Kwila

Scientific name

Intsia bijuga (formerly Afzelia bijuga syn. Afzelia australis), I. palembanica. Family name: Leguminosae.

Local names

Johnstone River teak, scrub mahogany (North Queensland), merbau (Malaysia), vesi (Fiji), Moluccan ironwood (United Kingdom), go-nux (Vietnam), ipil (Philippines), hintzy (Madagascar), melila, bendora (Papua New Guinea), lumpho, lum-paw, makamong (Thailand), kivoli, vuvula (Solomon Islands).

Description and natural occurence

A large hardwood attaining 40 m in height, with a trunk of 0.6 m diameter. Often a bushy tree forming a spreading canopy.

Occurs in the Johnstone River and Daintree areas of North Queensland, Malaysia, Fiji, Vietnam, Philippines, Madagascar, Papua New Guinea, Thailand, Solomon Islands, New Caledonia, Vanuatu and Samoa.

Wood appearance

Colour. Heartwood yellowish-brown or orange-brown when first cut, turning darker with age to brown or deep reddish brown. Sapwood white, pale yellow or buff and sharply differentiated from heartwood.

Grain. Grain variable but usually interlocked or wavy, texture is coarse but even. Attractive figure on backsawn material.

Wood properties

Density. 830 kg/m3 at 12% moisture content; approximately 1.2 m3 of seasoned sawn timber per tonne.

Strength groups. S2 unseasoned; SD3 seasoned.

Stress grades. F11, F14, F17, F22, (unseasoned), F14, F17, F22, F27, (seasoned), when visually stress graded in accordance with AS 2082:2000, Timber - Hardwood - Visually stress-graded for structural purposes.

Joint groups. J3 unseasoned; JD2 seasoned.

Shrinkage to 12% MC. 2.6% (tangential); 1.2% (radial).

Unit shrinkage. 0.30% (tangential); 0.19% (radial). These figures apply to timber reconditioned after seasoning.

Durability above-ground. Class 1 - life expectancy over 40 years.

Durability in-ground. Class 3 - life expectancy 5 to 15 years.

Lyctine susceptibility. Untreated sapwood susceptible to lyctid borer attack.

Termite resistance. Resistant.

Preservation. Sapwood accepts preservative impregnation.

Seasoning. Kwila seasons well with kiln or air-drying, with little degrade and very little shrinkage or movement.

Hardness. Hard (rated 2 on a 6 class scale) in relation to indentation and ease of working with hand tools.

Machining. Working properties variable. Cuts cleanly but may have a blunting or gumming effect on cutting edges. Cutting angle should be reduced to 20 degrees when planing quarter-sawn stock. Turns well.

Fixing. Kwila tends to split unless pre-bored, but holds fastenings well.

Gluing. Glues satisfactorily except with casein glues.

Finishing. It takes paint, stain and polish well, but gum bleed-through or oily patches may affect the finish.

Uses

Engineering. Cross arms, bridge building, piles, sleepers, posts, wharfing, mining timbers.

Construction. Framing, decking, treads, general construction.

Decorative. Furniture, especially outdoor settings and barbeque trolleys, turnery, panelling, joinery, shop fitting, cabinet making, parquet flooring, carving, veneer, counter and bench tops.

Others. Boat building especially for decking, vats, musical instruments and tool handles.

Identification features

General characteristics

Sapwood. Sharply differentiated from the heartwood.

Heartwood. Dark red-brown or yellow-brown in colour.

Texture. Coarse and even; grain often interlocked.

Wood structure

Vessels. Moderately large, visible to naked eye; short radial pairs or multiples and solitary cells. Sulphur-yellow and dark coloured deposits often visible. Vessel lines prominent on longitudinal surfaces.

Parenchyma. Abundant, aliform and occasionally confluent, with terminal bands present.

Rays. Moderately fine, not visible without lens.

Other features

Burning splinter test. A match size splinter burns to white ash.

Further reading

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

Bootle, K 2005, 'Wood in Australia: types, properties and uses', 2nd edn, McGraw-Hill, Sydney.

Hopewell, G (ed.) 2006, 'Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland, Class 1 and Class 10 buildings', books 1 and 2, Department of Primary Industries and Fisheries, Brisbane.

Ilic, J 1991, 'CSIRO atlas of hardwoods', Crawford House Press, Bathurst, Australia.

Standards Australia, 2000, 'AS 2082-2000: Timber - hardwood - visually stress-graded for structural purposes', Standards Australia.

Last updated 03 August 2010