Have you ever wondered why your
guitar plays great one day, yet feels
completely different on another? Suddenly
the fret edges are sharp or the action has
shifted and the guitar won’t play in tune
anymore. These changes can happen overnight,
especially in the winter. Cold, dry
weather brings low humidity and that
causes cracked guitars. Winter is my busiest
time of year for structural repairs, and
most of these repairs are preventable with
an inexpensive humidifier. I’ve been preaching
this message for more than two decades:
Preventive measures are the key to keeping
your guitar in top condition.
Dealing with humidity. Humidity is the
amount of moisture or water vapor in the
air. The more moisture in the air, the higher
the humidity. Lesser amounts of moisture
results in lower humidity.
There’s a popular myth that a guitar
sounds better when it dries out. Actually,
it just cracks and then I get to charge a
fortune to repair it. This myth is often confused
with a guitar’s natural aging process.
When a guitar ages, cells in its wood begin
to crystallize and harden, causing the guitar
to get louder and more dynamic. But if
it’s not properly humidified, the wood will
crack. (Did I mention structural repairs are
But you can have too much of a good
thing: When a guitar is over humidified,
it swells up and loses volume and tone.
(Think of a tub of lard with strings.)
High humidity can also cause finish
discoloration and even allow mold to grow
inside the guitar.
The way to avoid these problems is to
maintain a consistent humidity level for
your instrument—particularly an acoustic
hollowbody. This will prevent a host of ailments
and costly repairs.
Symptoms of low humidity. One of the
common telltale signs of a dry guitar is sharp
fret ends. When a guitar dries out, the fretboard
shrinks and the frets protrude beyond
the wood. Correcting this problem requires
re-humidification, conditioning, and fret
filing. If your guitar is showing signs of low
humidity (sharp fret ends, cracks, or separated
glue joints), you need to have it evaluated
by a reputable luthier.
This is what happens to a dry guitar in
various levels of low humidity.
LEFT: Fig. 1. This top cracked from lack of humidity. MIDDLE: Fig. 2. Fretboards can also crack as a result of low humidity. RIGHT: Fig. 3. The Humidipak guitar humidifier
system. Photo courtesy of Planet Waves
Below 35 percent humidity:
• Action (string height) changes.
• The top flattens out.
• Fret ends feel a little sharp.
Below 25 percent humidity:
• Fret ends become very sharp.
• There are drastic changes in the
• Seams begin to separate.
• There’s a slight separation between the
bridge and top.
• The finish starts to sink.
Below 15 percent humidity:
• Cracks appear in the top and body
• The bridge and fretboard crack (Fig. 2).
• The glue joints in the neck, bridge,
and braces begin to separate.
All of these ailments will greatly lower the
value of the instrument—not to mention your
enjoyment of playing it—so be sure to maintain
your guitar at the proper humidity level.
What is the best humidity level for my
guitar? Most experts say 40-50 percent. At
this level, a guitar will sound and play its
best. A great way to control humidity is to
use a humidifier. Think of it as an inexpensive
insurance policy to protect you from
very expensive repairs.
A guitar humidifier is easy to use and
very effective. Some guitar humidifiers are
suspended between the 3rd and 4th strings
and contain a damp sponge that needs remoistened
every two or three days. This
type of product works okay, but it’s not consistent.
The humidity will spike at first, then
slowly diminish as the sponge dries out.
The more modern guitar humidifiers
use a gel that not only emits humidity,
but also absorbs it if the humidity gets too
high. This technology was first developed
for cigar humidors, and now it’s available
for guitars. Planet Waves makes a
great humidity control system called the
Humidipak that uses this technology. I’d
also recommend using a hygrometer to
measure the humidity.
LEFT: Fig. 4. A room humidifier in action. MIDDLE: Fig. 5. Thanks to heat exposure, this bridge separated from the top leaving
a gap big enough to slide in a seam separation knife blade. RIGHT: Fig. 6. Use a wood conditioner to protect your rosewood or ebony fretboard.
Another great way to control humidity is
to use a room humidifier. This is a great idea
if you have multiple guitars in one room.
Humidifiers come in all shapes and sizes, but
be very selective, as some work much better
than others. I use a programmable humidifier
that utilizes both “warm mist” and “ultrasonic
technology.” It also has a built-in hygrometer
and a UV light to help purify the water. This
type of humidifier is much healthier than the
“cool mist” types that require a filter.
What guitars need to be humidified? All
guitars should be humidified, even electric
solidbodies. Newer guitars generally need more
moisture because the wood is kiln-dried, as
opposed to a vintage guitar made from air-dried
wood. The difference between kiln and air-dried
wood is dramatic. Kiln-dried wood uses
heat to dry the wood to accelerate the aging
process. However, these guitars require more
moisture to prevent warping and cracking. Air-dried
wood is more stable, especially in vintage
guitars, because the wood was generally aged
over a decade before being made into a guitar.
As a result, the cracked wood was removed
from the pile and used for something else.
Guitars made from air-dried wood still need
humidity to sound best, but they retain moisture
better than their modern counterparts.
Too hot to handle! Heat exposure can also
have destructive effects on a guitar. When a
guitar is left in the trunk of a car—especially
on a sunny day—the glue joints can fail.
Imagine the shock of opening your case and
finding a pile of wood where your guitar used
to be. Once again, I get to charge a fortune for
repairing heat-damaged guitars, so be vigilant.
A frigid nightmare. Cold is also an enemy.
When a guitar is exposed to low temperatures
and then brought into a warm environment,
the finish can develop checking. Checking
creates tiny hairline cracks in the finish—like
someone laid a spider web over the finish—
and you can’t polish this out. Finish checking
is permanent and can only be repaired by
refinishing (not something I would recommend).
Finish checking is basically the result
of the finish changing from one temperature
extreme to the other. This causes the finish to
expand and contract too fast, and that makes it
crack. To minimize this, when you bring your
guitar in from the cold, don’t open the case
until the outside of the case is at room temperature.
Even then, there’s no guarantee the
finish won’t check, but it will lessen the odds.
Okay, let’s review—here’s how to prevent
damage to your beloved guitar:
• Buy a guitar humidifier.
• Keep your guitar at between 40–50
• Use a hygrometer.
• Keep your guitar in a consistent environment
(one that’s comfortable for you).
• Keep it out of direct sunlight and out
of the car trunk.
These simple steps can save you hundreds
of dollars in repairs.
Nashville guitar tech,
has written five guitar repair books, all
published by Mel Bay. His bestseller, Guitar
Care, Setup & Maintenance, is a detailed
guide with a forward by Bob Taylor. LeVan
welcomes questions about his PG column
or books. Drop an email to guitarservices@
aol.com or visit guitarservices.com for more
info on his guitar repair workshops..