In order to provide the
finest, furniture grade home, Bali Wood Houses
has researched countless finishing processes used not only in hardwood and
log home construction, but also in the fabrication of furniture, wood art
and fine musical instruments. A key element common to the finest wood
products is seasoning or aging of the wood after it is milled into
For many years we
falsely believed that the gold standard for wood processing was Kiln
Drying. We are not saying that kiln drying is always inappropriate, since
we fully agree that some furniture applications require lumber with very
low moisture contents that cannot be achieved with natural air drying,
aging and seasoning.
Kiln drying is quite
appropriate for many wood species. For example in the United States, oak
is the dominant hardwood that is kiln dried and successfully used for
furniture and flooring for centuries.
However, neither oak
nor vast majority of other wood species can match Bangkiraiís properties
1) Unequaled Termite
2) Extreme hardness
3) Very High density
4) Tendency to leach
extractives over months (or years if kiln dried)
Some wood species that
are kiln dried may be immediately finished without being seasoned.
However, none of these species is termite resistant like
OPEN AIR DRYING
Based on research
performed by Akzo Nobelís Sikkens © coating division, we have learned that
kiln drying of some species such as Bangkirai prolongs the extraction of
tannins and other extractives that if left in the wood will ultimately
result in failure of any finishing method.
All hardwoods should therefore be
left uncoated for as long as possible, and be air dried in the open (for
instance during the assembly process) until all extractives have leached
from the timber fibers and the timber is thoroughly dry (*). For oily resinous
timbers such as Merbau a minimum of 3 months is
recommended. For very dense, slow drying timbers such as Bangkirai a
minimum of 6 months is necessary. During this seasoning period we must
regularly clean all wood surfaces to remove the extractive materials that
leach from the wood as it seasons such as tannins, as well as ensure that
the moisture content stabilizes and adjusts to the surrounding climatic
conditions. The method for regular cleaning is critical and if not done
properly or carefully can damage the wood and affect its termite
resistance. It is therefore not an advantage at all to assemble a wooden
prefab house under cover since weathering will be prevented (no sun, no
rain) and thus the proper drying of the wood is at stake (*).
(*) Source: Akzo Nobel Sikkens, Australia
The requirement for
proper seasoning is independent of whether the finishing method is
French Polishing, or Cetol.
Properly Seasoned and Finished
Since the many islands
in the Caribbean and the Pacific and Bali share similar climates, the
resulting moisture content internal to the wood will be very close to the
equilibrium moisture content that would be achieved and required for homes
destined for those areas.
Please note that kiln
drying does not remove extractives from the timber fibers and generally
dries the wood beyond equilibrium conditions. Exposing kiln dried
hardwood to tropical climates causes the extractives to begin leaching
(but at a much slower pace) and the wood slowly increases its moisture
content. This leaching will cause flaking and failure of any coating
system applied to the wood (French polishing, polyurethanes, Cetol, oils,
etc.) and the absorption of water will cause the lumber to distort. The
reason that kiln drying slows the leaching process is because the internal
moisture of the lumber is a major mechanism in transporting the
extractives to the surface of the wood where they can be removed.
The weathering that
occurs during the seasoning process has several aesthetic affects:
1) The color and grain
contrast deepens. This is quite desirable.
2) Some very small
surface cracks will result. These are removed during step 6
of our seasoning process discussed below.
3) Some graying of the
exterior surfaces will result. This is fully removed during sanding (step
6 of our seasoning process discussed below) but does not affect.
The commercial lumber
industry could not possibly store and process enough wood to properly
season it. Kiln drying is a more rapid method by which they can deliver a
useful (though far from ideal) product.
When Bangkirai is not
properly seasoned, the near term consequences on the finish are shown in
the figure below which is a photograph of a one-year old gazebo post (not
built by us):
Consequences of Improper Seasoning
Seasoning of wood for
use in our homes is a multi-step process.
1) The timber is
harvested using only sustainable forest practices and is sent to a mill
where it is cut into the various required sizes. The time from milling to
delivery ranges from 1 to 2 months.
2) Our factory receives
the wood and immediately performs our proprietary process cleaning to
remove the extractives that have already migrated to the surface.
3) Seasoning continues
at our factory during the hot season when rain is rare. Stacked lumber is
rotated to maximize exposure to the heat of the sun and accelerate the
4) The lumber is used
to construct your home before it is fully seasoned. For this reason, we
fabricate many homes simultaneously and do so in the open where the lumber
is exposed to the sun and elements. This exposure more thoroughly exposes
all surfaces. The fabrication time is intentionally extended as necessary
to ensure that the extractives are thoroughly removed prior to any
5) Any boards
exhibiting cupping or distortion are straightened or replaced.
Straightening requires us to dismantle the boards, turn them, recondition
the lumber, fix them tightly back to the support beams (or clamp them) and
allow the boards to return to equilibrium stress conditions. In the vast
majority of the cases the boards return to their original straight shape.
If further cupping occurs, we repeat the process or replace the board.
6) All surfaces to be
finished are rough and finish sanded, after assembly to remove the final
traces of extractives and prepare the wood to receive the final finishing
The above process is both time consuming and expensive. However, without
taking these steps we cannot provide the quality product our reputation
demands and our customers deserve.
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