Humidity: How It Can Create Serious Problems!

autumnAs winter is now in full swing in the northern hemisphere, the time has come to take a closer look at how you store your precious, cherished instruments. As the cold creeps into our homes we tend to close down all windows and pump up the central heating. Unfortunately, many players tend to forget some basic precautions to safeguard their guitars from harm, sending many guys on their way to a guitar tech or luthier during the winter! I want to take a moment to examine the most often made mistakes, what that could lead to as well as some preventive measures! The biggest enemy of our guitars is moisture. Too much can cause the wood fibers to swell, which in turn may cause the fretboard to exhibit some bumps or the top of your (semi) hollowbody or acoustic guitar to bulge upwards causing the bridge to come under strains and tensions it wasn’t designed to handle. But if the air gets drier, the woods, even though they are often finished with some kind of lacquer, will evaporate some of their moisture. When the cells of the timber lose moisture they tend to shrivel a bit, causing fretboards to shrink, tops to shrink and in turn tear from the sides and their braces or maybe even crack! Too much moisture in your home isn’t good – that goes without saying – but it’s less bad than having the air too dry!

A top, cracked due to bad storage.

A top, cracked due to bad storage.

But what causes these troubles? Why is the wood so fragile and prone to deforming with a change in relative humidity? In part, the answer lies in the structure of wood itself. Wood consists of cells, little pockets of cellulose fiber filled with water and resin. As the water evaporates the resin stays. Huge amounts of the resin can be ‘washed’ out and later the wood is dried to achieve a relative humidity. This can be done by letting it hang out in the open air (assuming the area is relatively dry), or in a kiln. The latter is of course much faster! But as the surrounding climate may see a rise in relative humidity, the wood itself will absorb moisture, due to its inherent nature! As it absorbs water it will slightly deform.

You can’t totally banish the level of absorption, but you can try to control it. By creating a stable, humid environment when the guitar is being built, it’s likely that the guitar will lose a bit of moisture over time. It’s the excess amount of water that might be lost or gained that you should be worried about. Gaining moisture isn’t that common, actually, since so many luthier shops already run their relative humidity at somewhere around 65% and many areas in the world are drier than that! No, it’s the excess amount of losing that will cause issues in the long run. Your fretboard will shrink, making the fret ends stick out. In turn, you’re hands will be torn open which may lead you to retire an otherwise perfectly fine guitar. You may see some weather-checking in the finish and even that is fine in a way. Acoustic guitars may experience much more problems due to changes in relative humidity. For example, the top may expand or contract and if you’re out of luck, the top will simply split along the grain!

acoustic-guitar-bridge-pulling-up

The bridge is curling up because the top is shrinking!

Since the issue isn’t really a summer thing: you’re more likely to open up windows in the summer, so the indoor climate can be more like the outside climate. In the winter, you often run a heating system, causing the air to go drier and drier with all of the aforementioned tribulations. So, the solution? That’s actually quite simple. Get a humidity gauge and a humidifier! A humidity gauge won’t set you back enormous amounts and a humidifier is never a bad idea. For starters, you will see that your body will thank you for having a humidifier in your house during the winter! If the air is more moist, your nose and throat will be more moist as well which in turn are less likely to inflame during the winter! You just have to keep an eye on the humidity gauge and run the humidifier accordingly. If it changes approximately 10% over the course of a day, that’s a lot and never a wise move! But 10% gradually over a week, with temperatures fluctuating within a margin of 5 degrees, I’d be very much surprised to see a lot of ‘winter patients’ coming in this winter!

About Orpheo

Orpheo is a long-time member of the Seymour Duncan forum with an interest in the technical side of luthery and pickups and plays jazz, blues, rock and metal on predominantly carved top single cutaway guitars.
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  • Campbell

    Just play the bloody thing , before it gets stuffed by nature ..
    All this worry about temp and humidity is crazy , as long as you don’t leave your guitar in the boot of your car in summer or leave it outside in the rain it should last for ages , as far as cosmetics go you will have to ask SRV about that. :)

    • Rick Martin

      Playing the bloody thing won’t stop any effects from humidity. Look after your instrument, and it will usually last a very long time.

      I’ve seen acoustic tops cracked by drying out – completely preventable.