Moisture Content and Humidity
Wood is a porous, organic material, and is affected
dimensionally by changes in the amounts of moisture
it contains. Fine guitars made from solid woods, are
without a doubt, more susceptible to the effects of
changes in humidity than laminated instruments, and
therefore require ongoing attention to their condition.
The moisture content of wood is determined by the
relative humidity and temperature of the surrounding
atmosphere.
Relative humidity is expressed as a percentage of
air's capability to hold moisture. For example, 30%
relative humidity means that the air is holding 30% of
the moisture it could possibly hold at a given
temperature.
The moisture content for wood and the relative
humidity for air are measured quite differently. In
wood, a 6% moisture content is present at 30%
relative humidity and 72 degrees F temperature,
(about 22.2 degrees C).
Protection from Temperature
and Humidity
The greatest threats to a fine wood guitar, are
extremes of, and rapid changes in, temperature and
humidity.
High humidity
can cause softening of the glues
used in the construction of the instrument. Also, as
the woods absorb moisture from the air, it can cause
the top and back, especially on flat-top and classical
guitars, to expand and rise - making string action
high.
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Conversely, if you live in or travel with your guitar
to a drier climate, (either hot or cold), there is another
danger. In areas of
low humidity
, the evaporation of
moisture in the wood can cause shrinkage and
cracking, no matter how long the wood may have
been previously aged. It also can cause the top and
back to shrink, making the string action low.
The collective experience of all of the major guitar
manufacturers today, has demonstrated that the ideal
temperature to preserve the integrity of solid wood
acoustic guitars is room temperature, which is about
70 degrees F (20.5 C). The ideal humidity is about
40% to 50%.
In the winter, the forced air systems used to heat
most homes, can drive temperatures up and humidity
levels dangerously low for guitars. A good measure
of protection against drying out your guitar is to use a
room humidifier.
When the instrument is not in use, we recommend
that you keep it in its case and use one of the small
guitar humidifiers such as "Dampit", available from
many instrument dealers. Do not leave the guitar out
for long periods near a heating vent, radiator or in
direct sunlight near a window.
Do not leave your guitar in the trunk of a car for
long periods and keep it away from excessive heat
and cold.
Please note: Damage caused to the guitar
as the result of exposure to temperature or
humidity changes will not be covered under the
Guild warranty.
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