David's Corner

The 3 H's from Hell, Part I: Heat and Humidity

David Gage

Acoustic string basses, even more so than electric basses, are greatly affected by the 3 h's from hell; heat, humidity and handling. The string bass is a high maintenance instrument. It seems appropriate that as I write this article for the November issue, it is 98 degrees with humidity over 80 percent. When the issue hits the stands it might be freezing with less than 5 percent humidity. That's business as usual for magazines and basses. A string bass simply staying in the same town in Michigan can go through extreme humidity change over the course of a year. Unfortunately, for the string bass this change presents a dangerous problem.

As the seasons change over weeks the player can adjust and protect the bass through humidity control. When an instrument is dry, it is much more susceptible to cracking from bad handling. What happens when your instrument undergoes rapid humidity change? For example, when it is traveling in January from the moist tropics on a dry airplane to Denver Colorado where the humidity is extremely low. Certainly the feel and sound of the instrument will vary with the humidity change. A well fitting sound post will minimize this effect. But more about this later.

There are other considerations in keeping your bass healthy during climatic changes. If your bass is actually cold do not expose it to a hot and dry place all at once. Leave it in the soft case with at least two instrument humidifiers inside. There are commercially made instrument humidifiers that are simply sponges in rubber tubing intended to be inserted in the f-hole. Two of these are better than one but be sure to wring out the sponge well before inserting to avoid water damage on the inside of the instrument. These are only effective if the instrument is kept in a cover or case while the humidifier is in. Remember-cold air holds less moisture than warm air and heating systems further dry out the air. It's an excellent idea to get a good room humidifier for the room in which your bass is kept They make good ones for a lot less money than they cost a decade ago. The sonic humidifiers are effective. If you get a sponge or open reservoir mist type, make sure you clean it monthly with bleach or vinegar to avoid a bacteria buildup. Vinegar will help remove mineral deposits left by the water evaporation. It is a good combination to have both the room and individual instrument humidifiers. I have seen several basses come from South America to New York where they are literally ripped apart as they dry in the New York winter. The worst cases are the basses made of South American woods such as mahogany and rosewood as opposed to the tradition string bass woods spruce and maple. It is my feeling that wood which lives in varied climates is more impervious to climate change. When an instrument comes into my shop from years of being in a humid place, I will open all of the seams except the corner blocks so that the parts can dry and shrink without pulling the rest of the instrument apart.

Furthermore, the instrument will sound better if the humidity is not too high. A symphony orchestra will sound 25 percent louder in the same amphitheater on a crisp dry day than on a hot muggy day. The thick humid air actually mutes the orchestra by creating resistance to the vibrations traveling through. Many players find the change in sound due to humidity more distressing than the actual physical damage to the bass. When the humidity changes, the possibility of buzzing from the body emerges. Increased humidity sometimes brings with it a persistent body buzz. Optimally a bass in excellent condition should not buzz but eventually, it will. Attitude is everything; one New York recording veteran told me, "you just have to play louder than the buzz".

Generally, instruments do not crack from humidity but rather they crack from the change from wet to dry. Carved bass backs are almost always made of hardwood, which is more susceptible to cracking during water transfer. Never do major back work on a string bass during humid weather, unless stringent dehumidifying is observed. When the weather dries, the work will get stressed and will not be as stable.

With the humidity string height changes as the sound post gets tighter or looser. Strings get higher in the winter and lower in the summer. In the winter, use a room humidifier to keep the humidity at about 30-40 percent. Too humid and the CHANGE will be too much when going to a dry hall to play. The adjusters or wheels that are very commonly installed in the legs of bass bridges are intended to compensate for this string height change. Often a bass will feel tighter simply because the strings are slightly higher than that to which the player is accustomed. The fit of the sound post changes. The sound post is the dowel or stick that is located just behind the bridge between the top and back of the instrument. The sound post is crucial in dictating where and to what degree the top plate (the spruce top on which the bridge sits) vibrates. As the humidity changes, the space between the top and back changes; the more humid, more space and therefore the looser the post will get and vice versa. Because of the size of the bass (the more wood the more movement) we often recommend two different sound posts. One for winter and one for summer. This keeps the bass sounding consistent throughout the year.

My next article will cover the third 'h'-handling, including traveling safely with your bass.