How Humidity affects your Guitar / Thursday, 25 June 2015

Written by  Alex Mew
How Humidity affects your Guitar

Your guitar is made of thin, strong pieces of solid wood. As you may already know, wood is susceptible to changes in relative humidity or extremes of temperature, and as guitar owners it's important that we all understand what that really means.

Increases in humidity will cause the wood to take on more moisture from the surrounding air thus causing the wood to expand; and decreases in humidity will result in moisture being lost from the wood and subsequently the wood shrinking.
So, rapid changes in humidity - either up or down - are to be avoided at all costs.

“But I live in a pretty temperate part of the world….”

Well, so do we.. but that doesn’t mean that we’re off the hook sadly.
You may imagine that only our desert or mountain-dwelling friends need to concern themselves about this stuff, but you would be very wrong.
If you haven’t had to deal with humidity / guitar related issues before, it’s probably down to luck rather than design.

Help me! I’m swelling up!

Rapid increases in humidity will cause the wood of your guitar to swell. As guitars are usually made of varying types of wood, the rate at which different parts of the guitar will take on moisture will vary. Although high levels of humidity will seldom cause lasting problems, when the relative humidity levels are very high for a prolonged period (and temperatures are probably very high too), you may find that the glue is weakened. This would probably be most evident around the bridge. If the glue of the bridge becomes weak, it may lift under the pressure of the pull of the strings. And no one wants that!

But, the most likely cause of major humidity problems will be a lack of moisture, otherwise known as dryness.

Help me! I’m shrinking!

Some countries or regions are naturally very dry, and if you live in one you will already be keenly aware of the implications.. But regardless of where you live, the biggest thing to grasp is the concept of relative humidity, as that affects us all.

Essentially, as temperature rises, relative humidity drops, as warm air is capable of holding more moisture than cold air.
So outside may be 10degrees (Celcius) with a relative humidity of 50%. But inside your house, when the air is warmed to 20degrees (Celcius), the relatively humidity of the air drops dramatically.. and very quickly too.
As we are guitar makers – not scientists – we’ll leave it there... but understand that the hotter your guitar is, the more moisture it will need to be happy.

Air conditioning can also be dangerous. As we have found many times during international exhibitions in large, air conditioned halls, the air can be literally sucked dry. On a number of occasions we have observed guitar’s lacquer noticeably shrinking in these environments, and have found ourselves reaching for the humidifiers.
In the same way that your skin often feels very dry and tight after a long-haul flight, the inherent moisture in a guitar’s tonewood can be sucked away in a dry, recycled air conditioned environment.

Likewise, a similar effect can be experienced in centrally heated houses during the winter. Outside, the weather will be cold, and the humidity may be low. But indoors, the temperature will be quite high.. but the relative humidity will be much lower.

Your guitar has probably experienced the above examples many times without it or you even noticing, but when the above examples reach extreme levels, all manner of unpleasant stuff can happen.

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