Yes! That is a thing, a dangerous thing, and now is exactly the time (here in North India) when over-humidification symptoms begin to surface. Over a period of a month, I am expecting a lot of ailing guitars.
Just like an exposed acoustic guitar (not so much solid-body electrics) can lose moisture, become dehydrated and show symptoms thereof, an instrument can absorb moisture from the surroundings and get over humidified.
Also, if one notices that his/her guitar has dried out and the consequent humidification process goes too far, over humidification can happen, causing all sorts of problems, which may or may not be remedied.
The following are a few problems that come to my mind immediately. Please note that this list is far from exhaustive and there may be other problems associated with over humidification that have slipped my mind, or ones that I am yet to get acquainted with (We all learn each day, as we go)!
The Ski Jump
This is a classic symptom. If you look at the guitar sideways (as shown in my childish diagram), the fretboard tongue (from the body joint till its end) seems to take off into space for no apparent reason.
Also, if you sight down the fretboard, towards the bridge, you will notice that the bridge is invisible because it is blocked completely by the risen fretboard extension.
Not only does this give rise to fret buzzes, on a cutaway guitar, playing on the higher frets is near impossible for the strings are sitting on the fretwires here.
The remedy here is to correct the humidity content, apply a little heat and pressure.
Bellying and String Tension
Not always is the bellying in an acoustic guitar due to faulty manufacturing (crappy bracing and bridgeplate used). If it is the wet season and a belly begins to grow, it means that guitar is over humidified.
String tension acts on the top and helps the belly grow. That is one of the reasons I tell people that if it is known that an instrument will not be played for three weeks or more, loosen the strings.
As the top expands after soaking in moisture, the finish on it does not expand in the same proportion and thus the ‘shattered glass’ look.
One may notice this phenomenon growing as the instrument continues to take in moisture. On sudden exposure to moisture – moving from a dry climate to a wet one – the shattering can be quick and dramatic. It is not uncommon for the owner to go to sleep with the guitar okay and wake up with that shattered look.
This is one problem that is the hardest to send away. Besides removing the finish from the top, back and sides and redoing the guitar again, there is nothing that can be done.
Yes, people talk about painting lacquer thinners into the crevices of the ‘shatter’ but that may work if there are one or two cracks. If it’s a maze of ‘shatter’, doing each line separately while being tedious, may end up looking botched.
Yes, of course plastic (pickguard) shrinks with age, but sometimes, it is not the plastic shrinking but the wood it is stuck to, expanding (due to excess moisture). With the wood having moved, a corner or two of the pickguard comes loose, and then with time, the pickguard begins to curl.
First, the wood will need to be treated and then the pickguard needs to be taken off, heated some and then reapplied to the top.
Again like the pickguard, the neck may expand on soaking in moisture, letting go of a part of the fretboard, or the fretboard may expand letting go of the neck.
Again, excess humidity treatment and then a reglue job. If done with patience this should be a clean job leaving no trace of having been worked on.
Like the pickguard, the fretboard and the neck, when the top expands due to excessive moisture, some or all the braces are bound to come loose, evoking a strange rattle when you play the guitar.
After dehydrating the guitar a bit, all the loose braces will have to be detected and reglued.
Bridge may pull up
Also due to the top expanding, the bridge may start lifting. Generally, when it is a belly caused by humidity, it is the wings of the bridge that get loose. Given enough time and string tension, the bridge getting pulled off completely is not outside the realms of imagination.
Bridgepin holes get tighter
Over-humidification may also cause the wood on just the bridge to expand. This will cause the bridgepin holes to hold the pins even tighter, sometimes making it impossible to pull them out.
If after reducing the humidity content the bridgepin holes do not get back to their original size, reaming them is the only option.
Body comes apart/ binding comes loose
In very extreme cases, over-humidification may lead to the top and the back of the instrument to separate from the sides.
Before this happens, often, the binding around the instrument gets loose and falls away from the body.
Getting the binding to reglue correctly is a big pain in the you-know-what. There’s heating involved and if the right glue is not used, the binding will never reglue.
Some do’s and don’ts
- Humidify without string tension
When you feel your guitar is dehydrated and needs a drink of water, do give that drink but completely remove string tension. That way, even if you over humidify your guitar, at least you won’t be pulling a sure belly into it because of string tension.
- Check the humidity inside your guitar
There are small and inexpensive hygrometers (humidity reading devices) which you can drop into the soundhole of your guitar. Once there, cover the soundhole with something that will not absorb moisture and leave the set-up for at least 48 hours.
After that time, the reading that you get in the hygrometer will be the moisture content inside your guitar. With that reading, you can either hydrate or dehydrate your guitar. Your aim should be to always keep the humidity inside your guitar between the 45% – 55% range. If the reading on the hygrometer stays in that bracket for over a couple of days at least, your guitar is at optimum humidity levels.
How to reduce the moisture content inside your guitar
That, I guess, is the aim of this blogpost. All you need to do is drop in a couple of sachets of silica gel inside the soundbox and cover up the soundhole.
Silica gel sachets are those which you often find inside shoe boxes and packaging of electronic goods.
You DO NOT open the sachets, you just drop them as they are inside the guitar. For excessive humidity effects on other guitar parts, you need the drop a few in your guitar case, close it up and forget about the guitar for at least a week.
Later, check, and if needed, repeat the process.
SO…if you are buying a new guitar and the salesman tells you that you must put in silica gel, just nod and forget about it. Those ‘experts’ who tell you that silica gel is needed to keep the guitar in good shape, ask them to take a walk!
There is a little caveat to this entire blogpost: whatever you have read up to this point is primarily for solid wood guitars (If you don’t know what that is, search this blog for ‘solid wood guitars’). That is not to say that laminated wood instruments are not affected by excess humidity or the lack of it. It is just that changes will be minimal and many times, unnoticeable in laminated guitars.