The most important factor in protecting a solid wood acoustic guitar is to understand the effect of temperature and humidity on it. The best way for you to be able to protect your guitar from damage is to understand what factors affect it and how best to control these factors.
In general, the conditions which humans find most comfortable are the best for a solid wood instrument. Limiting both low and high humidity, as well as drastic swings from one extreme to the other, is one of the single most important things you can do to get longevity, playability, and balanced sound from your instrument.
By understanding what you are measuring, why it's important to your instrument's health, and how to properly control it you can begin the first step in a critical aspect of owning a fine instrument. Like a fine wine, older instruments that age properly tend to sound the best. Hence the reason why vintage instruments are so highly sought after.
A hygrometer measures the amount of Relative Humidity, or RH, in the air. RH is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. RH depends on temperature and the pressure of the system of interest. It requires less water vapor to attain high relative humidity at low temperatures; more water vapor is required to attain high relative humidity in warm or hot air.
In other words, RH is the amount of moisture in the air relative to the amount of moisture the air can hold before it reaches the saturation point. As the temperature of the air rises, so does its ability to hold additional water.
RH is normally expressed as a percentage; a higher percentage means that the air–water mixture is more humid.
In cold climates, the outdoor temperature causes lower capacity for water vapor to flow about. Therefore although it may be snowing and at high humidity relative to its temperature outdoors, once that air comes into a building and heats up its new RH is very low. This results in very dry air, which is a hostile environment for a guitar and the primary reason we created our patented ClimaStand, ClimaCases, and ClimaCabs.
The following conditions are common when heating season begins:
1.) As the temperature increases without an additional source of moisture in the house the RH drops.
2.) The air you are starting with before you heat it is very cold, meaning that it is carrying very little moisture even when the RH is very high, such as in a snowstorm. Because cold air has a very low saturation level, it will carry very little moisture. Even if the RH is high when it is cold, by the time that air is warmed up to 75 degrees, the RH will be extremely low. The saturation point of air at higher temperatures is so much higher, that the RH will be very low, unless significant moisture is added to that air.
3.) As you force more heat into your home this further dries out the air. The result is that if you live in a dry area such as the notorious Rocky Mountains, or in Acoustic Remedy's home state of Wisconsin, you will have to be careful to protect your guitar from low humidity damage.
In general, extreme low or high humidity have equally detrimental effects on a wooden instrument. Also, generally speaking, low humidity is the most common culprit of damage. This could be because more environments experience low humidity than those with extreme high humidity or it could be the result of the common humidification devices being difficult to maintain a consistent regimen.
The recommended RH for guitars is 45 – 55%; however, 40-60% is generally considered acceptable. This is not a subjective range of one luthier, but rather a consensus across the board from every luthier on the planet.
From Taylor guitars website:
"Proper hydration is vital to the performance of wood products like guitars, whose stored moisture can be robbed by dry, thirsty air. In fact, extended exposure to dry conditions poses one of the biggest threats to a guitar’s health. As a guitar loses moisture, the wood shrinks, which not only compromises the playability and sound of the instrument, but can also lead to cracking and other damage. If you notice your guitar’s action getting low and buzzy, or feel your frets protruding as you move up and down the neck, it’s likely a symptom of a dry guitar. Even if you don’t currently see or feel these symptoms, your guitar could still be dry. Maintaining proper guitar humidity levels will help you keep your guitar in top playing condition."
There is also some really good information from our friends at Santa Cruz Guitar Company. Make sure to click the header for Temperature and Humidity.
Low RH Effects
Below about 40% is considered low RH and can cause cracking in both the wood and lacquer. The top will drop, lowering action to the degree that the strings will buzz, sometimes to the degree that it becomes unplayable. Lacquer checks will develop along the purflings, bindings, and at glue seams. The fingerboard will shrink, leaving the fret ends protruding beyond the edge of the binding. This makes the instrument uncomfortable to play. Usually the first symptom to develop will be a slight dropping of the top and lower action, followed by the possibility that a hairline crack may develop along the bridge pin holes. This is an excellent early warning symptom. It is easy to fix and it lets you know that you are headed for trouble if the humidity problems continue.
High RH Effects
65% and above is considered high RH and causes the top to rise, making action high or unplayable. It can cause lacquer to check, impressions of the braces may appear on the top and puckers may appear where the top is glued to the internal structure of the guitar, such as at bridges, braces, head blocks, and tail blocks. It also restricts movement of the top resulting in a guitar that may sound tight or restricted.
If your problem is high humidity, it will be harder to deal with, but it is also is a safer condition. Air conditioning will really help you keep the humidity at a reasonable level. As the temperature lowers, so does the saturation point of the air, water will condense, and the RH will decrease. Do not use a swamp cooler in an already hot, humid area, as it will almost certainly spell out problems for your guitar by causing high humidity conditions.
Rapidly changing humidity is the most damaging condition you can expose your guitar to. Having a guitar go from an environment of 75-85% humidity to 30-35% immediately could easily cause severe damage to an instrument.
Additional issues occur within the home which can make RH control difficult to manage for both human comfort and the health of your guitars. For example, unless you live in an arid climate, periods of high humidity create a myriad of problems for structures and people. Symptoms of high humidity would include:
These conditions will also hold true in climates that go through seasonal temperature swings, which is really a majority of North America. When the temperature drops, we turn on the furnace and simultaneously the humidity levels inside the house drop. The following chart shows just how low the RH can get inside a house at typical winter temperatures.
| Outside Temperature | Outside Relative Humidity | Indoor Humidity with Indoor Temp @ 72 degrees F |
| -10 degrees F | 40% | 1% |
| 60% | 2% | |
| 80% | 2% | |
| 0 degrees F | 40% | 2% |
| 60% | 2% | |
| 80% | 5% | |
| 10 degrees F | 40% | 4% |
| 60% | 5% | |
| 80% | 7% | |
| 20 degrees F | 40% | 6% |
| 60% | 8% | |
| 80% | 11% | |
| 30 degrees F | 40% | 8% |
| 60% | 13% | |
| 80% | 17% |
We’ve all felt the depleting effects of dry conditions on our bodies. Think of a long flight spent in an airplane cabin, where the humidity can drop below 15 percent. Or the parched interior of a home being heated during cold winter months, where the humidity can sink into the single digits. Our eyes and skin get dry, we get thirsty, and in extreme cases we might even get a headache or a nosebleed. Therefore, it's no surprise that most people attempt to humidify their homes to make it more comfortable to live in. When we start to introduce humidity to combat the dry air, we wind up with the same undesirable high humidity issues listed above.
A common used technique is to humidify a room where guitars are stored using a single room humidifiers. Keeping the air in the 45-55% range over the course of a winter is more than most homes can handle. Water or ice will appear on windows and it can migrate into walls and attic cavities. After a few winter seasons, homes may begin to experience molding, rotting, and deterioration. Eventually homeowners will have to pay for repairs and replacements, but it can also result in poor health.
Another important topic to consider is that most people like to vacation from the colder climates during the winter. During these times, you cannot simply just run your room humidifier dry and hope for the best.
By utilizing our highly effective humidified ClimaStands, ClimaCases, and ClimaCabs you can expect to minimize fluctuations in humidity and temperature with the world's simplest system.
In general, our approach is that without a sealed environment it's an uphill battle to control the humidity levels inside the humidor. Our patent revolves around creating an airtight environment. We accomplish this with a combination of a highly durable neoprene gasket and a mechanism to pull the door tight to the gasket thereby creating a micro-climate inside. This mechanism varies from the ClimaStand/ClimaCase utilizing a set of spring loaded latches to the ClimaCabs which utilize several neodymium magnets to accomplish the task.
From there we employ the Boveda Two-Way Humidification packets which automatically release or absorb moisture to keep the RH at the set level of the packet. They make three primary packet types - 49%, 49% HA (High Absorption), and 72% Seasoning packet. The 49% is great for most scenarios, the 49% HA can be utilized in more humid environments such as the tropics, and the 72% can fast track humidification if your instrument is really dried out to begin with.
We've put an exceptional amount of research and development to bring you the world's best instrument humidors. From that special one guitar to your entire collection, we can assist you with your mission to protect and display with a touch of class.
We invite you to explore our ClimaStands, ClimaCases, or ClimaCabs to find the product that is right for your collection.
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