Timber iQ February - March 2018 // Issue: 36 | Page 56

CONTRIBUTORS - WOOD WORKS The properties of sweet gum are summarised below for the wood enthusiast: SWEET GUM: HARD FACTS Botanical/scientific name: Liquidambar styraciflua (Family: Hamamelidaceae) Trade name: Sweet gum Other names: Liquidambar (South Africa); alligator tree, alligator wood, Liquidambar, redgum, sapgum, star-leafed gum, bilsted (US); amberhout (The Netherlands); satin walnut, hazel pine (Great Britain) Origin: US and central America Conservation status: According to the IUCN Red List of Threatened Species, its status is ‘least concern’. Bole characteristics: Sweet gum, in its natural habitat, grows to a height of 24 to 36m. A clear bole of about 17m long and 0.6 to 1.0m in diameter is commonly harvested. In South Africa, the tree usually grows to a height of 10m, although the maximum height recorded here is 30m. Colour: The heartwood is brown, tinged with red, often with darker streaks and the sapwood is creamy white. Grain pattern: The grain is often interlocked, producing an attractive striped figuring. The wood has a uniform, fine texture and satiny lustre. Density (at 12% moisture content): 560kg/m 3 (Ref. 1). On average 630kg, but anything ranging from 580 to 740kg/m 3 (Ref. 5). On average 560kg, but anything ranging from 490 to 620kg/m 3 (Ref. 6). Strength/bending properties: The wood is moderately strong and stiff with low to medium strength properties. Seasoning: The wood can be satisfactorily air- or kiln-dried. Thin stock tends to warp and twist in the early stages of drying, unless carefully stacked. After seasoning, the wood is dimensionally stable. Kiln drying: schedule 1 is recommended (see below). Durability and preservative treatment: The wood is moderately durable and permeable to preservative treatment. Working and finishing The wood saws, cuts and drills easily by hand or machine, with only a slight blunting effect on properties: tools. It planes well to a smooth finish, despite the irregular grain often encountered. The wood has good nailing, screwing and gluing properties and it takes all finishes well. Veneer can be readily stained to simulate a range of other woods, such as cherry, maple or mahogany. TIMBER DRYING SCHEDULE FOR SWEET GUM (Liquidambar styraciflua) Supplied by H-P Stöhr, Timber Drying Institute ([email protected]) Dry Bulb temperatures (°C) and Relative Humidity (%) at the following Timber Moisture Contents Drying schedule no. 1 Green 40% 30% 18% to final DB 1RH% DB RH% DB RH% DB RH% 35 77 40 65 45 53 60 32 DB = Dry bulb temperature, RH = Relative Humidity Please note: Drying schedules only serve as a guide to the kiln operator, with the response of the timber to the drying condition being the criterion. 54 FEBRUARY / MARCH 2018 //