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Red balau

Scientific name

Shorea principally S. kunstleri, S. guiso, S. collina, S. ochrophloia. Family: Dipterocarpaceae

Other names

Red selangan; urat mata; seangan merah (Sabah, Sarawak); bangkiri (Borneo); chan (Thailand); guijo (Philippines); giso; membatu (Indonesia)

The name balau is also used for some species of Hopea.

Description

  • Medium to large hardwoods.
  • Often buttressed.
  • Straight cylindrical bole 30–50m long.

Occurrence

Shorea spp. grow across:

  • Indonesia
  • Malaysia
  • Thailand
  • Philippines.

Appearance

Colour

  • Heartwood is red-brown to purple-brown.
  • Sapwood is distinctly paler.

Grain

  • Grain varies from straight to interlocked.
  • Interlocking grain produces striped figure (pattern) on quarter-sawn timber.
  • Texture moderately coarse but even.

Uses

  • Engineering: heavy engineering.
  • Construction: framing, flooring, linings, joinery, fencing.
  • Decorative: turnery.
  • Others: boat building, vats, casks.

Properties

  • Density: 840kg/m3 at 12% moisture content; about 1.2m3 of seasoned, sawn timber per tonne.
  • Strength groups: S3 unseasoned, SD4 seasoned.
  • Stress grades: F8, F11, F14, F17 (unseasoned); F11, F14, F17, F22 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: JD2 seasoned.
  • Shrinkage to 12% MC: shrinkage rates vary considerably between species.
  • Unit shrinkage: not available.
  • Durability above-ground: Class 4 (life expectancy less than 7 years).
  • Durability in-ground: Class 4 (life expectancy less than 5 years).
  • Lyctine susceptibility: untreated sapwood is susceptible to lyctine borer attack.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily accepts preservative impregnation.
  • Seasoning: be careful when drying to avoid splits, checks and distortion.
  • Hardness: hard (rated 2 on a 6-class scale) to indent and work with hand tools.
  • Machining: resinous material gums up cutting edges, otherwise relatively easy to machine and turn.
  • Fixing: pre-bore when nailing.
  • Gluing: as with most high-density species, machine and prepare surface immediately before gluing.
  • Finishing: satisfactory to paint, stain and polish.

Identification features

General characteristics

  • Sapwood: well defined and paler than heartwood.
  • Heartwood: purple-red or dark red-brown.
  • Texture: moderately coarse, even, interlocked grain; hard to cut across end grain; end cut is generally shiny with a degree of lustre on a dressed surface.

Wood structure

  • Vessels: mostly solitary with a few radial or oblique groups, medium size, even and diffuse distribution; tyloses are numerous; vessel lines present.
  • Parenchyma (soft tissue): apotracheal—consists mainly of irregular spaced bands and occasional short tangential lines or diffuse strands; paratracheal—often as incomplete vasicentric strands around the vessels, barely visible by hand lens, scant to well-defined aliform.
  • Rays: fine, generally inconspicuous on the radial surface.

Other features

  • Burning splinter test: match-size splinter burns to a charcoal.
  • Intercellular canals: generally filled with white resin, smaller than the vessels, and arranged in concentric formation.

Research and resources

  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • Queensland Government, DAF 2018, Construction timbers in Queensland: Properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.