In this article I'd like to talk about the role that humidity plays in the construction of guitars, what effect humidity levels can have on your guitars, and finally some practical ways that you can monitor and regulate humidity levels to facilitate proper environmental conditions for the optimal performance of your guitars.
The Role Of Humidity In Guitar ManufacturingWhen building a guitar, the humidity in the room is crucial. Many factories and plants that manufacture guitars are climate controlled to maintain a constant relative humidity level. Significant variations in humidity levels can cause wood to contract or swell, making consistent measurements on a day to day basis effectively impossible.
Taken from Taylor's website:
"Our factory is climate-controlled to maintain a temperature of 74 degrees and a relative humidity of 47 percent. This consistency causes the wood to equalize at a specified moisture content ideal for building guitars. As the wood’s moisture content changes, so does the size of the wood. Spruce, in particular, shrinks and expands a tremendous amount as it gains and loses moisture. For example, let’s say we condition a spruce top in a room that is 47 percent RH, and then cut that spruce to a width of 16 inches. If we then were to lower the room’s RH to 30 percent, that same piece of spruce would shrink to 15.9 inches in width — shrinkage of almost 1/8 of an inch!"
(read the whole article here)
Most guitar manufacturers maintain the relative humidity at their facility in the range of 45% to 55%. This is because when guitars are built and shipped to locations around the world with varying degrees of humidity, they will still perform properly within a reasonable proximity on either end of this range. If a facility was hypothetically building guitars in a facility with a relative humidity level of 65% for example, the guitars would almost always dry out once they reached their destination and in some cases would dry out so much that they would be damaged.
The Effect of Humidity Levels on Guitars
Guitars can be adversely affected by conditions that are both too dry and too humid. It is important to make sure your instruments are being kept in a stable environment where the relative humidity is within the range (ideally) of 45% to 55% humidity. That said, keeping your instruments within a reasonable proximity to that range will likely not damage them.
Symptoms that your guitar is being negatively affected by dry conditions (very low humidity levels) may include:
Sharp fret ends. This occurs when the wood of the fretboard contracts under dry conditions.
Front bow in the neck. This can cause buzzing on the upper frets that can't be fixed by raising the action unless it is raised extremely high.
Fretboard "bump" at the 12th or 14th fret. Where the neck connects to the body dryness can create an upwards "hump" on the fretboard.
On acoustic guitars, a sunken top or flat back. Low humidity can cause the top of acoustic guitars to sink inwards, and can cause the back of the body to flatten out.
In extreme cases of dryness, wood can crack, glue joints can split or need repair, and finish can crack.
While exposure to high levels of humidity can in extreme cases be just as detrimental to your guitar as dryness, it is not as common of an issue as exposure to dryness. If you are worried that your guitar is exposed to too much humidity, some symptoms to look out for include:
Swelling of the body. Opposite to the effect of dryness, too much humidity can cause the body of your guitar to swell out.
Unplayably high action. As the body of the guitar swells, the bridge rises up causing the action to become unplayably high.
Monitoring and Regulating HumidityIf you are worried about the humidity level of the environment where your instrument is stored, one simple and free method of protection you can use is your guitar case. Storing your guitar in its case will protect it to a certain extent from the conditions outside, but this is by no means a perfect solution. If you want to ensure your guitar is being stored in an environment that will not cause it damage, you will need to monitor the humidity level.
The best way to monitor the humidity level of your environment is by using a device called a "hygrometer".
This hygrometer is great because it is small enough to be kept inside your guitar case. This will allow you to identify when your guitar is being exposed to too much humidity or unusually dry conditions, and will allow you to plan accordingly.
If your environment is too dry...
To raise the humidity levels where your instrument is kept you will need to use a humidifier.
This humidifier is compact and intended to be kept inside your guitar case. All you need to do is fill it with water (it doesn't take much) and this humidifier is designed to be water tight so as not to damage your instrument, but it is also made from material that allows water vapour to pass through, increasing the humidity level inside your guitar case. I, like many guitar players I know, keep one of these in my guitar case.
The D'Addario 2 way humidifier is a pack you can leave inside your guitar case that will not only humidify your guitar case, but if the humidity levels inside your case become too high, this product will absorb humidity and maintain the level between 40% to 50%.
If you are not in the habit of keeping your guitars in their cases, I highly recommend you keep a humidifier in the room where your guitars are kept. I have this exact humidifier kept in my home office right next to my guitars, and it has been a game changer during the winter.
If your environment is too humid...
To lower the humidity levels of your environment, try using
Silica gel packs placed inside your guitar case. These are designed to absorb moisture and protect products from damage due to humidity. Keeping one of these inside your guitar case will reduce humidity levels.
I know I already mentioned this one, but the D'Addario 2 way humidifier is meant to lower humidity levels that are above 50%. If you are looking to reduce humidity levels, this should do the trick.
If you are not in the habit of keeping your guitars in the case, air conditioning units will decrease humidity and running an air conditioner will help to keep humidity levels from becoming too high. Unfortunately, I don't have enough personal experience with air conditioning units to recommend something that would be effective for this use.
Thank you as always for checking out my thoughts on this subject. Please feel free to reach out with any comments or concerns, and thank you for making me a super small part of your journey with the guitar, its something I don't take for granted! :)