chemical with a different color.
In the living tree, the chemicals
are not exposed to oxygen or light,
so oxidation does not occur very
quickly, if at all. However, once
the tree is harvested and the logs
are sawn into lumber, exposure
to air and light (for the first time
ever) can result in rapid oxidation.
This oxidation may proceed slowly
(months) or happen quickly (days
or hours). Color changes in lumber,
often with dark woods getting
darker, and light woods getting
lighter or darker, will happen naturally. Sometimes the color change
is more than just darkening...for
example, walnut can be green when
first sawn, but changes to chocolate
dark purple streaks in yellow poplar
fade or can change to black.
In a few cases, these chemicals
in the cells will move, before or
after oxidation, with the water as
the wood dries and then become
concentrated at or near the
surface when the water evaporates
but leaves the chemicals behind.
This often is seen as a surface
color that can be planed off. In a
few cases, I have seen a stronger
oxidizer chemical used in finishing to create an instant aged look.
As a result of the oxidation
of chemicals in the wood, it is
common to see the wood’s color
change between when it is first
sawn, to when it is stacked for
drying, to when it is done being
dried, to when it is pulled from
storage, to when it is manufactured, to when the consumer first
gets the product, and to later in
the life of the product. Depending on the exposure, especially
exposure to light, or being partially sheltered from light, the
color change can be fast and/
or erratic. Most of the time, the
color change is only several 1/100
of an inch deep, so sanding can
WOOD DOCTOR’S Rx
Find out more today.
Cutting Edgebanding Material Handling CNCMachinery Sanding Optimizing