Hello amdoit, I believe what I have found is exactly what you need.
Traditional Hardwood Floor Mills Corporation (Miami, FL) is involved
in the ocean shipment of wood just like you and they have found a very
good solution. Here are two articles about their success:
Traditional Hardwood Floor Mills Corp. imports Brazilian rainforest
wood for luxury flooring. During ocean shipping, the exotic wood
became warped because of a time-limited packaging dessicant. With a
new, longer-lasting dessicant, the company solved its moisture
problem, and cast its worries out to sea.
Shipping goods from South American ports through the Caribbean
requires highly skilled navigation and patience due to unpredictable
seas. Crossing the tropics also subjects cargo to different climates
with varied temperatures and humidity conditions. These variations set
the stage for a destructive menace to damage cargo before it reaches
port. This stealth attacker is moisture.
To combat moisture permeation, Traditional Hardwood Floor Mills Corp.,
Miami, was placing porous bags filled with silica gel along the tops
of containers and underneath cargo before sending shipments of its
specialty wood products out of Brazil. This method proved to be
inadequate, Traditional says. The silica gel was not absorbing water
vapor adequately, and it stopped working entirely after 14 days. As a
result, the company lost 5 to 7 percent of this product per shipment
to moisture contamination.
The company found a solution by switching to Container Dri® II, a
desiccant technology from Süd-Chemie Performance Packaging. Moisture
problems have now been eliminated entirely. "Before, the company was
losing up to $5,000 per shipping container due to moisture damage,"
reports Wlamir Venturini, Traditional's president. "Since we started
using Container Dri® II, we have had zero loss."
The article is quite long and I think you will want to read the entire text.
Water affects the density of wood, changing characteristics like
color, texture and grain as well as its stability. Salt water, in
particular, also dries out the wood, causing it to warp. ?The most
important goal when shipping wood is to avoid altering its physical
dimensions,? says Wlamir Venturini, president of TFMC. ?If the wood is
changed in any way, then it is useless.?
This article is also worth reading fully.
This next article is in .pdf format. If you can open it, it is very
interesting and you need to read page 3.
After reading this information I think all of your questions will be
answered. However, if there is something you still need please ask for
a clarification and I will do my best to help.
Good luck with your future shipments, Redhoss
Clarification of Answer by
27 Jun 2005 06:31 PDT
I understand that your wood is not painted. I don't understand where
you get the idea that either of the articles refers to "painted" wood.
I re-read both articles and find no reference to paint. I even
searched both articles for the word paint and find nothing. I am
certain that the technique described in detail in the articles will
work for you just as well as it does for Traditional Hardwood Floor
I found some interesting information on the effect of moisture content
on wood that I think you will find helpful.
About Moisture and Wood
The durability of wood is often a function of water, but that doesn?t
mean wood can never get wet. Quite the contrary, wood and water
usually live happily together. Wood is a hygroscopic material, which
means it naturally takes on and give off water to balance out with its
surrounding environment. Wood can safely absorb large quantities of
water before reaching moisture content levels that will be inviting
for decay fungi.
Moisture content (MC) is a measure of how much water is in a piece of
wood relative to the wood itself. MC is expressed as a percentage and
is calculated by dividing the weight of the water in the wood by the
weight of that wood if it were oven dry. For example, 200% MC means a
piece of wood has twice as much of its weight due to water than to
wood. Two important MC numbers to remember are 19% and 28%. We tend to
call a piece of wood dry if it is at 19% or less moisture content.
Fiber saturation averages around 28%.
Fiber saturation is an important benchmark for both shrinkage and for
decay. The fibers of wood (the cells that run the length of the tree)
are shaped like tapered drinking straws. When fibers absorb water, it
first is held in the cell walls themselves. When the cell walls are
full, any additional water absorbed by the wood will now go to fill up
the cavities of these tubular cells. Fiber saturation is the level of
moisture content where the cell walls are holding as much water as
they can. Water held in the cell walls is called bound water, while
water in the cell cavities is called free water. As the name implies,
the free water is relatively accessible, and an accessible source of
water is one necessity for decay fungi to start growing. Therefore,
decay can generally only get started if the moisture content of the
wood is above fiber saturation. The fiber saturation point is also the
limit for wood shrinkage. Wood shrinks or swells as its moisture
content changes, but only when water is taken up or given off from the
cell walls. Any change in water content in the cell cavity will have
no effect on the dimension of the wood. Therefore, wood only shrinks
and swells when it changes moisture content below the point of fiber
Like other hygroscopic materials, wood placed in an environment with
stable temperature and relative humidity will eventually reach a
moisture content that yields no vapor pressure difference between the
wood and the surrounding air. In other words, its moisture content
will stabilize at a point called the equilibrium moisture content
(EMC). Wood used indoors will eventually stabilize at 8-14% moisture
content; outdoors at 12-18%. Hygroscopicity isn?t necessarily a bad
thing - this allows wood to function as a natural humidity controller
in our homes. When the indoor air is very dry, wood will release
moisture. When the indoor air is too humid, wood will absorb moisture.
Wood shrinks/swells when it loses/gains moisture below its fiber
saturation point. This natural behaviour of wood is responsible for
some of the problems sometimes encountered when wood dries. For
example, special cracks called checks can result from stresses induced
in a piece of wood that is drying. As the piece dries, it develops a
moisture gradient across its section (dry on the outside, wet on the
inside). The dry outer shell wants to shrink as it dries below fiber
saturation, however, the wetter core constrains the shell. This can
cause checks to form on the surface. The shell is now set in its
dimension, although the core is still drying and will in turn want to
shrink. But the fixed shell constrains the core and checks can thus
form in the core. Another problem associated with drying is warp. A
piece of wood can deviate from its expected shape as it dries due to
the fact that wood shrinks different amounts in different directions.
It shrinks the most in the direction tangential to the rings, about
half as much in the direction perpendicular to the rings, and hardly
at all along the length of the tree. Where in the log a piece was cut
will be a factor in how it changes shape as it shrinks. One advantage
of using dry lumber is that most of the shrinkage has been achieved
prior to purchase. Dry lumber is lumber with a moisture content no
greater than 19%; wood does most of its shrinking as it drops from
28-19%. Dry lumber will have already shown its drying defects, if any.
It will also lead to less surprises in a finished building, as the
product will stay more or less at the dimension it was upon
installation. Dry lumber will be stamped with the letters S-DRY (for
surfaced dry) or KD (for kiln dry).
Drying Times and Characteristics
Approximate drying times and drying characteristics of various
softwoods and hardwoods are given in Table I. Drying times in the
table represent the number of days needed to air-dry one-inch-thick
boards to a 15 to 20% moisture content. Times will generally be
shorter when weather is warm and dry, and can double in wet weather or
winter. Boards that measure 2 inches thick will take about 1.5 times
as long to dry as 1-inch boards. A moisture content of 15 to 20% by
weight is about the best that can be achieved by air drying in
Table I gives approximate drying times that vary with temperature and
humidity. Another way of telling if your lumber is dry is by testing a
sample board. Start by removing a board from the mid-section of the
pile. Crosscut a 1-inch piece from the middle of the sample board away
from any knots. Weigh the cut piece immediately (a fairly sensitive
kitchen scale should work). Now dry the piece in an oven or other warm
place at low temperature (225°F) for 18 to 24 hours. Weigh the piece
as soon as it is removed from the oven. Percent moisture content is
then figured by the following formula: [ % moisture content = ( wet
weight ÷oven dry weight ) -1 x 100 ]
If the moisture content is 15 to 20%, your wood is air dry.
Another method of determining dryness is to weigh a small board
periodically. The board is dry when its weight does not change between
You should read this in its entirety. It has a detailed discussion of warping.
Hopefully we have covered all that you need to know. The secret to
shipping your wood warp free is to follow the process used by
Traditional Hardwood Floor Mills Corporation.