difficult to varnish, resistant to wood pests and weather influences	wood dust causes dermatitis	for sliced veneers, for building windows and doors, furniture, panelling, parquet and for interior work
Bintangor	easily workable, tools quickly get dull, can well be nailed and screwed, hard to cleave, susceptible to wood pests, weather-proof	skin irritations and disturbances of the general state of health possible	for veneer and plywood production, for furniture construction, for panelling and parquet, in boat building
Bossé	well cuttable, tools quickly get dull, can well be glued and stained, but is difficult to varnish, resistant to wood pests and weather influences	wood dust causes dermatitis	for veneer production, in furniture production, for panelling and parquet, for building doors and windows
Bubinga	workable with difficulty, tools quickly get dull, hard to cleave, can well be glued, stained and varnished, resistant to wood pests and weather influences		for veneer production, for furniture construction, for parquet and panelling, in waggon and vehicle construction
Dabéma	workable with difficulty, tools quickly get dull, tends to splintering, predrilling is suitable for nailing and screwing, can well be stained and varnished, resistant to wood pests and weather influences	causes occasionally irritations of the mucosa	for manufacture of veneers, in furniture construction, for parquet and panelling, for interior work
Dark red meranti	easily workable, tools quickly get dull, can well be nailed and screwed, hard to cleave, susceptible to wood pests, weather-proof		for manufacture of veneers and plywood for furniture, parquet, windows and doors, for interior work and for boat building and vehicle construction
Dibétou	easily workable, predrilling required for nailing and screwing, can well be glued, stained and varnished, hard to impregnate, susceptible to wood pests, not weather-proof	causes occasionally dermatitis	for sliced veneer, for furniture construction, for panelling and parquet, for interior work, vehicle construction and boat building
Douka	well workable, predrilling required for nailing and screwing, can well be glued, stained and varnished, relatively resistant to wood pests and weather influences	causes dermatitis, irritations of the mucosa and conjunctiva	for manufacture of veneers, for windows and doors, interior work, for furniture, parquet, in ship building, waggon and vehicle construction
Doussié	well workable, tools quickly get dull, cannot be stained, hard to varnish, resistant to wood pests and weather influences	exposure to dust may result in irritations of the mucosa	for peeled veneer, windows, doors, floor coverings, furniture, in ship building and bridge construction, especially for laboratory furniture and containers for chemicals
Ebiara	well workable, danger of discolouring, can well be stained and varnished and easily impregnated, susceptible to wood pests, not weather-proof		for manufacture of sliced veneer, for internal work, in furniture construction and manufacture or parquet
Framiré	well cuttable and cleavable, can well be nailed, screwed, glued, stained and varnished, relatively resistant to wood pests, not weather-proof		for veneer and plywood production, for furniture, panelling, parquet, for windows and doors, interior work
Ilomba	can well be planed, milled, drilled, cleft, nailed, screwed, glued, stained and varnished, susceptible to wood pests, not weather-proof		for crossband veneers, packing and interior work, not suitable as building timber
Iroko	well workable, tools quickly get dull, predrilling required for nailing and screwing, can be varnished after pretreatment, cannot be impregnated, resistant to wood pests, weather-proof	causes occasionally dermatitis and irritations of the mucosa	for veneer and plywood production, for furniture, panelling, parquet, for doors and windows, for ship building and waggon construction and timber-work
Kosipo	well workable, tools quickly get dull, predrilling required for nailing and screwing, can well be glued, stained and varnished, susceptible to animal wood pests, not weather-proof		for sliced and peeled veneers, for plywood production, for furniture panelling and parquet and interior work
Krabak	well workable, tools quickly get dull, can well be nailed and screwed, glued, stained and varnished, susceptible to wood pests, not weather-proof		for veneer and plywood production, for furniture, parquet and interior work
Limba	well workable, can well be glued, stained and varnished, susceptible to wood pests, weather-proof	prolonged inflammations caused by splinter injuries are possible	for veneer and plywood production, interior work, for doors and windows, parquet, panelling, for furniture and timber-work
Makoré	well workable, tools quickly get dull, predrilling required for nailing and screwing, can well be glued, stained and varnished, relatively resistant to wood pests and weather influences	causes dermatitis, mucositis and conjunctivitis	for veneers, in furniture construction, for panelling, parquet, windows and doors, interior work, in ship building and waggon construction
Merawan	workable with difficulty, tools quickly get dull, can well be glued, stained and varnished, insect-proof, weather-proof, relatively acid-proof, durable under water		for sliced and peeled veneers, interior work, for floor coverings, panellings, in vehicle construction and ship building
Moabi	well cuttable, tools quickly get dull, can well be glued, stained and varnished, relatively resistant to wood pests, weather-proof	causes irritations of the mucosa	for veneer and plywood production, for furniture, parquet, windows and doors, interior work, vehicle construction, boat building and bridge construction
Movingui	workable with difficulty, tools quickly get dull, predrilling required for nailing and screwing, hard to cleave and glue, can well be stained and varnished, difficult to impregnate	causes occasionally dermatitis	for sliced veneeers, furniture, interior work, parquet, waggon construction, ship building and wood gluing work, for laboratory furniture and containers for chemicals
Mukulungu	well workable, tools quickly get dull, predrilling required for nailing and screwing, splinters, gluing difficult, paint coats badly adhere, hard to impregnate, acid-proof, resistant to wood pests and weather influences	causes irritations of the mucosa	for veneers, furniture, parquet, windows and doors, for interior work, waggon, vehicle and bridge construction, as timber for hydraulic engineering
Naga	well workable, predrilling required for nailing and screwing, can well be glued, stained and varnished, heartwood can be impregnated, relatively resistant to wood pests		for veneer and plywood production, for furniture and interior work, for windows, doors and floor coverings
Niangon	well workable, cleavable with difficulty, predrilling required for nailing and screwing, pretreatment necessary before gluing and surface treatment, resistant to wood pests, weather-proof		for veneer production, for interior work, for parquet, windows, doors, in vehicle construction, hydraulic and bridge engineering and construction of wooden houses
Okoumé	well workable, tools quickly get dull, can well be glued, stained and varnished, relatively resistant to wood pests, not weather-proof, fairly durable under water		for peeled veneer an plywood production, for furniture construction and interior work, for packing, in car body and boat building
East Indian jacaranda	well workable, tools quickly get dull, cleavable with difficulty, predrilling required for nailing and screwing, can well be glued, stained and varnished, resistant to wood pests, weather-proof	causes dermatitis	for sliced veneer production, for furniture, panelling, parquet, in model making and boat building
Ozigo	well workable, tools quickly get dull, can well be glued, stained and varnished, relatively resistant to wood pests, not weather-proof		for peeled veneer production, furniture construction, interior work, for parquet and packings
Sapelli	well workable, can well be glued, stained and varnished, relatively resistant to wood pests, not weather-proof		for sliced veneers, in furniture construction, for windows, doors, parquet, in vehicle construction and boat building
Sipo	well workable, can well be glued, stained and varnished, relatively resistant to wood pests, weatherproof		for veneer and plywood production, in furniture construction and interior work, for parquet, windows and doors, in vehicle construction and boat building
Tali	workable with difficulty, hard to cleave, tools quickly get dull, predrilling required for nailing and screwing, difficult to glue, can well be stained and varnished, resistant to wood pests, weatherproof	causes irritations of the mucosa	for veneer production, for parquet, windows, doors, floor coverings, in vehicle construction, bridge construction and mining, for containers for chemicals
Teak	well workable, predrilling required for nailing and screwing, tools quickly get dull, gluing and varnishing difficult, resistant to wood pests, weather-proof, acid-proof, inflammable with difficulty	causes occasionally dermatitis	for sliced veneers, in furniture construction, for parquet, windows, doors, for interior work, in vehicle construction and boat building, in hydraulic engineering, for containers for chemicals
Tiama	well workable, resin content causes clogging of the tools, can well be glued, stained and varnished, resistant to vegetable wood pests, but suscectible to animal wood pests, not weather-proof		for veneer and plywood production, for furniture, interior work, for parquet, windows, doors, in vehicle construction and boat building
Wengé	well workable, predrilling required for nailing and screwing, gluing and surface treatment difficult, resistant to wood pests, weather-proof		for sliced veneers, for furniture, panellings, parquet, windows and doors, as structural timber in the building industry
Yang	workable with difficulty, tools quickly get dull, resin content causes clogging of the tools, hard to glue, surface treatment difficult, relatively resistant to wood pests, moderately weather-proof	causes dermatitis, irritations of the mucosa furunculosis	for veneer and plywood production, for windows and doors, for interior work, vehicle construction and ship building
Zingana	moderately well workable, cleavable with difficulty, can well be glued, stained and varnished, resistant to wood pests and weather influences		for sliced veneers, in furniture construction, for interior furnishing, for windows and doors

*) dermatitis - inflammation of the skin caused by external influences

1.5. Wood Defects Caused by Growth Influences

Defects of and damage to the wood are deviations from the normal quality.

Kind of defect		Description of defect	Consequences	Wood species concerned
taper		reduction of the trunk diameter by 1 cm · m-1	lower wood yield	Douka, Yang
curvature		curved deviation of the trunk from the straight line	lower wood yield, warping, shakes	wood species mentioned under 1.4.
wavy rings	deviation from the normal trunk cross-section by pointed or round wave-shaped annual rings		limited use, lower wood yield, strength variations, warping, shakes	African Padouk, Avodiré, Tali
eccentric growth, heart displacement	deviations of the pith duct from the centre of the cross-section visible in the cross-section		limited use, lower wood yield, strength variations, warping, shakes	African mahogany, Ailé, Avodiré, Bété, Dark red meranti, Dibetou, Douka, Ebiara, Framiré, Ilomba, Kosipo, Limba, Krabak, Moabi, Mukulungu, Niangon, Okoumé, Ozigo Tali, Teak
spiral growth	helical wood fibre direction around the trunk axis		limited use, lower strength, shakes, warping	Abura
tension wood	wood zones on the upper side of crooked trunks and branches which appear to be of lighter colour than the surrounding wood		greater swelling and shrinkage, due to warping, shakes, working is more difficult	Doussié
ring shakes	circular shakes following the annual rings mainly in the lower part of the trunk		unusable as timber	African Padouk, Framieré
knottiness	excessive existence of a great number of knots, in particular also dry, dead knots		lower wood yield, lower quality of the timber, reduced strength	Abura, Avodiré, Bété, Dibetou, Framiré, Limba, Krabak, Mukulungu, Niangon, East Indian jacaranda. Teak, Wengé
shakes	separations of the fibre structure which may occur as radial and tangential shakes		limited use, lower wood yield, possibly not usable as timber	almost all wood species described under 1.4.
resin galls, resin pockets	narrow tangential clefts in the trunk which are of varying length and filled with resins or latex *)		working is made more difficult, limited use, lower wood yield, lower strength	Bitangor, Bubinga, Makoré, Tiama, Yang, Zingana
false heartwood, coloured heart-wood	differently coloured inner zone or the trunk depending on the wood species (brown, yellowish, green and other colours)		lower wood yield, limited use, lower quality of the final product	Tiama
figured growth burls	great nodular accumulation of a large number of dormant buds concentrated in a very confined space		low strength, working is made more difficult
blue stain and other discoloration caused by fungi	blue stain, but also fungus attack occuring as blue-green or brown discoloration of the wood, which may be accompanied by decay or insect damage		limited use, surface treatment made more difficult, reduced impregnability	Abura, African mahogany, Ailé, Avodiré, Bossé, Douka, Ebiara, Framiré, Ilomba, Krabak, Limba, Makoré, Movingui, Naga, Okoumé, Ozigo, Sapelli, Tiama

*) latex: rubber milk