How Does Humidity Affect an Acoustic Guitar?


A few months ago I was retrieving one of my acoustic guitars from my parents´ house. Norway is generally a fairly cold country, and the guitar had been placed in one of the colder rooms that had been heated up sporadically during the freezing winter months. So, when I was on the train back to Oslo, I began to wonder:

How does humidity affect an acoustic guitar? When your guitar is exposed to too low – or too high relative humidity levels, you are putting it at severe risk. To avoid cracked guitar bodies, bridges flying off, mold and reduced string action, you need to make sure that the humidity levels are within the 40-60% range.

If you’re not sure whether your guitar has been kept in the 40-60% range, you will definitely know after reading this post. Let’s look into what symptoms your guitar might have and what we can do to protect and repair it.


How Temperature Affects Your Guitar

It is fairly easy for us to go straight to temperature when we think of this topic. I certainly did. But as you will discover in this article, the humidity relative to the temperature is what we need to monitor in order to protect your guitar. This one of the most serious issues that can severely damage your guitar, so you need to know how to protect it.

A quick rule of thumb is that guitars actually like the same kind of environment that we enjoy!


Relative Humidity: the Real Danger

Too low or too high humidity levels can seriously affect wooden instruments like an acoustic guitar

I am a musician, not a scientist, so I will explain humidity fairly simple: humidity is a measure of the amount of moisture in the air and is invisible to the naked eye. The air we breathe can hold different amounts of this gaseous-state water, depending on whether the air is hot or cold. 

When the air is hot, it can hold more water than when it’s cold. So, the humidity levels in your area are higher in the summer than in the winter.  

All of us know how the different humidity levels feel like. If you wear glasses, you have experienced that they get really foggy the second you step inside your house on a cold winter day. This is because once the cold air comes into the house and is heated up, the humidity levels relative to the temperature are lower.

This is what causes our skin to get cracked (Xeroderma) as well as making our lips and noses sore. If you have asthma, you have probably noticed respiratory problems due to the cold, dry air as well.

When it’s summer, however, you can barely manage to take off your t-shirt because the high humidity levels make it so sticky. This is because the sweat does not evaporate, thus failing to cool us down. 

So, we feel uncomfortable when the relative humidity levels are too low or too high. 

…and so will your guitar.

Many guitar stores have dedicated rooms that consistently maintain the humidity levels. Then, both the player and the guitar are happy!

The Optimal Humidity Levels

Relative humidity (RH) is expressed as a percentage.

Most of us prefer and feel most comfortable in humidity levels of 30-60%. Your guitar is no different. If you want to avoid cracked bridges, shrinking fretboards and other damages to your precious guitar, you need to make sure that the humidity levels are within the 40-60% range. 


Potential Damages to Your Guitar

Generally, an acoustic guitar is composed of wood, steel and some plastic pieces, like the bridge pins (the pins that lock the strings to the bridge).

The steel components like the machine heads and strings will hardly be affected by temperature, but the wood can be severely damaged when temperature changes and the relative humidity drops or rises.

When relative humidity is below 40%

The air is too dry.

  • When the relative humidity is below 40%, the guitar top might start to sink in, which might cause the string action to lower as well. This will make your guitar much harder to play. 
  • The bridge can start to separate from the body and eventually just snap right off.
Two ukuleles without a bridge.

This has actually happened to two of my ukuleles. One of them was rarely used, so it was just placed in the window for a whole year. Eventually, one day I heard a large “CRACK!”… The bridge had snapped right off. 

My second ukulele was just hanging on the wall, right next to a radiator which was frequently turned on and off during the winter. One day, the bridge just flew right off.

  • The guitar body will get cracks.
  •  The fretboard will shrink.

When relative humidity is above 60%

The air is too wet.

  • The opposite happens. The guitar top will swell up, causing your string action to lift higher. This will also make your guitar feel harder to play.
  • If you have ever found an old guitar in the cellar, you might have noticed that the sound it produces is quite dull. This is due to the guitar being exposed to high relative humidity levels. In other words, don’t store your guitar in a wine cellar!
  • Due to the swelling, the strings will eventually fly off. 
  • You may start to see mold on your guitar. Not recommendable. 
The strings´distance to the fretboard can sink or rise if the guitar is exposed to low or high relative humidity.

How do I Know What the Humidity Levels are?

If you want to know what the humidity levels in your room are, you need to get your hands on a Hygro-Thermometer.  This is a device that measures the humidity of the air. When you measure the humidity, try to walk around the room to see if the humidity levels are changing. Often times there are better conditions for your guitar in closets or away from radiators. So if you can, relocate your guitar the spot where the humidity levels are within 40-60%. 

The highly reputable guitar brand Taylor offers both a mini version and a big digit version of the hygro thermometer:

The Mini: Good to keep in the guitar case along with your guitar.

The Big Digit: Good to keep in a room filled with several guitars.


How Should I Store my Guitar?

My guitar is mostly displayed on a stand. Right in front of my Pokémon stuff.

Actually, the best place to store your guitar is in its guitar case. The hardshell cases to be more specific. But I’ll be the first to admit that I am very lazy with this myself. My guitar is being used quite often, so I like to have it on the guitar stand.

But from now on, I will keep it in a hardshell case during the wintertime to protect it as best as possible. 

Having your guitar on a wall mount or stand in the winter is not optimal. You see, when stored in a cold room, sudden hot air from radiators can cause the temperature to rise quickly, rendering the relative humidity too low. 

And thereby causing the guitar to find itself below the relative humidity of 40%, which spells trouble.


Steps you can Take to Protect and Restore Your dry Guitar

– How to protect your guitar?

In most cases, the most common issue is that your guitar might dry out in the winter. That is why I have provided a couple of solutions for you, whether you own one, or multiple guitars.

In a hardshell case – single guitar

You don’t need to spend a ton of money to protect your guitar and to keep it in the humidity level sweet-spot of 50%. You can just get your hands on the Humidipak from D´addario. This will carefully adjust the humidity levels, regardless if it is too low or too high. This is called a two-way humidity control and will help you monitor the humidity levels surrounding your guitar.

This is an easy and effective way to maintain your guitar so it won’t be too dry or too wet. If you are storing your guitar in its guitar case, the Humidipak will make sure that it is always right in the sweet spot. Not only that, but it will also improve your guitar so it feels much better to play!

How to use a Humidipak in the guitar case:

  1. Put the Humidpaks inside the black pouches that come with it. These will need to get refilled once they feel like hard crystal.
  2. One goes underneath the little area below the guitar neck. This pouch will protect the wood in the neck area.
  3. The other one hangs between the G and the B string and down the soundhole, protecting the guitar body.
  4. Each pack will last between 2-4 months. 

The Humidipak costs so little compared to what you would have to pay to get your guitar repaired or having to buy a new guitar. Especially if you already have spent thousands of dollars on it. I wish I had done this sooner myself, but at least now I know!

Since it will provide moisture to a dry guitar it may even start to heal minor cracks. However, D´addario themselves do inform that it cannot fix severe cracks. And you should also re-humidify the guitar before using the Humidipak as a maintenance system.

You can check the current price of the Humidipak on Amazon if you are interested.  

In a room with several guitars

Do you have several guitars hanging on the wall in your room? Well, you might not wish to get a hardshell case for every single one. Or, you just really want them to hang on your wall, for anyone to see, whatever time of year.

Then you can take a look at the room humidifiers, like the TaoTronics Humidifier, which is designed to provide humidity to your guitars.

If you have a room filled with guitars that might run the risk of drying out in the winter, this might be your solution. If you are interested in the TaoTronic Humidifier, you can check the current price on Amazon.


What if my Guitar has Begun to Crack?

After I began doing the research, I found out that my guitar was in fact too dry. It had been exposed to low relative humidity for too long. And whilst the Humidpak is good for maintaining the humidity levels, it won’t fix severe, permanent damage to your guitar. 

Luckily, there were not any big cracks that would need gluing. But I could see smaller cracks starting to form. 

However, it was not beyond salvation!

If your room has low relative humidity below 40%, chances are that your guitar has become too dry and major cracks may start to form. In order to restore the moisture of your guitar and to allow the guitar to expand its wood to seal cracks, you need to get a humidifier

Humidifier

  • It can be a little tank filled with distilled water. The Oasis Humidifier is a great option. You fill it with water and put it underneath the strings over the sound hole. This humidifier will create a chamber of humidity, constantly providing humidity for your guitar. 
  • Or it can be a sponge, like the D´addario Acoustic Guitar Humidifier. Soak the sponge, twist it and put it in a black cage that comes with it. This is placed between the strings over the soundhole. If the sponge is completely dry after the next day, soak it again and repeat until some water is still left in the sponge. Now you know that your guitar has absorbed the amount of moisture it needed. Yay!

Rehumidifying your dry guitar with one of these products will do wonders, so give this a try before taking your guitar to the repair shop! You can check the price on the Acoustic Guitar Humidifier on Amazon.

If you are worried about putting objects filled with water through the soundhole: don’t worry! Both methods are considered safe for your guitar.

This is a process that may take several days. But by the end, you will be amazed b what this solution can do to your guitar. 

Dehumidifier

When it is the other way around; when your area has high relative humidity above 60%, your guitar is probably too wet and swelling of the guitar top will happen. Then you must get a dehumidifier.

It consists of material that absorbs moisture from the guitar. For example, the Guitar Humidifier Set from Taylor Guitars is made of Bamboo Charcoal, which attracts excessive moisture from the guitar.


As I mentioned earlier in this article, the most common issue is that your guitar dries out, so the solutions provided are mostly towards that issue.

If you are in the market for a new acoustic guitar, you can also check out this page to see my favorites.

Suggested Further Reading:

Thomas Leypoldt

Hey there! My name is Thomas and I have been a film composer for over 10 years, delivering music to feature films, documentaries, video games, and commercials. I share everything I have learned on this website, to hopefully be of help to your own development as a musician.

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