Panels & Furniture Asia January/February 2018

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