Here in the UK, we’re no strangers to changeable weather. A scorching summer’s day might be followed by a downpour, and the next thing you know, it’s dry and sunny again! And while the changing temperature and humidity might cause frustration in knowing how to dress, it can also affect your acoustic guitar.
Understanding how your acoustic guitar reacts to different humidity levels can help keep your instrument in tip-top condition. With this in mind, let’s explore the best humidity levels for guitars and what to do if you notice any adverse effects.
The effects of humidity on acoustic guitars
The best humidity level for acoustic guitars is around 45% to 55%, with 60% being the top end. But what happens if you store your guitar somewhere with a significantly higher or lower humidity level?
Low humidity and acoustic guitars
If the moisture level is too low, the wood can contract, leading to cracks in your guitar’s body. This is one of the most common guitar problems I see, and it tends to be more common in the winter, particularly when you have the central heating on. While it might be keeping you toasty, it can also dry out the air, leading to guitar damage.
Along with cracks, you might notice your guitar’s seams breaking away and frets popping out. If this happens, your best bet is to speak with an experienced guitar technician who can assess the damage at the seams and reseat your frets. You can also take a look at my previous article for more guidance on uneven frets.
How high humidity affects acoustic guitars
Damage from high humidity can be as severe as issues caused by low moisture, so it’s certainly something to look out for.
When moisture levels are too high — perhaps when travelling out in the rain, performing in a different climate, or playing a festival — the wood can swell, putting pressure on the seams and joints. It can even react with the glue and cause seams to break.
If you store your guitar somewhere damp for a prolonged amount of time, it can also lead to mildew buildup. While this won’t necessarily affect the sound, it can be a visual sign of damage and is definitely worth assessing with a guitar service or setup.
Signs of a dry guitar
Aside from the visual cracks or loose frets, there are several other signs that indicate your guitar may be too dry:
A noticeable dip or sunken appearance of the guitar's top.
Fret buzz due to changes in neck relief or lowered action.
Stiff tuning pegs that are tricky to turn. This can indicate that the wood around your guitar’s headstock is shrinking.
A warped or twisted neck.
How do I know if my guitar is too humid?
Physical signs are the most obvious when it comes to high humidity. Carry out a visual inspection — can you see any warping or swelling? Are the seams intact? You may spot that the string action is slightly higher than usual — this is caused by the fingerboard wood swelling.
Another way to check if your guitar is too humid is to give it a play. If it sounds muffled or lacks clarity, it may be a sign of excess moisture.
What can I do to prevent humidity-related guitar damage?
Want to reduce the risk of cracks, warping, and loose frets? Here are my tips on keeping your acoustic guitar in great condition, come rain or shine.
Monitor humidity
The main way to protect your acoustic guitar from humidity-related damage is to keep a close eye on its moisture levels.
Try to maintain that optimum humidity level of 45% to 55% and a temperature of around 20°C. If your guitar isn’t in use for a while, make sure you store it somewhere safe, where it won’t be subject to damage from damp or arid conditions.
If you’re concerned about low humidity — for example, if you need to keep your guitar in a room where you know the radiators will be on frequently — consider using a humidity cage and placing it in the sound hole. This will help balance those all-important moisture levels.
In contrast, if you’re in for a very wet winter (as a guitar technician in Cardiff, I know this well!), it can be wise to consider investing in a dehumidifier to keep your space at a good humidity level.
Know your guitar’s finish
It’s also worth recognising your guitar’s finish type and how this affects its susceptibility to changing humidity levels. A polyurethane or nitrocellulose lacquer finish will give your guitar a little extra protection from exterior humidity. However, if your sound hole is uncovered, this can still be an entry point for moisture.
Consider a guitar case humidity gauge
Many people ask whether a guitar case can protect your instrument from humidity damage. To a degree, yes. Keeping your guitar in a case can shield it somewhat from changing temperatures, especially when compared with hanging your instrument on the wall next to a radiator or propping it up next to a window.
However, you still need to keep an eye on the space’s humidity level and how it’s affecting your acoustic guitar.
I recommend adding a hygrometer (humidity gauge) to your guitar case so you can monitor any changes and
Treat the fingerboard with oil
Do you have a hardwood acoustic guitar? Materials such as rosewood and pau ferro can really benefit from a layer of oil. By applying lemon oil to your guitar’s fingerboard, you can condition and protect the wood, helping to maintain ideal moisture levels throughout the year.
Get a guitar service
If you're unsure about the humidity level of your guitar, you can always take it to a guitar technician for a checkup.
An experienced guitar tech will be able to give your guitar a full service and setup to make sure it’s in the best shape for the current humidity levels. They can also recommend the best storage conditions for your guitar, based on the local climate.
Plus, if any damage has occurred, a guitar technician can work out the best way to repair it and get your acoustic guitar looking and sounding its best.
Need a guitar technician in Cardiff? Contact Alchemy Instruments
If you have any concerns over your acoustic guitar’s humidity or simply want a guitar setup to ensure your instrument is playing as it should, please feel free to get in touch.
From fret levelling to full neck repairs, I’m always happy to take on new projects and give your guitar a bit of TLC.
Take a look at my guitar services and price list, and contact me for more details.
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