Humidity and Your Instrument

"by Jean Larrivee"

Jean Larrivee
Reprinted by permission

The way you care for your instrument greatly affects its appearance, sound and the length of its life. The methods you use in caring for your guitar will vary from summer to winter, from area to area, whether you live in Los Angeles, Montreal, Europe or Japan.

Summer

Although the woods we used in your guitar’s construction are aged three to five years, after assemblage the glued joints of lining, purfling, etc., can take up to a year to stabilize. With the introduction of excess moisture, the guitar will expand unless properly cared for. Damage to the instrument may result.

Larrivee Guitars are built in a strictly controlled relative humidity from 37% to 42%, relative to 24 Celsius (75 Fahrenheit). When the relative humidity exceeds 60%, the guitar will begin to expand. Following are a few symptoms of this expansion, which you would observe:

Most commonly, the top will begin to raise (or swell), which appears as a distortion of the surface of the top. This is especially noticeable on the cutaway models. The back of the guitar will also raise (swell) and distort under these conditions, as evidenced by a depression in the back at the front and the tail blocks. The higher the relative humidity, the more noticeable the distortion becomes.

Another visible change due to excess moisture is that all glued joints, (e.g. the back, top and side joints) will appear much more noticeable. This is especially evident around the inlays. The pearl is all but impervious to changes in humidity, but the wood in which the pearl is inlaid is soft and swells with the introduction of high relative humidity. As the wood swells, you will detect a line surrounding the inlay where the moisture enters the wood.

The rise in the height of the action is one of the major problems to be observed in guitars exposed to excessive relative humidity. The more moisture, the more pronounced the height of the action becomes. This problem is especially bad in very moist climates like Florida or Japan.

The change in the action is caused by a number of forces. The excess moisture causes the top of the guitar to "belly", pushing the bridge, and the strings, upwards. The back of the guitar also expands. As it does so, it pushes the neck upwards. This has the effect of making the area between the nut and the saddle somewhat concave. The problem is then further intensified by the expansion of the ebony fingerboard which causes the frets to loosen. These frets are tight when fitted and serve the function of keeping the neck back. When they loosen due to expansion of the fretboard, the neck will also bow upwards, causing the action to increase to an even greater degree.

Please keep in mind, the finish will not stop the moisture from entering, although it might slow it down for three or four days. With longer exposure to higher relative humidity, the finish will begin to distort. This distortion in the finish on the top appears as small ridges. On the back and sides of your guitar, it will appear as though pores are sinking. As the rosewood expands, the pores enlarge causing the finish (which is impervious to humidity) to sink deeper into the pores. The finish on the mahogany of the neck will also appear to have sunk into the pores for the same reason as the back and sides.

Lastly, one more annoying effect of high relative humidity on the guitar is the loss of sound quality as the instrument distorts, coupled with a definite decrease in string life.

Happily, all of the above problems associated with exposure to high relative humidity should correct themselves when the instrument returns to the normal range of humidity: 40% to 50% relative to 24C of 75F.

There are many more serious effects of prolonged exposure to high humidity, including loosening of the brace, stretch marks in the finish, an action which stubbornly remains high and a general loss of appeal in the guitar. While these problems can usually be handled by a competent repair person, they may leave lifetime marks on the guitar. Please note, damage of this kind is not covered by warranty.

Now, for the good news. Most of the problems related to excess humidity can be avoided with some simple precautions. These are our recommendations:

Never keep your guitar in a dark cool basement during periods of high humidity. Don’t store it inside its case in such an environment as the moisture accumulates in the tight quarters of the case.

Keep your guitar out of the case. A guitar stand is a good idea as it allows the air to circulate around your guitar. If possible, it’s a good idea to keep your guitar on the second or third level of your house when the weather is warm.

Another factor, which can adversely affect your instrument in the summer time, is high temperature. When the weather is warm, never leave your guitar in the trunk or back of your car. In such locations, the build-up of heat can exceed 66C or 150F. Temperatures this high can have a devastating effect on your guitar, as heat can cause the glue joints to loosen. With the loosening of the fingerboard under these conditions, the action will become very high. Please note that this problem will not correct itself when the temperature drops back to normal, and to lower the action in this case would require a major repair job not covered by your warranty.

Spruce tops contain small resin pockets not all that visible to the eye under normal conditions. This is especially true of tight grain spruce and is more common to German Spruce than to domestic spruce. When the surrounding temperature increases dramatically, it causes these resins to expand and try to escape. Of course the only way out is through the finish causing blemishes all over the top. Although this looks disastrous, it is not particularly hard to repair. A competent repair person can correct this problem with a light sanding and polishing of the top. This kind of damage is not covered by your warranty as it is caused exclusively by careless exposure of the instrument to excessive heat.

One more problem worth mentioning here is if the guitar is exposed to bright sunlight for a period of time, a premature yellowing of the top will occur. Imagine getting a tan. This yellowing is not in itself a problem, but if there is some obstruction to the light, say the guitar strap laying across the face of the guitar, it will leave a lighter print in the shape of the obstruction which would be quite a defacement. This is one thing to keep in mind when you put your guitar down during the summer months.

I do not recommend the use of any kind of oil, silicone or wax product on the fingerboard. With constant playing the oils from your fingers are more than sufficient, and the fingerboard should not crack.

To lengthen the life of your guitar strings, simply wipe the strings down with a soft cloth after you play. When changing strings, it is a good idea in both summer and winter to go over the fret board with 000 Steel Wool, (make sure you take the precaution to not scratch the finish on top) removing all build up of oils, dirt, dust and grime. The steel wool will also serve the function of polishing the frets and fingerboard which makes them more slippery and results in a slight improvement in playability.

 

Winter

Let’s move on to the winter months when your guitar is in real peril. The villain in winter is excessively low relative humidity, i.e. lower than 40% relative to 24C or 75F. Exposure at any rate lower than 40% for any period of time will most surely result in damage.

Damage caused by dryness is much more serious than damage caused by excess humidity, and usually requires the prompt attention of a competent repair person.

The most reliable way to ascertain the relative humidity in your home is the sling psychrometer. However, the operation of one is a bit complicated for general use. A hygrometer (available at most hardware stores) will give a rough estimate of the humidity, though they are notoriously inaccurate. Still, they are better than having no idea of the fluctuations in humidity surrounding your guitar. Watch your instrument, it will tell you when it is particularly dry.

One symptom of excessive dryness is a change in the contour of the back and top. When the guitar is built the top and back are slightly arched. If the wood becomes too dry, it shrinks, and the top and back can become flat, or even concave.

The finish will also distort with low humidity (though this distortion is actually caused by the wood shrinking beneath the finish). The stable material that fills the pores of the wood will pop up as the wood shrinks around it, causing small lumps to appear in the finish. Happily, this problem should correct itself when the humidity is returned to normal levels, and you should see the flaw flatten out again.

If your guitar has inlays, you will notice that a line appears around the inlay. This line also appears around the purfling, marquetry and rosette. As the wood shrinks, it draws away from the more impervious materials of the inlay causing a slight separation. A separation in the finish will not disappear when the humidity returns to normal. This problem, fortunately, will not affect the life of the guitar or its playability.

As the fingerboard of the guitar continues to shrink due to dryness, the metal frets (which are stable) protrude from the sides of your fingerboard and can catch on clothing and even cut your hand. If this occurs, you have a definite moisture problem. While a repair person can rectify this by using a file to remove the excess, you should take action to humidify your guitar before other, more costly, problems develop.

You may also observe the center seam of the back beginning to open as the back contracts, causing the finish to separate slightly. Although this is not in itself serious, it will leave permanent marks in the finish when the humidity is restored to normal levels.

The worst problem associated with excessive dryness is cracking of the top, which can result when the guitar gets below 30% relative humidity. To repair these cracks, and subsequent damage to the finish, will require a repair person to swell the wood with humidity, glue the cracks and touch up the finish on the top. This can be a time consuming and costly repair and is not covered by your warranty.

A common wintertime complaint is string buzz resulting from too low action. Again, the problem is dryness. There are two things happening, and both are contributing to the problem. A back bow may develop in the neck caused by shrinkage of the neck and fingerboard while the metal frets remain immovable, forcing the neck back. Add this to the fact that the top will also shrink, carrying the bridge down with it, and causing even greater drop in your action. This problem intensifies as the humidity falls lower and buzzing may occur up and down the fingerboard. A small drop will occur at the 14th fret on a steel string guitar and at the 12th fret of a classical guitar. This buzzing problem should alert you to humidify your instrument.

Closely related to the shrinkage pattern of the fingerboard is the development of cracks in the top along each side of the fret board where it is glued to the top. This sort of crack usually only develops in extreme cases.

The extreme cold of winter in some climates also poses a danger to your guitar. Extreme cold is mainly detrimental to the finish of your guitar and varnish checking (small cracks in the varnish) is common where temperatures drop below the freezing point. While the finish used on today’s Larrivee guitars is much more resistant to this problem than traditional lacquers, common sense is still advised. The problem most commonly happen when you have your guitar outside in below freezing weather for 15 to 20 minutes, (for instance, walking home with it) then immediately upon entering a warm room, opening the case to remove your guitar. Conversely, taking your guitar from a warm home out into an extremely low temperature may cause problems.

The solution to this problem is prevention. Keep your guitar in a cool place 7.2C to 10C (45F to 50F) for an hour or so before going out. The same rule applies when bringing your guitar in from the cold. Allow it to warm up gradually with the case closed for at least one hour. If possible, try not to take your guitar out in extremely frigid temperatures.

If, in spite of your best efforts, the finish on your guitar has checked, take heart. Although checking is permanent, it will not effect the life of the guitar or its playability or sound. It affects only the appearance.

To correct varnish checking would require a costly finishing job which, on top of not being covered by your warranty, may quite drastically affect the sound of the instrument. My recommendation would be to learn to live with the checks.

Another wintertime problem in relation to low humidity is the lifting of the bridge, actually quite common in the steel string guitar. Once more, the villain is shrinkage of the top. The bridge, whose grain runs the opposite direction to the grain of the top, cannot shrink in the same direction and, therefore, separates from the top with a shearing action. This is quite easily repaired by a competent repair person and is much less undesirable than cracking (which would occur in the top if the bridge did not let go under the developing tension).

The same tension can occur as the wood of the back and top shrink against the struts, and a shearing action may cause them to separate, resulting in internal buzzing and a structural weakening of the guitar. (This will happen more often to the back of the guitar, as the glue does not adhere to the rosewood of the back as it does to the spruce top.) Repair of this problem can become quite costly and is not covered by warranty.

To avoid most of these winter problems requires only the use of a little common sense.

One very important thing to remember is never to leave your guitar hanging on the wall in winter. The heat from a furnace rises. While floor temperatures may be 18C, five feet off the floor it may be 22C, and eight feet above the floor 27C! At that extreme temperature, the relative humidity becomes extremely low.

The winter time humidity in your home should be kept at approximately 45% relative to 22C for the safety of your guitar. If it dips too much lower, problems may begin.

Keep your guitar in the case when it is possible and in a cooler place and make use of Dampit or a similar device that retains water. These units should be checked every day in areas of extreme cold and low humidity.

These units contain a small amount of water and can be dry in the first eight hours or so. A word of caution: Don’t overdo a good thing and use too much moisture, or you will begin to observe the problems associated with excessive humidity.

 

Shipping

Winter or summer, it sometimes becomes necessary to ship your instrument by bus, plane or other mode of transportation. The following are a few tips to ensure a successful trip.

Proper packaging is an absolute necessity. Never ship your guitar in only its case. That is asking for trouble. I would suggest you go to your nearest music shop and ask for an empty cardboard shipping carton. They receive guitars in them all the time and, with any luck, you should be able to obtain one of them. The packaging should be crumpled newspaper, very loosely stuffed around the case. Take care not to overdo it as it is dangerous to wedge the case in too tight.

Here, I would like you to take note that it is not my recommendation to take the tension off the strings when shipping your guitar. This is a dangerous practice as the peghead with the machine heads and the neck are the heaviest part of the guitar. The string tension serves to balance this stress along with the length of the guitar. Without this tension, one good jar to the guitar and the guitar might arrive at its destination with the peghead sheared off at the nut. So, remember, when you are shipping, leave the tension on the strings. At least your neck stands a chance that way.

One helpful procedure is to crush some newspaper and stuff the space inside the case under the peghead lightly until the peghead sits slightly off the neck rest. This practice should reduce the chances of neck damage dramatically. A bit of a bonus from boxing your guitar is that the carton acts as insulation against a sudden rise or drop in temperature during shipment.

When your guitar is packed in a carton, it is not so obvious that it is a guitar, which cuts down on the chances of theft. You can put fragile, breakable or handle with care all over the carton, but never label it "Musical Instrument." Always insure your guitar for full value and always, when you receive a guitar, examine the carton and the instrument as carefully and as soon as possible. Do this while still in the baggage room or in the presence of the delivery person so, if the instrument is damaged, there is no question that it was damaged while in the carrier’s custody.

I hope this information has given you some insight into the character of your guitar, and some of the stresses and factors which can affect it. With close observation, common sense , loving care, and protection, your guitar should last a lifetime.

 

Jean Larrivee

Jean Larrivee