Published in the Boston Classical Guitar Society Newsletter
Humidity is the most common culprit for wreaking havoc on the structural
integrity of classical guitars.
There are many ways in which humidity can damage your guitar, such as: cracks,
the bridge coming off, seams separating, action fluctuations
and therefore buzzing and intonation problems, even a loss in the
clarity of tone. Low humidity conditions are more detrimental to a guitar than high humidity
conditions. Two of the more serious problems, cracks and seam
separations occur in the winter when the humidity is low. With the
summer comes high humidity levels. Exposing your guitar to these
high humidity levels can literally cause your guitar to swell.
While high humidity levels do put stresses on your guitar, it is
often the lack of adequate humidity (in the winter months) that can
cause more substantial damage.
What is the ideal humidity level for a guitar? It depends on the
humidity conditions in which the guitar was built. Many Spanish
guitars are built at high humidity levels and develop cracks when
brought to the U.S. For example, Ignacio Fleta built in
Barcelona in fairly humid conditions, so you might want to keep a
Fleta around 60% relative humidity. I build my guitars at 40%
R.H. because I believe it is the safest humidity level to
promote the longevity of my instruments, it is also the median humidity
level for New England and most parts of the U.S. Most guitars
are content& nbsp; around 40-50% (feel free to contact me if you'd
like my opinion on the appropriate level for a particular
The frets can be an indicator of whether a guitar is under or over humidified. If the frets
protrude from the edge of the fingerboard it means that the
fingerboard has shrunk and the guitar needs to be humidified .
Conversely, if the fret ends are recessed into the board it means that
the fingerboard is swollen and needs to be dehumidified.
In order to measure the humidity level your guitar
is exposed to you need....a digital HYGROMETER (analog are often
inaccurate). Tags sells a reliable one for $25 (most hardware
stores sell them). Check the levels throughout your home.
You may find relocating your instrument from one room to the next to
be a very simple solution to your humidity problems. An air
conditioned room will have lower humidity than one that is
not. Dehumidifiers are also very effective at reducing high
Most important, make sure you keep your guitar humidified during the winter (never let
the guitar fall below 20% R.H.) There are basically two ways
of humidifying: using a humdifier(duh) or an in-case
humidfier of some sort. A simple and effective in-case
humidifier can be made simply from a film canisiter and a piece of
How to build a guitar humidifier
-Clean out a film canister so you're guitar dosn't smell like a
-Using a hole-punch, make a series of holes on the side of the canister
-Cut a piece of sponge to go in the canister
-Moisten the sponge, shake off excess so there is no chance of water
dripping form it, replace cap
-Insert the canister, top up,in the soundhole, between the g and d
strings. the tension from the strings should hold the canister in place.