Is Your Guitar Too Dry?

Learn to properly humidify your guitar, spot signs of dryness and avoid damage.

Damage Caused By Dryness

straightedge on guitar top reveals concave top
Guitar with concave top.

Shortly after heat systems are turned on I am frequently flooded with crack repair inquiries.

cracked spruce top
Open Center Seam

Open Center Seams

Nearly all flat top acoustic guitars have tops that are made from 2 pieces of wood. You will often hear the term "bookmatched top" as this describes the process of taking two pieces of wood cut from the same log, like pages of a book. These two pieces are layed open and glued down the center.
When dryness begins to flatten the top this seam is commonly the first to give way under the stress.

Are cracks covered by warranty? Cracks resulting from a lack of humidity or extreme heat are not the result of a manufacturing defect and therefore manufacturers do not cover this repair under warranty. Also be aware that some manufacturers will void the warranty of a very dry instrument.

Temperature Extremes

Dangerous environments include:

Heat is used to loosen glue joints on guitars for repair. Excessive heat can soften glue joints and allow them to loosen or slip. One of the most common predicaments I see on flattop guitars as a result of excessive heat is a sliding bridge. Once heated, the bridge can lift or actually begin to slide towards the sound hole. While this is easily spotted there are other areas of the instrument that can be adversely affected that are not as easy to spot. Frets, neck joints, braces and literally anywhere glue is used can be affected by heat.

Finish checking and crazing are often the result of temperature shock caused by taking a very cold instrument into a very warm environment suddenly.
When instruments are shipped or transported during the winter it is highly advisable to let the instrument slowly warm up to room temperature before removing it from the shipping carton or case.

lines resembling stretch marks in the guitar's finish
Severe Finish Checking on Mahogany Topped Gibson

Signs Of A Dry Guitar

Washboarding / Top Grain Prominent

This resembles a washboard in my mind. I personally use the term corduroy. These are raised lines in the top which are noticeable to the touch. The soft wood between the darker grain lines has lost its moisture and the grain now stands prominent. Warning: once this becomes severe cracks are usually imminent. Take heed, this may be your last chance to avoid cracks.

Dried Spruce Guitar Top
Lines, which resemble corduroy are a common sign of dryness.

Sharp Fret Ends

The fingerboard has shrunk due to the loss of moisture but obviously the metal fret wire does not. The frets are now wider than the fingerboard and the sharp ends can become apparent. yow! This is particularly noticeable on unbound fingerboards.

Action (String Height) Lower

The top has begun to flatten out as it looses moisture and the action is lowered as a result. The fingerboard extension (portion of the fingerboard which is glued directly to the top) may also sink a bit causing a bend in the area where the neck and body join.

Concave Top

After dead flat comes concave. If you've gotten to this point without a crack you are very lucky.

Cracks / Opening Seams

After a fair amount of moisture loss an instruments wood panels begin to shrink. Eventually this change can prove too stressful for the wood and it cracks.
If left unattended these cracks can spread open and create even more costly and highly visible repairs.

Ideally, humidity should be kept around 45%.

How do I humidify my guitar?

When the humidity in your home is very low (say 20-35%) it is best to use a room humidifier in conjunction with an instrument humidifier. If the air is very dry, a small sponge is likely to be insufficient. And for those with a collection of instruments, refilling instrument humidifiers could be quite a chore, easier instead is to control the rooms humidity with a room humidifier.

Where To Start

Too Much Humidity?

The reason it's important to use a hygrometer is to determine the humidity levels in your home. While low humidity is very common in the winter here in Virginia, not all areas share our troubles. In the summer humidity levels generally stay around 50% and above, eliminating the need for humidifiers during those times.

Instruments that find their home on islands and states where humidity is very high can also be affected by the high humidity and rather than needing additional moisture, they need less.



Anytime a humidifier is used with an instrument it is essential that water is not allowed to drip into the instrument. If enough water is spilled inside of an instrument the wood can swell and create finish damage or haze.
Also keep in mind that, depending on your location, humidity levels may increase during the summer and eliminate the need for a humidifier.

Silica Gel Packets

packet The purpose of the silica gel pack is to absorb moisture and keep everything dry. Unless you are living in a humid area these are not necessary and can do harm. Apparently it is the case manufacturers who place them in the case.


It is usually best to store the instrument in the case. Not only does it protect it from damage, the case can offer more protection from severe and sudden environmental changes.


Guitar Humidifiers

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