Moisture Content
and Humidity
Because wood is organic and porous,
it is affected dimensionally by
changes in the amount of moisture it
contains. Solid-wood guitars are more
susceptible to the effects of changes in
humidity than laminated instruments
are, and therefore require ongoing
attention to their condition.
Protection From
Temperature and Humidity
Indeed, the greatest natural threats
to a fine wood guitar are extremes
of and rapid changes in temperature
and humidity. High humidity can
soften the glues used in building an
instrument, and can cause the top and
back (especially on flat-top and classical
guitars) to expand and rise—raising
string action too high. Or, if you live in
a drier, low-humidity climate (hot or
cold) or travel with your guitar to one,
evaporation of moisture from the wood
can cause shrinking and cracking. This
can happen no matter how old the wood
is, and string action can become too
low if the top and back shrink enough.
The ideal temperature for solid-wood
acoustic guitars is in fact normal room
temperature, which is about 70 degrees
F (21.1 C). The ideal humidity is about
40 to 50 percent. In winter, the heating
systems used in many homes can
drive temperatures up and humidity
levels dangerously low for guitars. A
good way to protect your guitar from
drying out is to use a room humidifier.
When an instrument is not in use,
it should be kept it in its case along
with a small guitar humidifier (of
which many are available). Do not
leave a guitar out for long periods
near a heating vent, radiator or other
heat source; do not leave it exposed
to direct sunlight; and do not leave it
in a car for long periods. The general
rule is to keep it safe from excessive
heat, cold, humidity and dryness.
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