DENSITY
The timber is a Heavy Hardwood with a density of 850-1,155 kg/m3 air dry.
NATURAL DURABILITY
The heartwood of this timber is naturally durable, but the sapwood is liable to fungal infestation. Under graveyard testing, untreated
specimens (50 mm x 50 mm x 600 mm) of balaukumushitam (S.maxwelliana) gave a life-span of 15.8 years, which made it one of the most durable timber tested in
Peninsular Malaysia (Jackson, 1965).Other test results recorded by Jackson include S.laevis (8 years) and S. glauca (7 years). In a later series of tests,
Dahlan& Tam (in press) reported that S.laevis lasted 7.4 years, thus confirming the results obtained by Jackson. Balau is thus placed in the durable class
with some species classified as extremely durable. Treated specimens of balaulaut (50 mm x 50 mm x 600 mm) gave an average service life of 11 years. Untreated
railway sleepers (125 mm x 237 mm x 1,950 mm) of balaukumus and balaulaut lasted a minimum of 15 years and 11 years respectively.
PRESERVATIVE TREATMENT
The timber is extremely resistant to treatment with preservatives.
TEXTURE
Texture is fine and even, with deeply interlocked grain.
STRENGTH PROPERTIES
The timber falls into Strength Group A (Engku, 1988b) or SG 1 (MS 544:Part 2:2001).
Strength Properties of Balau
| Species |
Test Condition |
Modulus of Elasticity (Mpa) |
Modulus of Rupture(MPa) |
Compression parallel to grain (MPa) |
Compression perpendicular to grain (MPa) |
Shear strength(MPa) |
| S.Glauca |
Green |
19,400 |
115 |
60.3 |
7.52 |
12.1 |
| S.Laevis |
Green |
18,400 |
121 |
68.8 |
9.52 |
12.9 |
| Air dry |
20,100 |
142 |
76.0 |
9.79 |
15.0 |
| S.Maxwelliana |
Green |
22,100 |
125 |
70.6 |
12.62 |
11.5 |
MACHINING PROPERTIES
It is moderately easy to difficult to resaw and easy to difficult to cross-cut. Planing is easy to difficult and the planed surface is
smooth to moderately smooth
Machining Properties of Balau
|
Condition |
Resawing |
Cross Cutting |
Ease of planing |
Quality of finish |
Ease of boring |
Quality of finish |
Ease of Turning |
Quality of finish |
| S.Glauca |
Green |
Moderately Easy |
Slightly difficult |
Moderately Easy |
Smooth |
Easy |
Smooth |
- |
- |
| Air dry |
Slightly difficult |
Difficult |
Slightly difficult |
Moderately Smooth |
Slightly difficult |
Smooth |
Easy |
Smooth |
| S.Laevis |
Slightly difficult |
Moderately Easy |
Easy |
Easy |
Smooth |
Easy |
Smooth |
- |
- |
| Air dry |
Slightly difficult |
Difficult |
Slightly difficult |
Moderately Smooth |
Slightly difficult |
Smooth |
Easy |
Smooth |
| S.Maxwelliana |
Green |
Slightly difficult |
Slightly difficult |
Slightly difficult |
Smooth |
Easy |
Smooth |
- |
- |
| Air dry |
Difficult |
Difficult |
Difficult |
Smooth |
Slightly difficult |
Smooth |
Easy |
Smooth |
Nailing Property
Nailing property is rated as very poor..
Air drying
The timber seasons very slowly, with severe end-checking and splitting, moderate surface-checking and staining as the main sources of defects.
13 mm thick boards take 4 months to air dry, while 38 mm thick boards take 8-10 months..
Kiln drying
Kiln Schedule B is recommended.
Kiln Schedule B
| Moisture Content(%) |
Temperature (Dry Bulb) |
Temperature (Wet Bulb) |
Relative Humidity (%)(approx.) |
|
F
|
F
|
F
|
F
|
|
| Green |
105 |
40.5 |
99 |
37.0 |
80 |
| 40 |
105 |
40.5 |
99 |
37.0 |
80 |
| 30 |
105 |
43.5 |
102 |
39.0 |
75 |
| 25 |
115 |
46.0 |
105 |
40.5 |
70 |
| 20 |
130 |
54.5 |
115 |
46.0 |
60 |
| 15 |
140 |
60.0 |
118 |
47.5 |
50 |
SHRINKAGE
Shrinkage is high, with radial shrinkage averaging 1.8% and tangential shrinkage averaging 3.7%.
DEFECTS
The heartwood is very seldom attacked by boring insects, but the sapwood, however, is liable to infestation by powder-post beetles.
Spongy heart and compression failures are unusual except in large, somewhat overmature trees (Thomas, 1958). Occasionally, resin pockets filled with solidified
resin may be found. A tangential zone of abnormal tissue with abundant intercellular canals and extending longitudinally for considerable distances may also be found.
USES
The timber is suitable for all forms of heavy construction, marine construction, ship and boat building (keels, keelsons and framework),
piling, beams, columns (heavy duty), bridges, wharves, cooling tower (structural member), railway sleepers, vehicle bodies (framework and floor boards),
boat building, plywood, joinery, cabinet making, mallets, fender supports, door and window frames, staircase (carriage, newel and stringer), pallets
(heavy and permanent type), tool handles (impact), telegraphic and power transmission posts and cross arms, posts, joists, rafters, flooring (heavy traffic),
decking and heavy duty furniture.
REFERENCES
Dahlan b. Jantan& Tam, M. K. (in press) - Natural Durability of Some Malaysian Timbers by Stake Test. Malay. For.
Engku Abdul Rahman Chik. 1998b. Basic and Grade Stresses for Strength Groups of Malaysian Timbers. Malayan Forest Service Trade Leaflet No. 38.
The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 13 pp.
Jackson, W. F. 1965. The Durability of Malayan Timbers. Mal. For. Ser. Trade Leaflet No. 28.
Lopez, D. T. 1983. Malaysian Timbers - Balau. Malaysian Forest Service Trade Leaflet No. 78. The Malaysian Timber Industry Board and Forest Research
Institute Malaysia, Kuala Lumpur. 9 pp.
Menon, P. K. B. 1986. Uses of Some Malaysian Timbers. Revised by Lim, S. C. Timber Trade Leaflet No. 31. The Malaysian Timber Industry Board and Forest Research
Institute Malaysia, Kuala Lumpur. 48 pp.
MS 544:Part 2:2001. Code of Practice for the Structural Use of Timber: Permissible Stress Design of Solid Timber.
Thomas, A. V. 1958. Malayan Timbers - Chengal and Balau. Mal. For. Ser. Trade Leaflet No. 20 (2nd. printing).
Wong, T. M. 1982. A Dictionary of Malaysian Timbers. Revised by Lim, S. C. & Chung, R. C. K. Malayan Forest Records No. 30. Forest Research Institute Malaysia,
Kuala Lumpur. 201 pp.
