Panels & Furniture Asia January/February 2018

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62 WOOD CLINIC Dear Mr Shim, A READER'S EMAIL Mr Shim (Shen Yuxin) I have just joined a small carpenter's shop that makes bar counters and stools. However, I do not yet know how to identify wood species. Can you offer some tips on identification? Our bar counters are made using 5-inch thick slabs of rift cut log and there are often large cracks. We use a mixture of ferrous glue and sawdust to fi ll these cracks. However the patched area tends to bulge after some time (Fig. 1). Can you advise us on these problems? Yours Sincerely, Mr Sarin Indonesia ASK MR SHIM HOW TO IDENTIFY INDONESIAN TIMBERS AND FILL UP CRACKS (I) Idenfying Indonesian mbers 1. Hardwood: Annual rings are generally less distinct; cells mainly consist irregular vessels, tracheids, wood rays, parenchymas and fibres. Hardwoods with medium or high density are the most common, although there are also low-density species. 2. Sowood: Also known as coniferous timbers, softwood’s annual rings are distinct; cells mainly consist regular-sized tracheids, wood rays and parenchymas. Wood is mostly soft; there are some species that have high density. Only two types of softwood are common in Indonesia: Merkusii pine and Philippine Agathis. 3. Characteristics: Observing the radial, lateral and cross section of the wood can help identify its species. i. Colour: Wood species such as Kapur has a light bluish yellow sapwood and pink heartwood (Fig. 2). ii. Odor: Timber such as kapur smells of camphor when sawn apart. Fig. 1: Glue line showing the patched area bulging out after patching with a mixture of ferrous glue and sawdust. Fig. 2: When Kapur is sawn apart, the sapwood is light bluish yellow, significantly different from the pink heart wood. iii. Specific gravity: Belain or Ulin, for instance, has an air-dry density of around 850-1100kg/m 3. iv. Annual ring: Indonesian hardwoods have less distinct annual rings, except a few species such as the lacquer tree (or Rengas). According to the distribution of the vessels, hardwoods can be divided into diffuse porous hardwood and ring porous hardwood. For example, Dark Meranti and Merbau are ring porous hardwoods. January / February 2018 • Issue 1 • PANELS & FURNITURE ASIA
WOOD CLINIC 63 Fig. 3: The heart wood of Kapur contains crystalline resin that is as white as borneol. Fig. 4: Clear resin canals on a cross section of Dark Meranti under a magnifying glass. v. Heart wood is usually brile. Some species have more extract and are heavier in weight. For example, the heart wood of Kapur contains crystalline resin that is as white as borneol (Fig. 3). For some species, the heart wood and the sapwood are particularly distinct, such as Rengas. vi. Sapwood is usually pale yellow or white. Some species like rubberwood display no difference in colour for sapwood and the heart wood. vii. Wood grain: Common wood grains include straight grain (Belain); wavy grain; spiral or diagonal grain; interlock grain (Dark Meranti). viii. Texture: The thickness of the texture can be distinguished by observing with the naked eye or touching dressed wood surface. ix. Wood rays: Observe the thickness, colour and luster of dressed wood’s lateral section with a magnifying glass. x. Cell extract: Observe the dressed wood surface with a magnifying glass. xi. Latex can be seen at the end of the log for some species, such as Merbau. During sawing, the band saw blades will be stained by latex. xii. Resin canal: Dark Meranti has clear resin canals (Fig. 4), one of the main features to help identify wood species. xiii. Oil may be found on the wood’s surface after being dressed, for example, Keruing. The oil is more obvious when seen from the cross section. xiv. Minerals contained in wood cells may not be the same. For example, in the vessels on the lateral or cross section of Merbau, yellowish minerals such as sulfur are obvious (Fig. 5). (II) Patching up cracks in 5-inch thick slabs of ri cut log: When the log is cut into 5-inch thick slabs, the moisture content in drying wood is uneven or over 16 per cent. In an air-conditioned room, for example, the moisture content may only be nine per cent, resulting in wood drying and contraction. As the mixture of ferrous glue and sawdust is very solid, the glue film becomes very hard and anti-solvent. As a result, it cannot contract simultaneously with the wood and thus bulges. The moisture content should be controlled at 10 ±2%. I hope the above analysis helps. Fig. 5: The vessels on the Merbau cross section contain many small yellow dots of sulfur, visible to the naked eye. f you encounter any problems with wood bonding in timber Imanufacturing or wood processing, don’thesitate to ask Mr Shen Yuxin immediately! Mr Shen Yuxin was born in 1948 in Kuching, Sarawak, Malaysia. In 1974 he graduated from the Department of Forest of National Chung Hsing University in Taiwan, and then worked in Taiwan Forestry Bureau. From 1975 to 1995, Mr Shen engaged in wood processing and wood-based panel industry in Malaysia, Singapore, Kalimantan island country, and served as the engineering and technical personnel, production director, production manager, as well as general production manager. Mr Shen also entered world famous Asian Chemical Company woodworking group in 1996, and worked as the regional director of technical services. PANELS & FURNITURE ASIA • Issue 1 • January / February 2018
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MICA (P) No: 138/05/2017 • ISSN:
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2018 by Panels & Furniture Group 4
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6 NEWS FAO: GLOBAL WOOD PRODUCTION
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8 NEWS CHINESE STUDENTS REIMAGINE T
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Page 17 and 18: PANEL MANUFACTURING 15 His cousin R
Page 19 and 20: PANEL MANUFACTURING 17 now. We want
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Page 39 and 40: (Cubic Metres) 2,500,000 MATERIALS
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Panels & Furniture Asia January/February 2018

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