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Rubberwood

Scientific name

Hevea brasiliensis. Family: Euphorbiaceae

Other names

Para rubber tree

Description

  • In nature, rubberwood is a large hardwood.
  • In plantations, at the time of felling (usually 25 years) trees have a clear bole (trunk) more than 10m high and 25–45cm in diameter.

Occurrence

  • Occurs in tropical evergreen rainforests of:
    • Brazil
    • Bolivia
    • Guianas.
  • Planted extensively in many tropical countries to produce latex (natural rubber).
  • Mostly produced in:
    • Indonesia
    • Malaysia—has 2 million hectares of rubber plantations and produces 45% of total world rubber.

Appearance

Colour

  • Sapwood is not distinct from the heartwood.
  • Timber is whitish yellow when freshly cut and seasons to cream, straw or light brown, often with a pinkish tinge.

Grain

  • Grain is straight to shallowly interlocked or wavy.
  • Texture is moderately coarse but even.

Uses

  • Construction: flooring, internal step treads, concrete formwork, joinery.
  • Decorative: panelling, balustrading, parquetry, joinery, turnery. Used extensively in the Australian furniture market as indoor furniture e.g. dining suites, bar stools and rocking chairs.
  • Others: particleboard, knife blocks, cheese boards, salad bowls, trays.

Properties

  • Density: 640kg/m3 at 12% moisture content; about 1.6 to 1.8m3 of seasoned sawn timber per tonne.
  • Strength groups: (S7) unseasoned, (SD7) seasoned (brackets indicate provisional value).
  • Stress grades: F4, F5, F7, (unseasoned); F5, F7, F8, F11 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood— Visually stress-graded for structural purposes.
  • Joint groups: JD3 seasoned.
  • Shrinkage to 12% MC: not available.
  • 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 susceptible to lyctid borer attack.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily impregnates with preservative, but penetration of heartwood is variable using available commercial processes.
  • Seasoning: seasons rapidly but prone to distort if not carefully stacked and dried; very stable in-service.
  • Hardness: firm (rated 4 on a 6-class scale) to indent and working with hand tools.
  • Machining: easy to saw, cross-cut, plane, turn and bore; maintain sharp cutting edges to avoid 'woolliness'.
  • Fixing: pre-bore prior to nailing.
  • Gluing: glues satisfactorily.
  • Finishing: readily accepts paint, stain and polish.

Identification features

General characteristics

  • Sapwood: not differentiated from the heartwood.
  • Heartwood: whitish yellow when freshly cut, darkening to cream-straw or light brown on exposure, often with pink tints.
  • Texture: moderately coarse but even.

Wood structure

  • Vessels: small to medium, generally arranged in short radial multiples with few solitary and occasional clusters; obvious vessel lines on longitudinal face.
  • Resin canals: numerous; prominent as lines on dressed longitudinal surfaces.
  • Parenchyma (soft tissue): distinct regularly spaced bands forming a net-like pattern with the rays.
  • Rays: fine to medium, readily visible with a lens.

Other features

  • Deposits: tyloses present.

Research and resources

  • Bootle, K 2005, Wood in Australia: Types, properties and uses, 2nd ed., McGraw-Hill, Sydney.
  • 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.