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Tallowwood

Scientific name

Eucalyptus microcorys. Family: Myrtaceae

Description

  • Moderate to large tree.
  • Grows to 25–60m high.
  • Stem grows 1–2m diameter.
  • Form is generally good with a straight, clear bole (trunk) to two-thirds of the total height.
  • Bark is soft, flaky, fibrous and persistent (doesn’t shed) up to the small branches.
  • Bark is brown to yellow-brown.
  • Bark often has surface pores and horizontal cracks on under layers, and a characteristic spongy response to finger pressure.

Occurrence

  • Found in coastal wet sclerophyll forests from Newcastle, New South Wales to Maryborough and Fraser Island, Queensland.

Appearance

Colour

  • Heartwood is pale to dark yellow-brown.
  • Sapwood is usually almost white.

Grain

  • Texture is moderately coarse, generally with interlocked grain.
  • Usually free from gum veins.

Uses

  • Engineering: sawn and round timber to construct wharves and bridges, railway sleepers, cross arms, poles, piles, mining timbers.
  • Construction: unseasoned timber in general house framing, and dressed timber in cladding, internal and external flooring, linings and joinery; also fencing, landscaping, and retaining walls.
  • Decorative: outdoor furniture, turnery, joinery.
  • Others: structural plywood, boat building (keel and framing components, planking), coach, vehicle and carriage building, agricultural machinery; used, in the past, for bearings, mallet heads, mauls, wheel spokes, cooling tower components, tool handles, croquet mallets.

Properties

  • Density: 1010kg/m3 at 12% moisture content; about 1.0m3 of seasoned sawn timber per tonne.
  • Strength groups: S2 unseasoned, SD2 seasoned.
  • Stress grades: F11, F14, F17, F22 (unseasoned); F17, F22, F27, F34 (seasoned) when visually stress-graded according to AS 2082—2000, Timber—Hardwood—Visually stress-graded hardwood for structural purposes.
  • Joint groups: J1 unseasoned, JD1 seasoned.
  • Shrinkage to 12% MC: 6.1% (tangential), 3.7% (radial).
  • Unit shrinkage: 0.37% (tangential), 0.28% (radial)—these values apply to timber reconditioned after seasoning.
  • Durability above-ground: Class 1 (life expectancy more than 40 years).
  • Durability in-ground: Class 1 (life expectancy more than 25 years).
  • Lyctine susceptibility: untreated sapwood susceptible to lyctid borer attack.
  • Termite resistance: resistant.
  • Preservation: sapwood readily impregnates with preservative,  but penetration of heartwood is negligible using available commercial processes.
  • Seasoning: satisfactorily dries using conventional air and kiln seasoning.
  • Hardness: very hard (rated 1 on a 6-class scale) to indent; relatively easy to work with hand tools due to its natural greasiness, and hence the descriptive name given to the timber by early settlers.
  • Machining: machines and turns well.
  • Fixing: no difficulty using standard fittings and fastenings.
  • Gluing. As unseasoned timber in general house framing and as seasoned dressed timber in cladding, internal and external flooring, linings and joinery. Also in fencing, landscaping and retaining walls.
  • Finishing: readily accepts paint, stain and polish.

Identification features

General characteristics

  • Sapwood: pale, almost white.
  • Heartwood: varies from light to dark yellow-brown.
  • Texture: moderately coarse, generally with interlocked grain; greasy to touch.

Wood structure

  • Growth rings: absent.
  • Vessels: medium, solitary with some touching; a few in multiples, often oblique chains; abundant tyloses; prominent vessel lines.
  • Parenchyma: visible with the aid of a lens; abundant, paratracheal and diffuse.
  • Rays: fine.

Other features

  • Burning splinter test: produces a charcoal tipped with grey or white ash.
  • Figure (pattern): lacking, but has distinctive lustre and appears greasy.

Research and resources

  • Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, Forest trees of Australia, 5th ed., CSIRO Publishing, Collingwood, Australia.
  • 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.