Timeless Tips
WEATHER
In addition to fungi, weather is the other cause of wood deterioration.
The major factors in the weathering process are:
- Ultraviolet rays (sunlight)
- Water
- Temperature
- Abrasion
Ultraviolet rays - UV causes a breakdown
in the lignin component of the wood cell which gives rise
to color changes. Light woods tend to darken and gray. Dark
woods bleach out and gray.
Water - It plays a major role in weathering
of wood. As UV causes lignin to degrade, water washes away
surface cellulose fibers that have been released due to the
breakdown of lignin. As these surface fibers are washed away,
new fibers are exposed and the cycle continues. Water also
causes swelling and shrinking of the new wood surface, developing
cracks which expose new wood fibers to UV breakdown.
Temperature - It is not as critical a factor
as UV and water, but increased temperature accelerates the
deterioration process caused by UV. For log homes, elevated
surface temperatures will increase the rate of moisture release
within the logs thereby causing more checking. That's why
it's a good idea, especially on new log homes, not to use
dark color stains, since darker colors will absorb and hold
heat and accelerate the release of moisture. Also, freezing
and thawing of absorbed water contributes to checking as well.
Abrasion - The mechanical action of wind,
sand, and dirt can be an important factor in the rate of surface
degradation and removal of wood. Small particles such as sand,
can become lodged in surface cracks and through swelling and
shrinking, weaken fibers in contact with it. Solid particles
in combination with wind, can have a significant sandblasting
effect. A log home in a treeless field is especially vulnerable
to abrasive weathering.
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