Affects of Temperature and Humidity

Lack of proper humidity has the potential to damage musical instruments. Shortly after the seasons change and heat systems are turned on I am flooded with crack repair inquiries.

Are cracks covered by warranty? Cracks resulting from a lack of humidity or extreme heat are not the result of a manufacturing defect and manufacturers do not cover this repair under warranty.

Temperature Extremes

Dangerous environments include:

Heat is used to loosen glue joints when performing certain repairs. Excessive heat from undesirable environments can soften glue joints and allow them to loosen or slip. Frets, neck joints, braces and literally anywhere glue is used can be effected 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. This is primarily seen on lacquer finishes.
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.

Signs Of Dryness


This resembles a washboard in my mind. I also use the term corduroy.

The picture below is of spruce, a soft wood that is among the first to show the effects of dryness.

Warning: once this becomes severe cracks are usually imminent. Take heed, this may be your last chance to avoid cracks.

dry spruce top

Sharp Fret Ends

A dried out fingerboard can shrink considerably. While it's gotten smaller the frets have not, the edges of the frets now hang past the edge of the board causing sharp fret ends.

Action Change (Strings Closer To Frets)

A dry top can flatten, and under extremes, become concave. Once the top begins to loose it's arch it, and the strings, go lower.

Cracking / Opening Seams

After a fair amount of moisture loss an instruments wood panels begin to shrink. Eventually this change can prove to 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 Mandolin?

I counter that question with another...what is the humidity level in your home?

A home who's relative humidity drops quite low, lets say 25% during the winter, will require a more aggression system than one who is housed in a more humid environment. While an instrument humidifier is a good first step, it can't solve all of your problems.

When the humidity in your home is very low it is best to use a room humidifier in conjunction with a soundhole or case humidifier. Asking a small sponge to counteract that kind of dryness is asking a bit too much.



Anytime a humidifier is used with an instrument it is essential that water is not allowed to drip into the instrument.
Also keep in mind that, depending on your location, humidity levels may increase during the summer and alleviate the need for a humidifier during that time.

Silica Gel Packets

silica gel pack inside guitar case 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 and they are often left there even after the instrument is welcomed.


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.

See also: Cleaning Instrument Finishes

See Also: Cleaning Finishes


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