Humidity and Ukuleles: What You Need to Know

BY ANDREW KITAKIS

In working with the ukulele community for the last 20 years, I have witnessed the joy and fulfillment many friends have found when they find that special ukulele. Those of us who are musically sensitive and find self-expression through our music can develop a strong bond with our most loved instruments.

“It’s really the equivalent to our cultural dating tradition which allows us to find that perfect mate,” says my friend Jerry Turney. I couldn’t agree more, and I love my job in helping people find their musical match. I regularly get emails and calls from customers who are overjoyed with their purchase. Occasionally, though, we get an email from a distressed customer whose cherished ukulele has developed problems or even cracked. While we do our best to help, many times these issues are a direct result of the player not being aware of humidity’s effect on their ukulele. So let’s look closer at why this problem exists and what we need to know to make sure our instruments stay healthy.

The Basics of Humidity and Wood Instruments

Wood always contains moisture and it swells or shrinks as its moisture content changes. To keep it healthy and playable, a solid-wood ukulele needs to be kept somewhere between 40 and 60 percent relative humidity (RH). Doing so keeps the thin panels of wood from fluctuating too much. [Editor’s note: While laminated instruments are less vulnerable to humidity changes, they should still be cared for with the same attention.]

If the humidity gets higher than 60 percent, the wood will swell, causing higher action, quick corrosion of your frets, and in extreme cases, loosened bridges or braces. If the humidity falls below 40 percent, the wood will shrink, causing even worse problems, such as a top or back sinking or separating from the sides; loose braces; the action becoming lower and creating fret buzz; protruding frets, causing them to become sharp, because metal does not shrink like wood; binding that pulls away from the body wood; and cracks. Since the vast majority of issues come from excessive dryness, we’ll focus on some of the problems that come from an instrument in need of higher humidity.

Many parts of the world are very dry. In the United States, portions of Arizona, Nevada, Oregon, Colorado, Wyoming, and California are classified as desert regions and ukulele owners in these areas have learned (sometimes the hard way) just how important it is to raise the humidity level where they store their ukuleles.

Jerry Turney lives in a part of Arizona where the relative humidity is usually under 10 percent. He has a process that has successfully cared for his ukuleles for many years. When not playing, he keeps them in their case with one Oasis humidifier hanging in the soundhole and one at the headstock area.

“The most important factor is consistency,” he notes. “Every Friday afternoon, I religiously refill the humidifiers in all of the cases. I don’t like it to get below half-full.”

Another budget solution for maintaining humidity is to make your own humidifier using a travel soap-case and a sponge. Jerry suggests drilling holes in the top of the case and placing a sponge, “not so wet that they can leak all over, but moist,” and leaving it in the case. This might seem like a lot to get and keep up with, but if you care about your instruments and live in a dry climate, you have to do something like this, especially if you don’t have a room or house humidifier.

Staying in Front of the Problem

Customers in desert-type areas know they have to address this issue, but many problems come from seasonal environments where cold winters make people heat their homes. In these areas, the weather report can make the humidity seem fine, but from your instrument’s perspective it’s actually not. This is where it’s important to understand the difference between absolute humidity and relative humidity.

The air around us contains a certain amount of water vapor. The amount of water vapor any mass of air can hold depends on the temperature of that air: The warmer the air, the more water it can hold. What this means is that air with a low relative humidity is dry air that could hold much more moisture relative to the maximum amount of water it could hold at the same temperature. So, for example, at 32 degrees Fahrenheit, a cubic foot of air can hold 5 grams of water. If that air is at 100 percent relative humidity and you bring it into your house and heat it to 77 degrees Fahrenheit, the relative humidity then falls, drastically, to 23 percent. (When heated to 77 degrees, that same cubic foot of air can now hold 22 grams of water.) Relative humidity is what affects your instrument, and as you can see by our example of heating cool air, most houses in the wintertime get well below dangerous levels when heaters warm up air.

One of the best ways to stay on top of humidity readings is by using a digital hygrometer. A hygrometer is a device that measures the moisture content of the atmosphere, be it in your living room or the inside of your ukulele case. They’re available at many hardware stores or online and are reliable for staying on top of humidity levels, but they require you to open the case to check readings. There’s a new way to stay informed of the humidity inside your ukulele cases at any given time: D’Addario sells a digital hygrometer called Humiditrak that uses an app to let you check your levels from your phone or computer. It also sends you a notification if it gets below or above certain levels.

Though there are many instrument humidifiers on the market to choose from, you may also want to consider using room humidifiers in your home. Not only is low humidity hard on ukuleles, it’s also hard on our bodies. Raising humidity levels to 45 percent greatly reduces risk of infection and airborne viruses. By maintaining this comfortable level of humidity, you can also improve your sinuses, your skin, and, as a side benefit, you can spend less on your heating bills by making your house feel warmer at a lower temperature.

Conversely, you may want to take humidity out of the air in very humid environments, like we have here in Hawaii. One way is with an air conditioner, which uses dry air, but you should monitor the humidity levels because they can easily get too low if you’re using one all the time. Dehumidifiers can also help reduce the humidity and they are relatively inexpensive. For players who are traveling and encountering a variety of humidity changes, D’Addario also makes a two-way humidity system for your case that will add or reduce humidity as necessary.

Hopefully, you’re now more aware of the humidity issues facing your ukulele and you can take the necessary measures to ensure your ukulele is a healthy and happy musical companion for many more years. Aloha!

Andrew Kitakis is a former luthier who lives on Oahu and is the founder of Hawaii Music Supply and theukulelesite.com.

This article originally appeared in the Spring 2017 issue of Ukulele. This web post was updated in August 2024.