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There can be vast quality
differences from one hardwood to the next, especially
with more of the lesser known manufacturers of exotic
hardwoods, unfinished and prefinished. By looking at the
properties of a tree once it's cut down
in the forest to
the time the final product is installed in your home,
one can get a better idea how moisture and
hardwood react with one another.
When hardwood used
for flooring begins it's trail from the forest to your home it loses a lot of
moisture content.
Looking at it from that standpoint, once a rough sawn
board is produced it is generally cut into one inch thickness and eight foot
lengths. Width will vary depending on how much good usable material is taken
from each individual log. At this point a typical board can weigh as much as
much as 60 pounds; some more, some less depending on the denseness of the
hardwood specie. Using this weight as an illustration you will see how much
weight and moisture is lost during the drying periods.
Stick Or Open Air Drying
Most hardwood mills have their own
drying areas. The next step calls for air drying
outdoors. Products are cut to similar dimensions from
the log for another reason; to allow for proper
stacking. Without doing so boards will take on new
shapes during which time moisture will be lost.
As example, think of any
type of wood product you may have left outdoors that was
affected by the elements. How about all those 2'x 4's
sitting in a pile next to the shed outdoors. What were
once straight boards when purchased are now crooked
in all directions. With air drying, boards are stacked
on top of one another and separated by sticks; also
called stick drying.
During this procedure lumber is
stacked proportionally and stickers are inserted between
the boards, running vertical to the width of the boards.
This allows air movement to pass through during a drying time of two
to three months. Once this
period has passed our example board has actually lost
25% of the moisture it had at the beginning. It now
weighs in at 45 pounds.
Dimensions have also changed with
the exception of the length as solid hardwood only
expands by width and thickness in this case. The board
has lost approximately 1/32" in thickness and 1/4" in
width (12 inch board). We haven't even seen the kiln drying process, so
you can just imagine what happens to the flooring once it is
brought down to the moisture content it needs
before it can become viable flooring material.
Kiln Drying
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