Drastic swings in humidity can damage your acoustic instrument. Thankfully, there are affordable solutions when it comes to guitar care and humidity control.
Of the 1.36 million acoustic guitars purchased in the U.S. in 2013, it’s likely that very few of the guitarists who purchased their instruments got the scoop on one of the most critical aspects guitar care: the importance of monitoring both temperature and humidity in the environment surrounding the instrument. Extremes (low or high) in humidity can deform your acoustic instrument literally overnight. Not only acoustic guitars, but mandolins, fiddles, ukuleles, reeds or any other instrument crafted from wood is susceptible to a variety of problems that can arise from poor climate control.
Just how serious a risk are extreme climate conditions to your instrument’s well being? In a 2009 article penned for Premier Guitar magazine, Bob Taylor, co-founder and president of Taylor Guitars, stated that, “At one time, probably 70% of the repairs performed in our service center could have been avoided if the guitar had not been exposed to humidity extremes.” So let’s look at the basic information you’ll need to keep your guitar or other wooden instrument healthy.
Understanding relative humidity
A quality guitar is manufactured under very specific temperature and humidity limits. Martin Guitars are made in a factory where the relative humidity (RH) is maintained between 45-55 percent and temperature between 72-77 degrees Fahrenheit. This is to ensure that while the many different parts of the guitar are manufactured and assembled, the wood remains stable. This is important because wood is a porous material, which means that if the relative humidity (aka moisture content) in the surrounding environment goes up rapidly, the wood in your guitar is likely to expand and swell.
Conversely, if the humidity goes down rapidly, some portions of the guitar are likely to shrink faster than others, potentially causing cracks or open joints where two parts are touching. Basically, the further away your guitar’s environment gets from the range mentioned above, the more risk of damage there is. This is particularly true if your instrument is subjected to a very sudden change in humidity and temperature, such as when you leave your instrument in a car while temperatures are freezing with relatively low humidity, then bring the guitar into a 75-degree heated club with condensation dripping down the windows behind the bandstand. Also, if your instrument spends time under hot stage lights, you will need to pay special attention to the humidity as the heat generated tends to quickly dry out the instrument.
When it comes to guitar care, the easiest and most reliable way to measure humidity is to purchase a digital hygrometer, and keep it in your instrument case. There are a range of digital hygrometers (available for $10-40 at your local music store, on Amazon, or Radio Shack). The reason you want to keep it in your instrument case is to keep an eye out for sudden swings in humidity. When you do have to go through a radical humidity change, keeping your guitar in a tightly sealed instrument case for minutes or a few hours allows it to get used to its new surroundings gradually. Simply put, “humidity is easier to control in a small space,” according to Martin & Co.’s Care and Feeding Guide.
It’s also good to find out what the normal humidity is in your hometown as that can give you a clue on whether or not your instrument is likely to be at risk of becoming too dry or swelling up from too much moisture. Arizona, Nevada, Colorado, Utah, and parts of California experience low humidity nearly year round. If you live in Florida, Hawaii, or Seattle, then the opposite is more likely the case.
Additionally, during winter months, especially in colder regions, you are likely to significantly lower the RH every time you entire a heated space like your home, an office or a venue. If you get in the habit of peeking at your hygrometer each time you take out your instrument, you can keep an eye on the relative humidity wherever you are and take any necessary precautions (which we’ll cover below) to make sure your instrument is safe and ready to play at its best.
Symptoms of a dry guitar
While it’s possible that too much RH can cause your guitar to swell, it’s a much more common problem for your guitar to have excessive dryness (low RH). What are some of the symptoms? What you don’t know can hurt your instrument. Back when I was playing in a band every night, my group did an acoustic set that featured me on mandolin. At the time, I had a beautiful old Gibson A-4 mandolin and nearly every night, especially in winter, I’d notice cracks in the back of the instrument opening and the action became so low it was nearly unplayable and hard to keep in tune. Unfortunately, I never understood that the radical shift in RH from outside to the club’s interior and the hot lights were drying out my A-4. I finally traded the instrument so it could have a more stable environment and not be constantly in the shop for repairs, replacing it with a more stable Washburn. Had I monitored the RH and used some the methods outlined below, I could have stabilized that instrument and kept it in good playing condition.
Guitars subjected to low RH (usually 40% or lower) may exhibit some or all of these symptoms: lower than normal action (strings very close to fret board); sharp fret ends extending beyond the end of the fret board; and a sunken top across the soundboard between bridge and fingerboard (lowering the bridge at the same time). For musicians who don’t understand the nature of wooden instruments and RH impact, they may take their instrument into a repair shop complaining of excessive buzzing in the higher register, neck bowing, or a hump in the freeboard where the neck joins the body. These are classic symptoms of an instrument that has simply “dried out.” Restoring the RH to 45-55% will literally heal nearly all these problems, if they are caught in time.
An ounce of prevention
In the latter part of my performing career, I learned to keep a tube style humidifier in the hard shell case of my Martin D-18. I checked it weekly and made sure it stayed moist. The need to have my neck adjusted each year, disappeared, saving me that expense. The humidifier cost about $10.
Today, however, maintaining the RH in your instrument case has gotten a lot easier and more reliable than remembering to check your tube humidifier and re-wetting its sponge. There are now two-way humidifiers, meaning it can either release or absorb moisture to consistently maintain a predetermined RH level that is noted on the packets. (Unlike my old tube humidifier, which could only add moisture). The contents of these two-way humidifiers are just salt and pure water, so only water vapor is released or absorbed. The leading firm providing these “two way” systems is Boveda, out of Minneapolis. Boveda’s “B49” packs automatically detect and correct the RH in your case and last an average of 2-5 months, depending on the climate, adding or removing moisture as needed. So they’ll maintain a precise 49% RH in your case no matter where you travel or what changes happen around your instrument. Normally, you’ll place one in a pouch under the headstock and two in a pouch that hangs down over the strings and into the sound hole cavity.
It’s time for a new set when the packets have very little softness left to them. When you first get the two-way humidifiers, you may need to change them sooner because the interior of most guitar cases that have not had any humidity control is very dry. One solution to this is Boveda’s special 72 RH packets that will help “season” your guitar case if you are just getting started with humidity control. Wooden guitar cases have nearly twice as much wood as your guitar, and all that wood needs to get back to a relatively neutral (45-55%) RH. According to the Boveda team, you simply get four of the 72 RH packets and store them in your case for about two weeks along with your instrument since it’s likely overly dry, too. Once you’ve completed the seasoning process, you can rely on the normal 49 RH packets to maintain optimum humidity in your case.
Five Tips to Keep Your Instrument Healthy
Now that you know the importance of monitoring your instrument’s environment to balance the relative humidity, here are five tips that Bob Taylor shared in the previously mentioned Premier Guitar article that make good sense to follow.
- Store your guitars in their cases. The case will shelter your guitar through many extreme conditions, even though it’s more convenient to have them readily at hand. A stand or wall hanger is not the best place to store them unless you humidify your whole house.
- Use a humidifier in your guitar case during cold months or at all times if you live in a dry climate.
- Keep a digital hygrometer in your case and look for 40-50% RH readings.
- Learn to “read” your guitar by noticing sharp frets on any guitar – acoustic or electric – and low action on your acoustic. These are signs of drying wood. When you see this, put the guitar in its case and give it a dose of humidity. The sharp frets will go away.
- If you choose not to store your guitar in its case, at least put it in there for one week a month with a humidifier. Think of it as a week at the spa.
Learning to protect your instrument from the ravages of low humidity only requires a small investment of time and money and the payback will help keep your instruments in tip top shape for life.
“Using a Guitar Humidifier” (Taylor Guitar Tech Sheet)
“Symptoms of a Dry Guitar” (Taylor Guitar Tech Sheet)
Bob Taylor demonstrating the two-way humidifier
These are the Planet Waves two-way humidifier version called “Humidipack.” They work the same way as the Boveda products mentioned in the story.
Keith Hatschek is a regular contributor to Disc Makers Echoes blog and directs the Music Management Program at University of the Pacific. He’s also written two music industry books, How to Get a Job in the Music Industry and The Golden Moment: Recording Secrets from the Pros.
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