Subsequently it stands to reason that this treatise should be entitled "how to avoid killing your guitar" as this more accurately reflects the emotion behind the measures that we as musicians need to take in order to protect our beloved instruments. And in lieu of the fact that there are a number of ways to annihilate a guitar without even raising a single finger or moving our recumbent and occasionally indolent bodies out of the cushy-comfort of our lazy-boy loungers, it is of the utmost importance that we maintain a certain semblance of awareness concerning the day-to-day care of our guitars. In fact one of the biggest threats is as predominant and ubiquitous as the air we breathe and in fact, it is the air we breathe.
Humidity, or the lack thereof, can be the most destructive force to the well-being of any instrument particularly if it's composed of wood. Subsequently it's imperative to the life and longevity of the guitar that you create an environment that is suitable and appropriate for the instrument, especially if you live in an overly dry or humid climate. The expression "relative humidity" is used to describe the percentage of moisture in the air relative to the maximum amount of moisture that could be present, and this percentile can vary drastically from climate to climate, place to place. It stands to reason that desert regions will have lower levels of humidity while coastal regions will have higher levels but there are other factors that guitar owners need to keep in mind as well concerning the relative humidity in their places of residence. Humidity is typically higher in areas near to the equator but can be substantially less in regions falling in low and high latitudes. Also, those who are prone to crank the heat up in wintertime (and do not have in-home humidification devices), or run the air conditioning in the heat of summer may also be unwittingly robbing the air of precious moisture that can also cause adverse and sometimes astronomical and irreversible damage to your guitars.
Inevitably, it's of the utmost importance that we measure the humidity in our homes to maintain some reasonable semblance of awareness of what the measure of relative humidity is that surrounds us and our instruments, so that we can take the steps necessary to mitigate the potential problem. The accepted range of humidity is 35% at the low end and 70% at the high end or simply stated, below 35% and you need to increase the relative humidity and above 70% you should decrease the humidity. Some manufacturers, including Martin, claim that anywhere between 45-55% is a great range of humidity for the health of your guitar. Keep in mind though that this range is not considered a cut-and-dried issue as there are numerous factors (that we'll discuss shortly) that can affect whether or not your particular guitar will become damaged above or below these levels. There are simple and inexpensive tools that can help you to keep an eye on humidity though and help to protract the life of your instrument. You can measure the relative humidity in your home and/or in your guitar case with the use of a hygrometer, an instrument widely used in scientific circles to measure humidity in a number of different applications, including guitar care. New hygrometers can be acquired for anywhere between about $8 for an analog display and $25 for a deluxe digital hygrometer with a guitar humidifier built in. Keep in mind that the lesser expensive models are notoriously inaccurate though so you may want to spend the paltry few extra dollars to get the digital model. Considering that you could render your valuable instrument useless by not paying attention to the relative humidity, it's really not a whole lot of money to spend, is it?
Exposure time is one of the primary factors that can affect whether or not adverse levels of humidity might damage your guitar and the longer your precious baby is exposed to the elements the more likely there may be unfavorable circumstances. If you're a performer and you know that your guitars will be exposed to either drastically low or high levels of humidity for the period of time that you'll be on stage, then be assured that likely as not your guitars will not suffer (although many players keep their expensive guitars cased whenever they're not being played simply for safety's sake). Yes, rapid changes in humidity are not healthy for the guitar in general but the shorter exposure time should help to moderate the potential problems. If you're a player that likes to have his or her ax nearby at home, perhaps out in the open on a stand (for example) so that any passing inclination to strum or any potential brilliant song idea does not go unheeded-undeveloped-forgotten, you may be opening yourself up for some potential problems down the road. Despite the fact that it's much more convenient and much more conducive to the creative process, keeping a guitar out in the open may be detrimental to the health of your guitar especially in regions with extremely low or high levels of humidity.
Temperature is another point of consideration when considering the long-term health of your instrument. Recommended temperatures for guitar health fall in the range of 72 to 77 degrees Fahrenheit, although a couple of degrees either way shouldn't have an adverse affect on the guitar. Monitoring the temperature is important but equally as important (if not more so) are potential rapid changes in temperature. Keeping your fine instrument near a fireplace, a sunny window or a heating vent are all poor choices for storage and should be avoided due to the potential for rapid changes in temperature. If the guitar is accidentally left in a spot where the temperature reaches inordinately low temperatures, leave the guitar in its case while you restore it to ideal temperatures and allow the instrument to warm gradually. I cannot emphasize this enough: unfavorable conditions are unhealthy for the guitar but rapidly changing unfavorable conditions can be catastrophic!
Another factor that can be a determinant in whether the weather and the relative humidity may or may not damage your guitar is the type of finishing process that the guitar underwent before you purchased it. The quality and quantity of the materials employed, as well as the quality of workmanship involved can have a profound effect on how your particular guitar is able to withstand the elements. There is a fairly wide range of products used to finish the exterior of a guitar ranging from inexpensive polyurethanes to more expensive Nitrocellulose finishes. There are two varieties of polyurethane treatments, solvent based and water-based and each have their advantages and disadvantages. Solvent based poly finishes are considered the old-school type of treatment and are characterized by a chemical reaction that occurs during the curing process. The result is a strong polymer bond that cannot be broken down and dissolved easily, and this bond creates an incredibly strong protective coating that can help to decrease any potential damage to the guitar from the environment. One of the down sides of this particular treatment though is its level of toxicity and potentially hazardous byproducts, and because of this the use of these products has diminished over time in the United States. And although polyurethane finishes are durable, they also have a tendency to restrict wood's natural ability to wick moisture away from the wood, which can cause other problems to the instrument in the long run. Water-based poly treatments are not as durable as solvent based products but are much easier to handle and less toxic as well. Nitrocellulose is an amazing substance (a.k.a gun cotton in low-order explosives) that has been applied in various areas including explosives and film, and is also currently used as a superlative finish on guitars. Despite its unstable nature, Nitro is an remarkable substance that has been utilized as a guitar sealant for decades due to the fact that a series of thin coatings can be applied that is effective yet still allows the guitar a relatively natural exchange of moisture between the wood and the air.
So you see that there is a trade off: polyurethane finishes will help your guitar to fend off potential problems resulting from changes in humidity and temperature, but inevitably may cause problems in not allowing moisture to escape; nitrocellulose finishes, on the other hand, are not as durable but are more conducive to the natural aging process (and sound production as well) of the guitar.
Potential problems that can develop as a result of an overly dry and desiccate environment, or rapidly drying environment, include uneven shrinkage in various parts of the guitar. This incongruous contraction of the wood can cause cracks in the finish, joints and even glue joint failure. Guitar dehydration can also cause noticeable changes to the sound of the guitar itself causing a thinning brittle sound, or what some players call "plinky" sound. As humidity increases beyond certain levels, wood tends to absorb harmful levels of moisture from the surrounding air and various parts of the guitar are prone to swelling. Gradual increases in humidity don't seem to produce the adverse affects that rapid changes do, but high humidity combined with high temperatures can once again cause weakened glue joints and even weaknesses and subsequent detachment of the bridge from the face of the guitar. High humidity can also manifest itself in the sound of the guitar and can obscure projection, muddy tone and dampen volume. This is, in essence, the manifestation of the environment's benign but nonetheless efficacious efforts at killing your guitar, come to fruition.
Is there a guitar player, strummer, picker, lover, shredder or even distant but ardent admirer who would participate, either knowingly or not, in the demise of an instrument so brilliantly designed, fashioned, rendered? Haven't we gained a certain semblance of rationality and reason, a heightened sense of awareness concerning the value of an instrument so beloved that to provide the proper nourishment and create the most fruitful environment for it is not even a simple matter of choice, but rather a moral imperative that we as musicians are compelled from within to fulfill?